/73  )C 

J2.  - 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


I 

* 


••.** 


•'* 


.* 


MANUAL 


OF 


ELEMENTARY  GEOLOGY. 


By  the  same  Author. 

THE  PRINCIPLES  OF  GEOLOGY;  or,  the  MODEEN  CHANGES 
of  the  EARTH  and  its  INHABITANTS,  as  illustrative  of  Geology.  Ninth  and 
thoroughly  revised  Edition.  With  Woodcuts.  8vo.  18s. 

TRAVELS  IN  NORTH  AMERICA :  CANADA  and  NOVA  SCOTIA. 
With  GEOLOGICAL  OBSERVATIONS.  Second  Edition.  Maps  and  Plates.  2  vols. 
Post  8vo.  12s. 

A  SECOND  VISIT  TO  NORTH  AMERICA.  Third  Edition. 
2  vols.  Post  8vo.  12s. 


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MANUAL 


ELEMENTARY    GEOLOGY 


OR, 


THE   ANCIENT   CHANGES   OF   THE   EARTH  AND   ITS   INHABITANTS 
AS   ILLUSTRATED   BY  GEOLOGICAL   MONUMENTS. 


BY  SIR  CHARLES  LYELL,   M.A.  F.R.S. 

AUTHOR  OF   "PRINCIPLES  OF  GEOLOGY,"  ETC. 


"  It  is  a  philosophy  which  never  rests  — its  law  is  progress:  a  point  which  yesterday  was 
invisible  is  its  goal  to-day,  and  will  be  its  starting-post  to-morrow." 

JSDISBUKGH  REVIEW,  July,  1837. 


NUMliOLITE 


TERTIARY.  SECONDARY.  PRIMARY. 

FIFTH   EDITION,    GREATLY   ENLARGED,    AND    ILLUSTRATED    WITH   750    WOODCUTS. 

BOSTON: 
LITTLE,    BROWN,    AND    COMPANY. 

1855. 

The.  right  of  translation  is  reserved. 


PKEFACE   TO  THE  FIFTH  EDITION. 


IT  is  now  more  than  three  years  since  the  appearance  of  the 
last  Edition  of  the  Manual  (published  January,  1851).  In  that 
interval  the  science  of  Geology  has  been  advancing  as  usual 
at  a  rapid  pace,  making  it  desirable  to  notice  many  new  facts 
and  opinions,  and  to  consider  their  bearing  on  the  previ- 
ously acquired  stock  of  knowledge.  In  my  attempt  to  bring 
up  the  information  contained  in  this  Treatise  to  the  present 
state  of  the  science,  I  have  added  no  less  than  200  new  Illus- 
trations and  140  new  pages  of  Text,  which,  if  printed  separately 
and  in  a  less  condensed  form,  might  have  constituted  alone  a 
volume  of  respectable  size.  To  give  in  detail  a  list  of  all  the 
minor  corrections  and  changes  would  Jbe  tedious ;  but  I  have 
thought  it  useful,  in  order  to  enable  the  reader  of  former 
editions  to  direct  his  attention  at  once  to  what  is  new,  to 
offer  the  following  summary  of  the  more  important  additions 
and  alterations. 

Principal  Additions  and  Alterations  in  the  present  Edition. 

CHAP.  IX.  — "  The  general  Table  of  Fossiliferous  strata,"  for- 
merly placed  at  the  end  of  Chapter  XXVII.,  is  now  given  at 
p.  105.,  that  the  beginner  may  accustom  himself  from  the  first  to 
refer  to  it  from  time  to  time  when  studying  the  numerous  sub- 
divisions into  which  it  is  now  necessary  to  separate  the  chrono- 
logical series  of  rocks.  The  Table  has  been  enlarged  by  a  column 
of  Foreign  Equivalents,  comprising  the  names  and  localities  of  some 
of  the  best  known  strata  in  other  countries  of  contemporaneous  date 
with  British  Formations. 

CHAP.  XIV. — XVI.  —  The  classification  of  the  Tertiary  formations 
has  been  adapted  to  the  information  gained  by  me  during  a  tour 
made  in  the  summer  of  1851  in  France  and  Belgium.  The  results  of 
my  survey  were  printed  in  the  Quarterly  Journal  of  the  Geological 

A  3 


VI  PREFACE    TO   THE    FIFTH   EDITION. 

Society  of  London  for  1852.  In  the  course  of  my  investigations  I 
enjoyed  opportunities  of  determining  more  exactly  the  relations  of 
the  Antwerp  and  the  Suffolk  crag,  p.  174.;  the  stratigraphical  place 
of  the  Bolderberg  beds  near  Hasselt,  p.  179.;  that  of  the  Limburg 
or  Kleyn  Spawen  strata,  p.  189. ;  and  of  other  Belgian  and  French 
deposits.  In  reference  to  some  of  these,  the  questions  so  much  con- 
troverted of  late,  whether  certain  groups  should  be  called  Lower 
Miocene  or  Upper  Eocene,  are  fully  discussed,  p.  184.  et  seq. 

In  the  winter  of  1852, 1  had  the  advantage  of  examining  the  north- 
ern part  of  the  Isle  of  Wight,  in  company  with  my  friend  the  late 
lamented  Professor  Edward  Forbes,  who  pointed  out  to  me  the 
discoveries  he  had  just  made  in  regard  to  the  true  position  of  the 
Hempstead  series  (pp.  186  — 193.),  recognized  by  him  as  the  equi- 
valent of  the  Kleyn  Spawen  or  Limburg  beds,  and  his  new  views 
in  regard  to  the  relation  of  various  members  of  the  Eocene  series 
between  the  Hempstead  and  Bagshot  beds.  An  account  of  these 
discoveries,  with  the  names  of  the  new  subdivisions,  is  given  at 
pp.  209.  et  seq. ;  the  whole  having  been  revised  when  in  print  by 
Edward  Forbes. 

The  position  assigned  by  Mr.  Prestwich  to  the  Thanet  sands,  as 
an  Eocene  formation  inferior  to  the  Woolwich  beds,  is  treated  of 
at  p.  222.,  and  the  relations  of  the  Middle  and  Lower  Eocene  of 
France  to  various  deposits  in  the  Isle  of  Wight  and  Hampshire 
at  p.  223.  et  seq.  In  the  same  chapters,  many  figures  have  been 
introduced  of  characteristic  organic  remains,  not  given  in  previous 
editions. 

CHAP.  XVII. — In  speaking  of  the  Cretaceous  strata,  I  have  for 
the  first  time  alluded  to  the  position  of  the  Pisolitic  Limestone  in 
France,  and  other  formations  in  Belgium  intermediate  between  the 
White  Chalk  and  Thanet  beds,  p.  236. 

CHAP.  XVIII.  —  The  Wealden  beds,  comprising  the  Weald  Clay 
and  Hastings  Sands  apart  from  the  Purbeck,  are  in  this  chapter  for 
the  first  time  considered  as  belonging  to  the  Lower  Cretaceous 
Group,  and  the  reasons  for  the  change  are  stated  at  p.  264. 

CHAP.  XIX.  — Relates  to  "the  denudation  of  the  Weald,"  or  of 
the  country  intervening  between  the  North  and  South  Downs.  It 
has  been  almost  entirely  rewritten,  and  some  new  illustrations  in- 
troduced. Many  geologists  have  gone  over  that  region  again  and 
again  of  late  years,  bringing  to  light  new  facts,  and  speculating  on 
the  probable  time,  extent,  and  causes  of  so  vast  a  removal  of  rock. 
I  have  endeavoured  to  show  how  numerous  have  been  the  periods  of 
denudation,  how  vast  the  duration  of  some  of  them,  and  how  little 
the  necessity  to  despair  of  solving  the  problem  by  an  appeal  to  ordi- 
nary causation,  or  to  invoke  the  aid  of  imaginary  catastrophes  and 
paroxysmal  violence,  pp.  272 — 291. 

CHAP.  XX.— XXI. — On  the  strata  from  the  Oolite  to  the  Lias 
inclusive.  The  Purbeck  beds  are  here  for  the  first  time  considered 


PREFACE   TO   THE   FIFTH   EDITION.  Vll 

as  the  uppermost  member  of  the  Oolite,  in  accordance  with  the 
opinions  of  the  late  Professor  E.  Forbes,  p.  295.  Many  new  figures 
of  fossils  characteristic  of  the  subdivisions  of  the  three  Purbecks 
are  introduced;  and  the  discovery,  in  1854,  of  a  new  mammifer 
alluded  to,  p.  296. 

Representations  also  of  fossils  of  the  Upper,  Middle,  and  Lower 
Oolite,  and  of  the  Lias,  are  added  to  those  before  given. 

CHAP.  XXIL— XXIII. —  On  the  Triassic  and  Permian  forma- 
tions. The  improvements  consist  chiefly  of  new  illustrations  of 
fossil  remains. 

CHAP.  XXIV. — XXV.  —  Treating  of  the  Carboniferous  group, 
I  have  mentioned  the  subdivisions  now  generally  adopted  for  the 
classification  of  the  Irish  strata  (p.  362.),  and  I  have  added  new 
figures  of  fossil  plants  to  explain,  among  other  topics,  the  botanical 
characters  of  Calamites,  Sternbergia,  and  Trigonocarpum,  and  their 
relation  to  Conifers  (pp.  367,  368,  371.).  The  grade  also  of  the 
Coniferse  in  the  vegetable  kingdom,  and  whether  they  hold  a  high  or 
a  low  position  among  flowering  plants,  is  discussed  with  reference  to 
the  opinions  of  several  of  the  most  eminent  living  botanists ;  and  the 
bearing  of  these  views  on  the  theory  of  progressive  development, 
p.  373. 

The  casts  of  rain -prints  in  coal-shale  are  represented  in  several 
woodcuts  as  illustrative  of  the  nature  and  humidity  of  the  carboni- 
ferous atmosphere,  p.  384.  The  causes  also  of  the  purity  of  many 
seams  of  coal,  p.  385.,  and  the  probable  length  of  time  which  was 
required  to  allow  the  solid  matter  of  certain  coal-fields  to  accumulate, 
p.  386.,  are  discussed  for  the  first  time. 

Figures  are  given  of  Crustaceans  and  Insects  from  the  Coal,  pp. 
388,  389. ;  and  the  discovery  of  some  new  Reptiles  is  alluded  to, 
p.  405. 

I  have  also  alluded  to  the  causes  of  the  rarity  of  vertebrate  and 
invertebrate  air-breathers  in  the  coal,  p.  405. 

That  division  of  this  same  chapter  (Chap.  XXV.)  which  relates  to 
the  Mountain  Limestone  has  been  also  enlarged  by  figures  of  new 
fossils,  and  among  others  by  representations  of  Corals  of  the  Paleo- 
zoic, as  distinguishable  from  those  of  the  Neozoic,  type,  p.  407. ;  also 
by  woodcuts  of  several  genera  of  shells  which  retain  the  patterns 
of  their  original  colours,  p.  410.  The  foreign  equivalents  of  the 
Mountain  Limestone  are  also  alluded  to,  p.  413. 

CHAP.  XXVI.— In  speaking  of  the  Old  Red  Sandstone,  or  De- 
vonian Group,  the  evidence  of  the  occurrence  of  the  skeleton  of  a 
Reptile  and  the  footprints  of  a  Chelonian  in  that  series  are  recon- 
sidered, p.  416.  New  plants  found  in  Ireland  in  this  formation  are 
figured,  p.  418. ;  also  the  Pterygotus,  or  large  crustacean  of  Forfar- 
shire,  p.  419. ;  and,  lastly,  the  division  of  the  Devonian  series  in 
North  Devon  into  Upper,  Middle,  and  Lower,  p.  424.,  the  fossils  of 

A  4 


Vlii  PKEFACE    TO    THE   FIFTH   EDITION. 

the  same  (p.  425.  et  seq.\  and  the  equivalents  of  the  Devonian  beds 
in  Russia  and  the  United  States,  are  treated  of,  p.  429.  and  432. 

CHAP.  XXVJI. — The  classification  and  nomenclature  of  the  Si- 
lurian rocks  of  Great  Britain,  the  Continent  of  Europe,  and  North 
America,  and  the  question  whether  they  can  be  distinguished  from 
the  Cambrian,  and  by  what  paleontological  characters,  are  discussed 
in  this  chapter,  pp.  433.  451.  and  457. 

The  relation  of  the  Caradoc  Sandstone  to  the  Upper  and  Lower 
Silurian,  as  inferred  from  recent  investigations  (p.  441.),  the  vast 
thickness  of  the  Llandeilo  or  Lower  Silurian  in  Wales  (p.  446.),  the 
Obolus  or  Ungulite  grit  of  St.  Petersburg  and  its  fossils  (p.  447.),  the 
Silurian  strata  of  the  United  States  and  their  British  equivalents 
(p.  448.),  and  those  of  Canada,  the  discoveries  of  M.  Barrande  re- 
specting the  metamorphosis  of  Silurian  and  Cambrian  trilobites 
(pp.  445.  454.),  are  among  the  subjects  enlarged  upon  more  fully 
than  in  former  editions,  or  now  treated  of  for  the  first  time. 

The  Cambrian  beds  below  the  Llandeilo,  and  their  fossils,  are  like- 
wise described  as  they  exist  in  Wales,  Ireland,  Bohemia,  Sweden, 
the  United  States,  and  Canada,  and  some  of  their  peculiar  organic 
remains  are  figured,  p.  451.  to  p.  457. 

Lastly,  at  the  conclusion  of  the  chapter,  some  remarks  are  offered 
respecting  the  absence  of  the  remains  of  fish  and  other  vertebrata 
from  the  deposits  below  the  Upper  Silurian,  p.  457.,  in  elucidation  of 
which  topic  a  Table  has  been  drawn  up  of  the  dates  of  the  successive 
discovery  of  different  classes  of  Fossil  Vertebrata  in  rocks  of  higher 
and  higher  antiquity,  showing  the  gradual  progress  made  in  the 
course  of  the  last  century  and  a  half  in  tracing  back  each  class  to 
more  and  more  ancient  rocks.  The  bearing  of  the  positive  and 
negative  facts  thus  set  forth  on  the  doctrine  of  progressive  develop- 
ment is  then  discussed,  and  the  grounds  of  the  supposed  scarcity 
both  of  vertebrate  and  invertebrate  air-breathers  in  the  most  ancient 
formation  considered,  p.  460. 

CHAP.  XXVIII.  —  With  the  assistance  of  an  able  mineralogist, 
M.  Delesse,  I  have  revised  and  enlarged  the  glossary  of  the  more 
abundant  volcanic  rocks,  p.  476.,  and  the  table  of  analyses  of  simple 
minerals,  p.  479. 

CHAP.  XXIX.  —  In  consequence  of  a  geological  excursion  to 
Madeira  and  the  Canary  Islands,  which  I  made  in  the  winter  of 
1853-4,  I  have  been  enabled  to  make  larger  additions  of  original 
matter  to  this  chapter  than  to  any  other  in  the  work.  The  account 
of  Teneriffe  and  Madeira,  pp.  514.  522.,  is  wholly  new.  Formerly  I 
gave  an  abstract  of  Von  Buch's  description  of  the  island  of  Palma, 
one  of  the  Canaries,  but  I  have  now  treated  of  it  more  fully  from 
my  own  observations,  regarding  Palma  as  a  good  type  of  that  class 
of  volcanic  mountains  which  have  been  called  by  Von  Buch 
"  craters  of  elevation,"  pp.  498 — 512.  Many  illustrations,  chiefly 
from  the  pencil  of  my  companion  and  fellow -labourer,  Mr.  Hartung, 
have  been  introduced.  In  reference  to  the  above-mentioned  sub- 


PREFACE  TO   THE   FIFTH    EDITION.  ix 

jects,   citations   are  made   from   Dana  on  the    Sandwich   Islands, 
p.  493.,  and  from  Junghuhn's  Java,  p.  496. 

CHAP.  XXXV.— XXXVII.  —  The  theory  of  the  origin  of  the 
metamorphic  rocks  and  certain  views  recently  put  forward  by  some 
geologists  respecting  cleavage  and  foliation  have  made  it  desirable 
to  recast  and  rewrite  A  portion  of  these  chapters.  New  proofs  are 
cited  in  favour  of  attributing  cleavage  to  mechanical  force,  p.  610., 
and  for  inferring  in  many  cases  a  connection  between  foliation  and 
cleavage,  p.  615.  At  the  same  time,  the  question — how  far  the 
planes  of  foliation  usually  agree  with  those  of  sedimentary  depo- 
sition, is  entered  into,  p.  614. 

CHAP.  XXXVni.  —  To  the  account  formerly  published  of  mineral 
veins  some  facts  and  opinions  are  added  respecting  the  age  of  the 
rocks  and  alluvial  deposits  containing  gold  in  South  America,  the 
United  States,  California,  and  Australia. 


I  have  already  alluded  to  the  assistance  afforded  me  by  the 
late  Professor  Edward  Forbes  towards  the  improvement  of 
some  parts  of  this  work.  His  letters  suggesting  corrections 
and  additions  were  continued  to  within  a  few  weeks  of  his 
sudden  and  unexpected  death,  and  I  felt  most  grateful  to  him 
for  the  warm  interest,  which,  in  the  midst  of  so  many  and 
pressing  avocations,  he  took  in  the  success  of  my  labours.  His 
friendship  and  the  power  of  referring  te  his  sound  judgment  in 
cases  of  difficulty  on  palaeontological  and  other  questions  were 
among  the  highest  privileges  I  have  ever  enjoyed  in  the  course 
of  my  scientific  pursuits.  Never  perhaps  has  it  been  the  lot  of 
any  Englishman,  who  had  not  attained  to  political  or  literary 
eminence,  more  especially  one  who  had  not  reached  his  fortieth 
year,  to  engage  the  sympathies  of  so  wide  a  circle  of  admirers, 
and  to  be  so  generally  mourned.  The  untimely  death  of  such 
a  teacher  was  justly  felt  to  be  a  national  loss ;  for  there  was  a 
deep  conviction  in  the  minds  of  all  who  knew  him,  that  genius 
of  so  high  an  order,  combined  with  vast  acquirements,  true 
independence  of  character,  and  so  many  social  and  moral  ex- 
cellencies, would  have  inspired  a  large  portion  of  the  rising 
generation  with  kindred  enthusiasm  for  branches  of  knowledge 
hitherto  neglected  in  the  education  of  British  youth. 

As  on  former  occasions,  I  shall  take  this  opportunity  of 
stating  that  the  "  Manual "  is  not  an  epitome  of  the  "  Principles 
of  Geology,"  nor  intended  as  introductory  to  that  work.  So 
much  confusion  has  arisen  on  this  subject,  that  it  is  desirable 


X  PREFACE    TO   THE   FIFTH   EDITION. 

to  explain  fully  the  different  ground  occupied  by  the  two  pub- 
lications. The  first  five  editions  of  the  "  Principles  "  comprised 
a  4th  book,  in  which  some  account  was  given  of  systematic  geo- 
logy, and  in  which  the  principal  rocks  composing  the  earth's 
crust  and  their  organic  remains  were  described.  In  subsequent 
editions  this  4th  book  was  omitted,  it  haVing  been  expanded, 
in  1838,  into  a  separate  treatise  called  the  "  Elements  of  Geo- 
logy," first  re-edited  in  1842,  and  again  recast  and  enlarged  in 
1851,  and  entitled  "  A  Manual  of  Elementary  Geology. "  Of 
this  enlarged  work  another  edition,  called  the  Fourth,  was 
published  in  1852. 

Although  the  subjects  of  both  treatises  relate  to  Geology,  as 
their  titles  imply,  their  scope  is  very  different ;  the  "  Principles  " 
containing  a  view  of  the  modern  changes  of  the  earth  and  its 
inhabitants,  while  the  "  Manual "  relates  to  the  monuments  of 
ancient  changes.  In  separating  the  one  from  the  other,  I  have 
endeavoured  to  render  each  complete  in  itself,  and  independent ; 
but  if  asked  by  a  student  which  he  should  read  first,  I  would 
recommend  him  to  begin  with  the  "  Principles,"  as  he  may 
then  proceed  from  the  known  to  the  unknown,  and  be  provided 
beforehand  with  a  key  for  interpreting  the  ancient  phenomena, 
whether  of  the  organic  or  inorganic  world,  by  reference  to 
changes  now  in  progress. 

It  will  be  seen  on  comparing  "  The  Contents  "  of  the  "  Prin- 
ciples "  with  the  abridged  headings  of  the  chapters  of  the  pre- 
sent work  (see  the  following  pages),  that  the  two  treatises  have 
but  little  in  common ;  or,  to  repeat  what  I  have  said  in  the 
Preface  to  the  "  Principles,"  they  have  the  same  kind  of  con- 
nection which  Chemistry  bears  to  Natural  Philosophy,  each 
being  subsidiary  to  the  other,  and  yet  admitting  of  being  con- 
sidered as  different  departments  of  science.* 

CHARLES  LYELL. 

53.  Harley  Street,  London,  February  22.  1855. 

*  As  it  is  impossible  to  enable  the  reader  to  recognize  rocks  and  minerals  at 
sight  by  aid  of  verbal  descriptions  or  figures,  he  will  do  well  to  obtain  a  well- 
arranged  collection  of  specimens,  such  as  may  be  procured  from  Mr.  Tennant  (149. 
Strand),  teacher  of  Mineralogy  at  King's  College,  London. 


CONTENTS. 


CHAPTER  I.  —  On  the  different  Classes  of  Rocks. 

Geology  defined  —  Successive  formation  of  the  earth's  crust  —  Classification  of  rocks 

.    according  to  their  origin   and  age  —  Aqueous  rocks  —  Volcanic  rocks  —  Plutonic 

rocks  —  Metamorphic  rocks  —  The  term  primitive,  why  erroneously  applied  to  the 

crystalline  formations       -  -  -         Page  1 

CHAPTER  II.  —  Aqueous  Rocks  —  TJieir  Composition  and  Forms  of  Stratification. 

Mineral  composition  of  strata  —  Arenaceous  rocks  —  Argillaceous  —  Calcareous  — 
Gypsum  —  Forms  of  stratification  —  Diagonal  arrangement  —  Ripple-mark  -  10 

CHAPTER  III.  —  Arrangement  of  Fossils  in  Strata  —  Freshwater  and  Marine. 

Limestones  formed  of  corals  and  shells  —  Proofs  of  gradual  increase  of  strata  derived 
from  fossils  —  Tripoli  and  semi-opal  formed  of  infusoria  —  Chalk  derived  principally 
from  organic  bodies  —  Distinction  of  freshwater  from  marine  formations  —  Alter- 
nation of  marine  and  freshwater  deposits  -  21 

CHAPTER  IV.  —  Consolidation  of  Strata  and  Petrifaction  of  Fossils. 

Chemical  and  mechanical  deposits — Cementing  together  of  particles  —  Concretionary 
nodules  —  Consolidating  effects  of  pressure  —  Mineralization  *of  organic  remains  — 
Impressions  and  casts  how  formed  —  Fossil  wood  —  Source  of  lime  and  silex  in 
solution  ----------33 

CHAPTER  V.  —  Elevation  of  Strata  above  the  Sea  —  Horizontal  and  Inclined 
Stratification. 

Position  of  marine  strata,  why  referred  to  the  rising  up  of  the  land,  not  to  the  going 
down  of  the  sea  —  Upheaval  of  horizontal  strata  —  Inclined  and  vertical  stratification 

—  Anticlinal  and  synclinal  lines  —  Theory  of  folding  by  lateral  movement  —  Creeps 

—  Dip  and  strike  —  Structure  of  the  Jura  —  Inverted  position  of  disturbed  strata  — 
Unconformable  stratification  —  Fractures  of  strata  —  Faults       -  -  -44 

CHAPTER  VI.  —  Denudation. 

Denudation  defined  —  Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in  the 
earth's  crust  —  Levelled  surface  of  countries  in  which  great  faults  occur  —  Denuding 
power  of  the  ocean  —  Origin  of  Valleys  —  Obliteration  of  sea-cliffs —  Inland  sea-cliffs 
and  terraces  -  .  *'  -  -  -  -  66 

CHAPTER  VII.  —  Alluvium. 

Alluvium  described  —  Due  to  complicated  causes  —  Of  various  ages  —  How  distin- 
guished from  rocks  in  situ — River-terraces  —  Parallel  roads  of  Glen  Roy  -  '  79 

CHAPTER  VIII. —  Clironological  Classification  of  Rocks. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically  — 
Lehman's  division  into  primitive  and  secondary  —  Werner's  addition  of  a  transition 
class  —  Neptunian  theory  —  Hutton  on  igneous  origin  of  granite — The  name  of 
"primary"  for  granite  and  the  term  "transition"  why  faulty  —  Chronological  no- 
menclature adopted  in  this  work,  so  far  as  regards  primary,  secondary,  and  ter- 
tiary periods  -----_.  -89 


Xll  CONTENTS. 

CHAPTER  IX.  —  On  the  different  Ages  of  the  Aqueous  Rocks. 

On  the  three  tests  of  relative  age  —  superposition,  mineral  character,  and  fossils  — 
Change  of  mineral  character  and  fossils  in  the  same  formation  —  Proofs  that  distinct 
species  of  animals  and  plants  have  lived  at  successive  periods  —  Distinct  provinces 
of  indigenous  species  —  Similar  laws  prevailed  at  successive  geological  periods — 
Test  of  age  by  included  fragments  —  Frequent  absence  of  strata  of  intervening 
periods  —  General  Table  of  Fossiliferous  strata  -  -  Page  96 

CHAPTER  X.  —  Classification  of  Tertiary  Formations.  —  Post  Pliocene  Group. 

General  principles  of  classification  of  tertiary  strata  —  Difficulties  in  determining  their 
chronology  —  Increasing  proportion  of  living  species  of  shells  in  strata  of  newer  origin 

—  Terms  Eocene,  Miocene,  and  Pliocene — Post-Pliocene  recent  strata  -  -    104 

CHAPTER  XI.  —  Newer  Pliocene  Period.  —  Boulder  Formation. 

Drift  of  Scandinavia,  northern  Germany,  and  Russia — Fundamental  rocks  polished, 
grooved,  and  scratched  —  Action  of  glaciers  and  icebergs  —  Fossil  shells  of  glacial 
period — Drift  of  eastern  Norfolk — Ancient  glaciers  of  North  Wales — Irish  drift  -  121 

CHAPTER  XII. — Boulder  Formation — continued. 

Effects  of  intense  cold  in  augmenting  the  quantity  of  alluvium  —  Analogy  of  erratics 
and  scored  rocks  in  North  America,  Europe,  and  Canada  —  Why  organic  remains  so 
rare  in  northern  drift  —  Many  shells  and  some  quadrupeds  survived  the  glacial 
cold  —  Alps  an  independent  centre  of  dispersion  of  erratics  —  Meteorite  in  Asiatic 
drift  -  -  131 

CHAPTER  XIII.  —  Newer  Pliocene  Strata  and  Cavern  Deposits. 

Pleistocene  formations  —  Freshwater  deposits  in  valley  of  Thames  —  In  Norfolk  cliffs  — 
In  Patagonia  —  Comparative  longevity  of  species  in  the  mammalia  and  testacea  — 
Crag  of  Norwich  —  Newer  Pliocene  strata  of  Sicily  —  Osseous  breccias  and  cavern- 
deposits  —  Sicily  —  Kirkdale  —  Australian  cave-breccias  —  Relationship  of  geogra- 
phical provinces  of  living  vertebrata  and  those  of  Pliocene  species — Teeth  of  fossil 
quadrupeds  -  ....  ^.  .  146 

CHAPTER  XIV.  —  Older  Pliocene  and  Miocene  Formations. 

Red  and  Coralline  crags  of  Suffolk  —  Fossils,  and  proportion  of  recent  species  —  Depth 
of  sea,  and  climate  —  Migration  of  many  species  of  shells  southwards  during  the  gla- 
cial period  —  Antwerp  crag  —  Subapennine  beds  —  Miocene  formations  —  Faluns  of 
Touraine  —  Depth  of  sea  and  littoral  character  of  fauna  —  Climate  —  Proportion  of 
recent  species  of  shells  —  Miocene  strata  of  Bordeaux,  Belgium,  and  North  Germany 

—  Older  Pliocene  and  Miocene  formations  in  the  United  States  —  Sewalik  Hills  in 
India         -  -  -  161 

CHAPTER  XV. —  Upper  Eocene  Formations.    (Lower  Miocene  of  many  authors.) 

Remarks  on  classification,  and  on  the  line  of  separation  between  Eocene  and  Miocene  — 
Whether  the  Limburg  strata  in  Belgium  should  be  called  Upper  Eocene — Strata  of 
same  age  in  North  Germany — Mayence  basin  —  Brown  Coal  of  Germany — Upper 
Eocene  of  Isle  of  Wight  —  Of  France  — Lacustrine  strata  of  Auvergne  and  the  Cantal 

—  Upper  Eocene  of  Bordeaux,  &c.  —  Of  Nebraska,  United  States  -  184 

•      CHAPTER  XVI.  —  Middle  and  Lower  Eocene  Formations. 

Middle  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  Mammalia — Fossils  of  Barton  Clay  —  Of 
the  Bagshot  and  Bracklesham  beds  —  Lower  Eocene  strata  of  England  —  London 
Clay  proper  —  Strata  of  Kyson  in  Suffolk — Fossil  monkey  and  opossum  —  Plastic 
clays  and  sands  —  Thanet  sands  —  Middle  and  Lower  Eocene  formations  of  France  — 
Nummulitic  formations  of  Europe  and  Asia  —  Eocene  strata  at  Claiborne,  Alabama 

—  Colossal  cetacean  —  Orbitoid  limestone  —  Burr  stone  -  208 


CONTENTS.  Xlll 


CHAPTER  XVII.  —  Cretaceous  Group. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods  —  Formations  in  Belgium 
and  France  of  intermediate  age  —  Pisolitic  limestone  —  Divisions  of  the  Cretaceous 
series  in  North-Western  Europe  —  Maestricht  beds  — Chalk  of  Faxoe  —  White  chalk 
—How  far  derived  from  shells  and  corals  — Chalk  flints  —  Fossils  of  the  Upper 
Cretaceous  rocks  —  Upper  Greensand  and  Gault — Chalk  of  South  of  Europe  —  Hip- 
purite  limestone  —  Cretaceous  rocks  of  the  United  States  -  -  Page  235 

CHAPTER  XVIII.  —  Lower  Cretaceous  and  Wealden  Formations. 

Lower  Greensand  —  Term  "Neocomian"  —  Fossils  of  Lower  Greensand  —  Wealden 
formation  —Weald  Clay  and  Hastings  Sand  —  Fossil  shells  and  fish  —Their  relation 
to  the  Cretaceous  type  —  Flora  of  Lower  Cretaceous  and  Wealden  periods  -  -  257 

CHAPTER  XIX.  —  Denudation  of  the  Chalk  and  Wealden. 

Physical  geography  of  certain  districts  composed  of  Cretaceous  and  Wealden  strata  — 
Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy— Denudation  of  the  chalk  and 
wealden  in  Surrey,  Kent,  and  Sussex  — Chalk  once  continuous  from  the  North  to  the 
South  Downs  —  Rise  and  denudation  of  the  strata  gradual  —  At  what  period  the 
Weald  valley  was  denuded,  and  by  what  causes  —  Elephant-bed,  Brighton  —  San- 
gatte cliff— Conclusion  -  -  -268 

CHAPTER  XX.  —  Jurassic  Group. — Purbeck  Beds  and  Oolite. 

The  Purbeck  beds  a  member  of  the  Upper  Oolite  — New  fossil  Mammifer— Dirt-bed  — 
Fossils  of  the  Purbeck  beds  —  Portland  stone  and  fossils  —  Middle  Oolite  —  Coral  Rag 
—  Zoophytes  —  Nerinaean  limestone  —  Diceras  limestone  —  Oxford  Clay,  Ammonites 
and  Belemnites  —  Lower  Oolite,  Crinoideans  —  Great  Oolite  —  Stonesfield  Slate  — 
Fossil  mammalia  —  Yorkshire  Oolitic  coal-field  —  Brora  coal  —  Fuller's  Earth  —  In- 
ferior Oolite  and  fossils  -  -  -  -  -  -  -  -292 


CHAPTER  XXI.  —  Jurassic  Group,  continued. —  Lias. 

Mineral  character  of  Lias  —  Fossil  shells  and  fish  —  Radiata  —  Ichthyodorulites  — 
Reptiles  —  Ichthyosaur  and  Plesiosaur  —  Fluyio-marine  beds  in  Gloucestershire,  and 
Insect  limestone — Fossil  plants  —  Origin  of  the  Oolite  and  Lias  —  Oolitic  coal-field 
of  Virginia  •  ...  318 

CHAPTER  XXII.  —  Trias  or  New  Red  Sandstone  Group. 

Distinction  between  New  and  Old  Red  Sandstone  —  The  Trias  and  its  three  divisions 
in  Germany  —  Keuper  and  its  fossils — Muschelkalk  and  fossils  —  Fossil  plants  of 
the  Bunter  —  Triassic  group  in  England  —  Footsteps  of  Cheirotherium —  Osteology  of 
the  Labyrinthodon  —  Triassic  mammifer  —  Origin  of  Red  Sandstone  and  Rock-salt  — 
New  Red  Sandstone  in  the  United  States  —  Fossil  footprints  of  birds  and  reptiles  in 
the  valley  of  the  Connecticut  -  -  -334 

CHAPTER  XXIII.  —  Permian  or  Magnesian  Limestone  Group. 

Fossils  of  Magnesian  Limestone  —  Term  Permian  —  English  and  German  equivalents  — 
Marine  shells  and  corals  —  Palaeoniscus  and  other  fish  —  Thecodont  saurians  — 
Permian  Flora  —  Its  generic  affinity  to  the  carboniferous  —  Psaronites  or  tree- 
ferns  -  ...  -  353 

CHAPTER  XXIV.  —  The  Coal,  or  Carboniferous  Group. 

Carboniferous  strata  in  England  —  Coal-measures  and  Mountain  limestone  —  Carboni- 
ferous series  in  Ireland  and  South  Wales  —  Underclays  with  Stigmaria  —  Carboni- 


XIV  CONTENTS. 

ferous  Flora  —  Ferns,  Lepidodendra,  Calamites,  Sigillarias  —  Coniferse  —  Sternbergia 

—  Trigonocarpon  —  Grade  of  Coniferae  in  the  Vegetable  Kingdom  —  Absence  of 
Angiosperras  —  Coal,  how  formed  —  Erect  fossil  trees  —  Rain-prints  —  Purity  of  the 
Coal  explained — Time  required  for  its  accumulation — Crustaceans  and  insects 

Page  361 

CHAPTER  XXV.  —  Carboniferous  Group  —  continued. 

Coal-fields  of  the  United  States  —  Section  of  the  country  between  the  Atlantic  and 
Mississippi — Uniting  of  many  coal-seams  into  one  thick  bed  —  Vast  extent  and 
continuity  of  single  seams  of  coal — Ancient  river-channel  in  Forest  of  Dean  coal- 
field —  Climate  of  Carboniferous  period  —  Insects  in  coal  —  Great  number  of  fossil  fish 
— First  discovery  of  the  skeletons  of  fossil  reptiles  —  First  land-shell  of  the  Coal  found 

—  Rarity  of  air-breathers,  whether  vertebrate  or  invertebrate,  in  Coal-measures  — 
Mountain  limestone  —  Its  corals  and  marine  shells  -  -  -  -  391 


CHAPTER  XXVI.  —  Old  Red  Sandstone  or  Devonian  Group. 

Old  Red  Sandstone  of  the  borders  of  Wales  —  Scotland  and  the  South  of  Ireland  — 
Fossil  reptile  of  Elgin  —  Fossil  Devonian  plants  at  Kilkenny  —  Ichthyolites  of 
Clashbinnie  —  Fossil  fish,  &c.,  crustaceans,  of  Caithness  and  Forfarshire  —  Distinct 
lithological  type  of  Old  Red  in  Devon  and  Cornwall — Term  "  Devonian  " — Devonian 
series  of  England  and  the  Continent  —  Old  Red  Sandstone  of  Russia  —  Devonian 
strata  of  the  United  States  -  -  415 

CHAPTER  XXVII.  —  Silurian  and  Cambrian  Groups. 

Silurian  strata  formerly  called  "  Transition  "  —  Subdivisions  —  Ludlow  formation  and 
fossils  —  Ludlow  bone-bed,  and  oldest  known  remains  of  fossil  fish  —  Wenlock  form- 
ation, corals,  cystideans,  trilobites — Caradoc  sandstone — Pentameri  and  Tentaculites 
—  Lower  Siluriank  rocks  —  Llandeilo  flags  —  Cystideae  —  Trilobites  —  Graptolites  — 
Vast  thickness  of  Lower  Silurian  strata  in  Wales  —  Foreign  Silurian  equivalents  in 
Europe  —  Ungulite  grit  of  Russia  —  Silurian  strata  of  the  United  States  —  Canadian 
equivalents  —  Deep-sea  origin  of  Silurian  strata  —  Fossiliferous  rocks  below  the 
Llandeilo  beds  —  Cambrian  group  —  Lingula  flags  —  Lower  Cambrian  —  Oldest 
known  fossil  remains  —  "  Primordial  group  "  of  Bohemia  —  Metamorphosis  of  trilo- 
bites—  Alum  schists  of  Sweden  and  Norway  —  Potsdam  sandstone  of  United  States 
and  Canada — Trilobites  on  the  Upper  Mississippi  —  Supposed  period  of  invertebrate 
animals  —  Absence  of  fish  in  Lower  Silurian  —  Progressive  discovery  of  vertebrata 
in  older  rocks  —  Doctrine  of  the  non-existence  of  vertebrata  in  the  older  fossiliferous 
periods  premature  ___..._.  433 


CHAPTER  XXVIII.  —  Volcanic  Rocks. 

Trap  rocks  —  Name,  whence  derived  —  Their  igneous  origin  at  first  doubted  —  Their 
general  appearance  and  character  —  Mineral  composition  and  texture  —  Varieties  of 
felspar  —  Hornblende  and  augite  —  Isomorphism  —  Rocks,  how  to  be  studied  — 
Basalt,  trachyte,  greenstone,  porphyry,  scoria,  amygdaloid,  lava,  tuff — Agglomerate 
— Laterite  —  Alphabetical  list,  and  explanation  of  names  and  synonyms  of  volcanic 
rocks  —  Table  of  the  analyses  of  minerals  most  abundant  in  the  volcanic  and  hypo- 
gene  rocks  ...--•.,...  •  ~  ~  -  -  '-...--  -464 

CHAPTER  XXIX.  —  Volcanic  Rocks— continued. 

Trap  dikes— Strata  altered  at  or  near  the  contact  —  Conversion  of  chalk  into  marble 

—  Trap  interposed  between  strata  —  Columnar  and  globular  structure— Relation  of 
trappean  rocks  to  the  products  of  active  volcanos  —  Form,  external  structure,  and 
origin  of  volcanic  mountains — Craters  and  Calderas  —  Sandwich  Islands  —  Lava 
flowing  underground  —  Truncation  of  cones  —  Javanese  Calderas  —  Canary  Islands 

—  Structure  and  origin  of  the  caldera  of  Palma  —  Aqueous  conglomerate  in  Palma 

—  Hypothesis  of  upheaval  considered  —  Slope  on  which  stony  lavas  may  form  — 


CONTENTS.  XV 

Island  of  St.  Paul  in  the  Indian  Ocean  —  Peak  of  Teneriffe,  and  ruins  of  older  cone 

—  Madeira  —  Its  volcanic  rocks,  partly  of  marine,  and  partly  of  subaerial  origin  — 
Central  axis  of  eruptions — Varying  dip  of  solid  lavas  near  the  axis,  and  further  from 
it  —  Leaf-bed  and  fossil  land-plants  —  Central  valleys  of  Madeira  how  formed 

Page  480 

CHAPTER  XXX.  —  On  the  Different  Ages  of  the  Volcanic  Rocks. 

Tests  of  relative  age  of  volcanic  rocks  —  Test  by  superposition  and  intrusion  —  Test  by 
alteration  of  rocks  in  contact — Test  by  organic  remains  — Test  of  age  by  mineral  cha- 
racter—  Test  by  included  fragments — Volcanic  rocks  of  the  Post-Pliocene  period  — 
Basalt  of  Bay  of  Trezza  in  Sicily  —  Post-Pliocene  volcanic  rocks  near  Naples  — 
Dikes  of  Somma  —  Igneous  formations  of  the  Newer  Pliocene  period  —  Val  di  Noto 
in  Sicily 523 

CHAPTER  XXXI.  —  On  the  different  Ages  of  the  Volcanic  Eocks— continued. 

Volcanic  rocks  of  the  Older  Pliocene  period  —  Tuscany  —  Rome  —  Volcanic  region  of 
Olot  in  Catalonia  —  Cones  and  lava-currents  —  Miocene  period  —  Brown-coal  of  the 
Eifel  and  contemporaneous  trachytic  rocks  —  Age  of  the  brown-coal  —  Peculiar  cha- 
racters of  the  volcanos  of  the  Upper  and  Lower  Eifel — Lake  craters  —  Trass— Hun- 
garian volcanos  -  ._..__  535 

CHAPTER  XXXII.  —  On  the  different  Ages  of  the  Volcanic  Rocks  —  continued. 

Volcanic  rocks  of  the  Pliocene  and  Miocene  periods  continued  —  Auvergne  —  Mont  Dor 

—  Breccias  and  alluviums  of  Mont  Perrier,  with  bones  of  quadrupeds  —  Mont  Dome 

—  Cones  not  denuded  by  general  flood  —  Velay  —  Bones  of  quadrupeds  buried  in 
scoriae  —  Cantal  —  Eocene  volcanic  rocks  —  Tuffs  near  Clermont  —  Hill  of  Gergovia  — 
Trap  of  Cretaceous  period  —  Oolitic  period — New  Red  Sandstone  period  —  Carboni- 
ferous period  —  Old  Red  Sandstone  period  —  Silurian  period  —  Cambrian  volcanic 
rocks         -  -  -  -  -  550 

CHAPTER  XXXIII.  —  Plutonic  Rocks—  Granite. 

General  aspect  of  granite  —  Analogy  and  difference  of  volcanic  and  plutonic  formations 

—  Minerals  in  granite  —  Mutual  penetration  of  crystals  of  quartz  and  felspar — 
Syenitic,  talcose,  and  schorly  granites  —  Eurite — Passage  of  granite  into  trap  — 
Granite  veins  in  Glen  Tilt,  and  other  countries  —  Composition  of  granite  veins  — 
Metalliferous  veins  in  strata  near  their  junction  with  granite  —  Quartz  veins  —  Whe- 
ther plutonic  rocks  are  ever  overlying  —  Their  exposure  at  the  surface  due  to 
denudation  _________  555 

CHAPTER  XXXIV.  —  On  the  different  Ages  of  the  Plutonic  Rocks. 

Difficulty  in  ascertaining  the  age  of  a  plutonic  rock  —  Test  of  age  by  relative  position 

—  Test  by  intrusion  and  alteration  —  Test  by  mineral  composition  —  Test  by  included 
fragments  —  Recent  and  Pliocene  plutonic  rocks,  why  invisible  —  Tertiary  plutonic 
rocks  in  the  Andes  —  Granite  altering  Cretaceous  rocks  —  Granite  altering  Lias  — 
Granite  altering  Carboniferous  strata  —  Granite  of  the  Old  Red  Sandstone  period  — 
Syenite  altering  Silurian  strata  in  Norway  —  Oldest  plutonic  rocks  —  Granite  pro- 
truded in  a  solid  form  —  Age  of  the  granites  of  Arran,  in  Scotland         -  -  579 

CHAPTER  XXXV.  —  Metamorphic  Rocks. 

General  character  of  metamorphic  rocks  —  Gneiss — Hornblende-schist — Mica-schist — 
Clay-slate  —  Quartzite  —  Chlorite-schist  —  Metamorphic  limestone  —  Alphabetical 
list  and  explanation  of  the  more  abundant  rocks  of  this  family  —  Origin  of  the 
metamorphic  strata  —  Their  stratification  —  Fossiliferous  strata  near  intrusive  masses 
of  granite  converted  into  different  members  of  the  metamorphic  series  —  Objections 
to  the  metamorphic  theory  considered  —  Partial  conversion  of  Eocene  slate  into 
gneiss  .-.---..  --  594 


XVI  CONTENTS. 

CHAPTER  XXXVI.  —  Metamorphic  Rocks — continued. 

Origin  of  the  metamorphic  rocks,  continued  —  Definition  of  joints,  slaty  cleavage,  and 
foliation  —  Causes  of  these  structures  —  Mechanical  theory  of  cleavage  — Supposed 
combination  of  crystalline  and  mechanical  forces  —  Lamination  of  some  volcanic 
rocks  due  to  motion  —  Whether  the  foliation  of  the  crystalline  schists  be  usually 
parallel  with  the  original  planes  of  stratification  -  Page  607 

CHAPTER  XXXVII.—  On  the  different  Ages  of  tJte  Metamorphic  Rocks. 

Age  of  each  set  of  metamorphic  strata  twofold  —  Test  of  age  by  fossils  and  mineral 
character  not  available  —  Test  by  superposition  ambiguous  —  Conversion  of  fossili- 
ferous  strata  into  metamorphic  rocks  —  Limestone  and  shale  of  Carrara  —  Metamor- 
phic strata  older  than  the  Cambrian  rocks  —  Others  of  Lower  Silurian  origin  — Others 
of  the  Jurassic  and  Eocene  periods  —  Why  scarcely  any  of  the  visible  crystalline 
strata  are  very  modern  —  Order  of  succession  in  metamorphic  rocks  —  Uniformity  of 
mineral  character — Why  the  metamorphic  strata  are  less  calcareous  than  the 
fossiliferous  ....  .  _  618 

CHAPTER  XXXVIII.  —  Mineral  Veins. 

Werner's  doctrine  that  mineral  veins  were  [fissures  filled  from  above  —  Veins  of  segre- 
gation—  Ordinary  metalliferous  veins  or  lodes  —  Their  frequent  coincidence  with 
faults  —  Proofs  that  they  originated  in  fissures  in  solid  rock  —  Veins  shifting  other 
veins — Polishing  of  their  walls  or  "  slicken-sides  " —  Shells  and  pebbles  in  lodes  — 
Evidence  of  the  successive  enlargement  and  reopening  of  veins  —  Why  some  veins 
alternately  swell  out  and  contract  —  Filling  of  lodes  by  sublimation  from  below — 
Chemical  and  electrical  action  —  Relative  age  of  the  precious  metals  —  Copper  and 
lead  veins  in  Ireland  older  than  Cornish  tin  —  Lead  veins  in  Lias,  Glamorganshire — 
Gold  in  Russia,  California,  and  Australia  —  Connection  of  hot  springs  and  mineral 
veins — Concluding  remarks  -....__  g26 


MANUAL 


OF 


ELEMENTARY    GEOLOGY, 


CHAPTER  I. 

ON   THE   DIFFERENT  CLASSES   OF   ROCKS. 

Geology  defined—  Successive  formation  of  the  earth's  crust — Classification  of  rocks 
according  to  their  origin  and  age  —  Aqueous  rocks — Their  stratification  and  im- 
bedded fossils — Volcanic  rocks,  with  and  without  cones  and  craters — Plutonic 
rocks,  and  their  relation  to  the  volcanic — Metamorphic  rocks,  and  their  probable 
origin — The  term  primitive,  why  erroneously  applied  to  the  crystalline  formations 
— Leading  division  of  the  work. 

OF  what  materials  is  the  earth  composed,  and  in  what  manner  are 
these  materials  arranged  ?  These  are  the  first  inquiries  with  which 
Geology  is  occupied,  a  science  which  derives  its  name  from  the  Greek 
yrj,  ge,  the  earth,  and  Xoyoc,  logos,  a  discourse.  Previously  to  experience 
we  might  have  imagined  that  investigations  of  this  kind  would  relate 
exclusively  to  the  mineral  kingdom,  and  to  the  various  rocks,  soils, 
and  metals,  which  occur  upon  the  surface  of  the  earth,  or  at  various 
depths  beneath  it.  But,  in  pursuing  such  researches,  we  soon  find 
ourselves  led  on  to  consider  the  successive  changes  which  have  taken 
place  in  the  former  state  of  the  earth's  surface  and  interior,  and  the 
causes  which  have  given  rise  to  these  changes ;  and,  what  is  still 
more  singular  and  unexpected,  we  soon  become  engaged  in  researches 
into  the  history  of  the  animate  creation,  or  of  the  various  tribes  of 
animals  and  plants  which  have,  at  different  periods  of  the  past,  in- 
habited the  globe. 

All  are  aware  that  the  solid  parts  of  the  earth  consist  of  distinct 
substances,  such  as  clay,  chalk,  sand,  limestone,  coal,  slate,  granite, 
and  the  like ;  but  previously  to  observation  it  is  commonly  imagined 
that  all  these  had  remained  from  the  first  in  the  state  in  which  we 
now  see  them, —  that  they  were  created  in  their  present  form,  and  in 
their  present  position.  The  geologist  soon  comes  to  a  different  con- 
clusion, discovering  proofs  that  the  external  parts  of  the  earth  were 
not  all  produced  in  the  beginning  of  things  in  the  state  in  which  we 
now  behold  them,  nor  in  an  instant  of  time.  On  the  contrary,  he 
can  show  that  they  have  acquired  their  actual  configuration  and  con- 
dition gradually,  under  a  great  variety  of  circumstances,  and  at  suc- 
cessive periods,  during  each  of  which  distinct  races  of  living  beings 

B 


2  CLASSIFICATION    OF    ROCKS.  [Cn.  I. 

have  flourished  on  the  land  and  in  the  waters,  the  remains  of  these 
creatures  still  lying  buried  in  the  crust  of  the  earth. 

By  the  "  earth's  crust,"  is  meant  that  small  portion  of  the  exterior 
of  our  planet  which  is  accessible  to  human  observation,  or  on  which 
we  are  enabled  to  reason  by  observations  made  at  or  near  the  surface. 
These  reasonings  may  extend  to  a  depth  of  several  miles,  perhaps  ten 
miles;  and  even  then  it  may  be  said,  that  such  a  thickness  is  no 
more  than  ^-^  part  of  the  distance  from  the  surface  to  the  centre. 
The  remark  is  just;  but  although  the  dimensions  of  such  a  crust  are, 
in  truth,  insignificant  when  compared  to  the  entire  globe,  yet  they 
are  vast,  and  of  magnificent  extent  in  relation  to  man,  and  to  the  or- 
ganic beings  which  people  our  globe.  Referring  to  this  standard  of 
magnitude,  the  geologist  may  admire  the  ample  limits  of  his  domain, 
and  admit,  at  the  same  time,  that  not  only  the  exterior  of  the  planet, 
but  the  entire  earth,  is  but  an  atom  in  the  midst  of  the  countless 
worlds  surveyed  by  the  astronomer. 

The  materials  of  this  crust  are  not  thrown  together  confusedly ; 
but  distinct  mineral  masses,  called  rocks,  are  found  to  occupy  definite 
spaces,  and  to  exhibit  a  certain  order  of  arrangement.  The  term 
rock  is  applied  indifferently  by  geologists  to  all  these  substances, 
whether  they  be  soft  or  stony,  for  clay  and  sand  are  included  in  the 
term,  and  some  have  even  brought  peat  under  this  denomination. 
Our  older  writers  endeavoured  to  avoid  offering  such  violence  to  our 
language,  by  speaking  of  the  component  materials  of  the  earth  as 
consisting  of  rocks  and  soils.  But  there  is  often  so  insensible  a  pas- 
sage from  a  soft  and  incoherent  state  to  that  of  stone,  that  geologists 
of  all  countries  have  found  it  indispensable  to  have  one  technical 
term  to  include  both,  and  in  this  sense  we  find  roche  applied  in 
French,  rocca  in  Italian,  and  felsart  in  German.  The  beginner, 
however,  must  constantly  bear  in  mind,  that  the  term  rock  by  no 
means  implies  that  a  mineral  mass  is  in  an  indurated  or  stony  con- 
dition. 

The  most  natural  and  convenient  mode  of  classifying  the  various 
rocks  which  compose  the  earth's  crust,  is  to  refer,  in  the  first  place, 
to  their  origin,  and  in  the  second  to  their  relative  age.  I  shall 
therefore  begin  by  endeavouring  briefly  to  explain  to  the  student 
how  all  rocks  may  be  divided  into  four  great  classes  by  reference  to 
their  different  origin,  or,  in  other  words,  by  reference  to  the  different 
circumstances  and  causes  by  which  they  have  been  produced. 

The  first  two  divisions,  which  will  at  once  be  understood  as  natural, 
are  the  aqueous  and  volcanic,  or  the  products  of  watery  and  those  of 
igneous  action  at  or  near  the  surface. 

Aqueous  rocks. —  The  aqueous  rocks,  sometimes  called  the  sedi- 
mentary, or  fossiliferous,  cover  a  larger  part  of  the  earth's  surface 
than  any  others.  These  rocks  are  stratified,  or  divided  into  distinct 
layers,  or  strata.  The  term  stratum  means  simply  a  bed,  or  any 
thing  spread  out  or  strewed  over  a  given  surface  ;  and  we  infer  that 
these  strata  have  been  generally  spread  out  by  the  action  of  water, 
from  what  we  daily  see  taking  place  near  the  mouths  of  rivers,  or  on 


CH.  I.]  AQUEOUS   ROCKS.  3 

the  land  during  temporary  inundations.  For,  whenever  a  running 
stream  charged  with  mud  or  sand,  has  its  velocity  checked,  as  when 
it  enters  a  lake  or  sea,  or  overflows  a  plain,  the  sediment,  previously 
held  in  suspension  by  the  motion  of  the  water,  sinks,  by  its  own 
gravity,  to  the  bottom.  In  this  manner  layers  of  mud  and  sand  are 
thrown  down  one  upon  another. 

If  we  drain  a  lake  which  has  been  fed  by  a  small  stream,  we  fre- 
quently find  at  the  bottom  a  series  of  deposits,  disposed  with  consi- 
derable regularity,  one  above  the  other ;  the  uppermost,  perhaps,  may 
be  a  stratum  of  peat,  next  below  a  more  dense  and  solid  variety  of 
the  same  material ;  still  lower  a  bed  of  shell-marl,  alternating  with 
peat  or  sand,  and  then  other  beds  of  marl,  divided  by  layers  of  clay. 
Now,  if  a  second  pit  be  sunk  through  the  same  continuous  lacustrine 
formation,  at  some  distance  from  the  first,  nearly  the  same  series  of 
beds  is  commonly  met  with,  yet  with  slight  variations ;  some,  for  ex- 
ample, of  the  layers  of  sand,  clay,  or  marl,  may  be  wanting,  one  or 
more  of  them  having  thinned  out  and  given  place  to  others,  or  some- 
times one  of  the  masses  first  examined  is  observed  to  increase  in 
thickness  to  the  exclusion  of  other  beds. 

The  term  "formation"  which  I  have  used  in  the  above  explana- 
tion, expresses  in  geology  any  assemblage  of  rocks  which  have  some 
character  in  common,  whether  of  origin,  age,  or  composition.  Thus 
we  speak  of  stratified  and  unstratified,  freshwater  and  marine,  aqueous 
and  volcanic,  ancient  and  modern,  metalliferous  and  non-metallifer- 
ous formations. 

In  the  estuaries  of  large  rivers,  such  as  the  Ganges  and  the  Missis- 
sippi, we  may  observe,  at  low  water,  phenomena  analogous  to  those 
of  the  drained  lakes  above  mentioned,  but  on  a  grander  scale,  and 
extending  over  areas  several  hundred  miles  in  length  and  breadth. 
When  the  periodical  inundations  subside,  the  river  hollows  out  a 
channel  to  the  depth  of  many  yards  through  horizontal  beds  of  clay 
and  sand,  the  ends  of  which  are  seen  exposed  in  perpendicular  cliffs. 
These  beds  vary  in  their  mineral  composition,  or  colour,  or  in  the 
fineness  or  coarseness  of  their  particles,  and  some  of  them  are  occa- 
sionally characterized  by  containing  drift  wood.  At  the  junction  of 
the  river  and  the  sea.  especially  in  lagoons  nearly  separated  by  sand 
bars  from  the  ocean,  deposits  are  often  formed  in  which  brackish- 
water  and  salt-water  shells  are  included. 

The  annual  floods  of  the  Nile  in  Egypt  are  well  known,  and  the 
fertile  deposits  of  mud  which  they  leave  on  the  plains.  This  mud  is 
stratified,  the  thin  layer  thrown  down  in  one  season  differing  slightly 
in  colour  from  that  of  a  previous  year,  and  being  separable  from  it, 
as  has  been  observed  in  excavations  at  Cairo,  and  other  places.* 

When  beds  of  sand,  clay,  and  marl,  containing  shells  and  vegetable 
matter,  are  found  arranged  in  a  similar  manner  in  the  interior  of  the 
earth,  we  ascribe  to  them  a  similar  origin  ;  and  the  more  we  examine 
their  characters  in  minute  detail,  the  more  exact  do  we  find  the  re- 
semblance. Thus,  for  example,  at  various  heights  and  depths  in  the 

*  See  Principles  of  Geology,  by  the  Author,  Index,  "  Nile,"  « Rivers,"  &c. 

B  2 


4  AQUEOUS   KOCKS.  [Cli.  I. 

earth,  and  often  far  from  seas,  lakes,  and  rivers,  we  meet  with  layers 
of  rounded  pebbles  composed  of  flint,  limestone,  granite,  or  other  rocks, 
resembling  the  shingles  of  a  sea-beach  or  the  gravel  in  a  torrent's  bed. 
Such  layers  of  pebbles  frequently  alternate  with  others  formed 
of  sand  or  fine  sediment,  just  as  we  may  see  in  the  channel  of  a  river 
descending  from  hills  bordering  a  coast,  where  the  current  sweeps 
down  at  one  season  coarse  sand  and  gravel,  while  at  another,  when 
the  waters  are  low  and  less  rapid,  fine  mud  and  sand  alone  are 
carried  seaward.* 

If  a  stratified  arrangement,  and  the  rounded  form  of  pebbles,  are 
alone  sufficient  to  lead  us  to  the  conclusion  that  certain  rocks  origi- 
nated under  water,  this  opinion  is  farther  confirmed  by  the  distinct 
and  independent  evidence  of  fossils,  so  abundantly  included  in  the 
earth's  crust.  By  a  fossil  is  meant  any  body,  or  the  traces  of  the 
existence  of  any  body,  whether  animal  or  vegetable,  which  has  been 
buried  in  the  earth  by  natural  causes.  Now  the  remains  of  animals, 
especially  of  aquatic  species,  are  found  almost  everywhere  imbedded, 
in  stratified  rocks,  and  sometimes,  in  the  case  of  limestone,  they  are 
in  such  abundance  as  to  constitute  the  entire  mass  of  the  rock  itself. 
Shells  and  corals  are  the  most  frequent,  and  with  them  are  often 
associated  the  bones  and  teeth  of  fishes,  fragments  of  wood,  im- 
pressions of  leaves,  and  other  organic  substances.  Fossil  shells,  of 
forms  such  as  now  abound  in  the  sea,  are  met  with  far  inland,  both 
near  the  surface,  and  at  great  depths  below  it.  They  occur  at  all 
heights  above  the  level  of  the  ocean,  having  been  observed  at  eleva- 
tions of  more  than  8000  feet  in  the  Pyrenees,  10,000  in  the  Alps, 
13,000  in  the  Andes,  and  above  18,000  feet  in  the  Himalaya.f 

These  shells  belong  mostly  to  marine  testacea,  but  in  some  places 
exclusively  to  forms  characteristic  of  lakes  and  rivers.  Hence  it  is 
concluded  that  some  ancient  strata  were  deposited  at  the  bottom  of 
the  sea,  and  others  in  lakes  and  estuaries. 

When  geology  was  first  cultivated,  it  was  a  general  belief,  that 
these  marine  shells  and  other  fossils  were  the  effects  and  proofs  of 
the  deluge  of  Noah ;  but  all  who  have  carefully  investigated  the 
phenomena  have  long  rejected  this  doctrine.  A  transient  flood 
might  be  supposed  to  leave  behind  it,  here  and  there  upon  the  surface, 
scattered  heaps  of  mud,  sand,  and  shingle,  with  shells  confusedly  in- 
termixed ;  but  the  strata  containing  fossils  are  not  superficial  depo- 
sits, and  do  not  simply  cover  the  earth,  but  constitute  the  entire  mass 
of  mountains.  Nor  are  the  fossils  mingled  without  reference  to  the 
original  habits  and  natures  of  the  creatures  of  which  they  are  the 
memorials  ;  those,  for  example,  being  found  associated  together  which 
lived  in  deep  or  in  shallow  water,  near  the  shore  or  far  from  it,  in 
brackish  or  in  salt  water. 

It  has,  moreover,  been  a  favourite  notion  of  some  modern  writers, 
who  were  aware  that  fossil  bodies  could  not  all  be  referred  to  the 
deluge,  that  they,  and  the  strata  in  which  they  are  entombed,  might 

*  See  p.  18.  fig.  7. 

t  Capt.  R.  J.  Strachey  found  oolitic  fossils  18,400  feet  high  in  the  Himalaya. 


On.  I.]  VOLCANIC   ROCKS.  5 

have  been  deposited  in  the  bed  of  the  ocean  during  the  period  which 
intervened  between  the  creation  of  man  and  the  deluge.  They  have 
imagined  that  the  antediluvian  bed  of  the  ocean,  after  having  been 
the  receptacle  of  many  stratified  deposits,  became  converted,  at  the 
time  of  the  flood,  into  the  lands  which  we  inhabit,  and  that  the 
ancient  continents  were  at  the  same  time  submerged,  and  became  the 
bed  of  the  present  seas.  This  hypothesis,  although  preferable  to  the 
diluvial  theory  before  alluded  to,  since  it  admits  that  all  fossiliferous 
strata  were  successively  thrown  down  from  water,  is  yet  wholly 
inadequate  to  explain  the  repeated  revolutions  which  the  earth  has 
undergone,  and  the  signs  which  the  existing  continents  exhibit,  in 
most  regions,  of  having  emerged  from  the  ocean  at  an  era  far  more 
remote  than  four  thousand  years  from  the  present  time.  Ample 
proofs  of  these  reiterated  revolutions  will  be  given  in  the  sequel,  and 
it  will  be  seen  that  many  distinct  sets  of  sedimentary  strata,  hundreds 
and  sometimes  thousands  of  feet  thick,  are  piled  one  upon  the  other 
in  the  earth's  crust,  each  containing  peculiar  fossil  animals  and  plants 
of  species  distinguishable  for  the  most  part  from  all  those  now 
living.  The  mass  of  some  of  these  strata  consists  almost  entirely  of 
corals,  others  are  made  up  of  shells,  others  of  plants  turned  into  coal, 
while  some  are  without  fossils.  In  one  set  of  strata  the  species  of 
fossils  are  marine;  in  another,  lying  immediately  above  or  below, 
they  as  clearly  prove  that  the  deposit  was  formed  in  a  lake  or  in  a 
brackish  estuary.  When  the  student  has  more  fully  examined  into 
these  appearances,  he  will  become  convinced  that  the  time  required 
for  the  origin  of  the  rocks  composing  the  actual  continents  must 
have  been  far  greater  than  that  which  is  conceded  by  the  theory 
above  alluded  to ;  and  likewise  that  no  "one  universal  or  sudden 
conversion  of  sea  into  land  will  account  for  geological  appearances. 

We  have  now  pointed  out  one  great  class  of  rocks,  which,  however 
they  may  vary  in  mineral  composition,  colour,  grain,  or  other  cha- 
racters, external  and  internal,  may  nevertheless  be  grouped  together 
as  having  a  common  origin.  They  have  all  been  formed  under  water, 
in  the  same  manner  as  modern  accumulations  of  sand,  mud,  shingle, 
banks  of  shells,  reefs  of  coral,  and  the  like,  and  are  all  characterised 
by  stratification  or  fossils,  or  by  both. 

Volcanic  rocks.  —  The  division  of  rocks  which  we  may  next  con- 
sider are  the  volcanic,  or  those  which  have  been  produced  at  or  near 
the  surface  whether  in  ancient  or  modern  times,  not  by  water,  but  by 
the  action  of  fire  or  subterranean  heat.  These  rocks  are  for  the 
most  part  unstratified,  and  are  devoid  of  fossils.  They  are  more  par- 
tially distributed  than  aqueous  formations,  at  least  in  respect  to  hori- 
zontal extension.  Among  those  parts  of  Europe  where  they  exhibit 
characters  not  to  be  mistaken,  I  may  mention  not  only  Sicily  and  the 
country  round  Naples,  but  Auvergne,  Yelay,  and  Vivarais,  now  the 
departments  of  Puy  de  Dome,  Haute  Loire,  and  Ardeche,  towards 
the  centre  and  south  of  France,  in  which  are  several  hundred  conical 
hills  having  the  forms  of  modern  volcanos,  with  craters  more  or  less 
perfect  on  many  of  their  summits.  These  cones  are  composed  more- 

B  3 


6  VOLCANIC   ROCKS.  [Cfl.  I. 

over  of  lava,  sand,  and  ashes,  similar  to  those  of  active  volcanos. 
Streams  of  lava  may  sometimes  be  traced  from  the  cones  into  the 
adjoining  valleys,  where  they  have  choked  up  the  ancient  channels  of 
rivers  with  solid  rock,  in  the  same  manner  as  some  modern  flows  of 
lava  in  Iceland  have  been  known  to  do,  the  rivers  either  flowing 
beneath  or  cutting  out  a  narrow  passage  on  one  side  of  the  lava. 
Although  none  of  these  French  volcanos  have  been  in  activity  within 
the  period  of  history  or  tradition,  their  forms  are  often  very  perfect. 
Some,  however,  have  been  compared  to  the  mere  skeletons  of  vol- 
canos, the  rains  and  torrents  having  washed  their  sides,  and  removed 
all  the  loose  sand  and  scoriae,  leaving  only  the  harder  and  more  solid 
materials.  By  this  erosion,  and  by  earthquakes,  their  internal  struc- 
ture has  occasionally  been  laid  open  to  view,  in  fissures  and  ravines ; 
and  we  then  behold  not  only  many  successive  beds  and  masses  of 
porous  lava,  sand,  and  scoriae,  but  also  perpendicular  walls,  or  dikes, 
as  they  are  called,  of  volcanic  rock,  which  have  burst  through  the 
other  materials.  Such  dikes  are  also  observed  in  the  structure  of 
Vesuvius,  Etna,  and  other  active  volcanos.  They  have  been  formed 
by  the  pouring  of  melted  matter,  whether  from  above  or  below,  into 
open  fissures,  and  they  commonly  traverse  deposits  of  volcanic  tuff, 
a  substance  produced  by  the  showering  down  from  the  air,  or  in- 
cumbent waters,  of  sand  and  cinders,  first  shot  up  from  the  interior 
of  the  earth  by  the  explosions  of  volcanic  gases. 

Besides  the  parts  of  France  above  alluded  to,  there  are  other 
countries,  as  the  north  of  Spain,  the  south  of  Sicily,  the  Tuscan 
territory  of  Italy,  the  lower  Rhenish  provinces,  and  Hungary,  where 
spent  volcanos  may  be  seen,  still  preserving  in  many  cases  a  conical 
form,  and  having  craters  and  often  lava-streams  connected  with  them. 

There  are  also  other  rocks  in  England,  Scotland,  Ireland,  and 
almost  every  country  in  Europe,  which  we  infer  to  be  of  igneous 
origin,  although  they  do  not  form  hills  with  cones  and  craters.  Thus, 
for  example,  we  feel  assured  that  the  rock  of  Staffa,  and  that  of  the 
Giant's  Causeway,  called  basalt,  is  volcanic,  because  it  agrees  in  its 
columnar  structure  and  mineral  composition  with  streams  of  lava 
which  we  know  to  have  flowed  from  the  craters  of  volcanos.  We 
find  also  similar  basaltic  and  other  igneous  rocks  associated  with 
beds  of  tuff  in  various  parts  of  the  British  Isles,  and  forming  dikes, 
such  as  have  been  spoken  of;  and  some  of  the  strata  through  which 
these  dikes  cut  are  occasionally  altered  at  the  point  of  contact,  as  if 
they  had  been  exposed  to  the  intense  heat  of  melted  matter. 

The  absence  of  cones  and  craters,  and  long  narrow  streams  of 
superficial  lava,  in  England  and  many  other  countries,  is  principally 
to  be  attributed  to  the  'eruptions  having  been  submarine,  just  as  a 
considerable  proportion  of  volcanos  in  our  own  times  burst  out 
beneath  the  sea.  But  this  question  must  be  enlarged  upon  more 
fully  in  the  chapters  on  Igneous  Rocks,  in  which  it  will  also  be 
shown,  that  as  different  sedimentary  formations,  containing  each 
their  characteristic  fossils,  have  been  deposited  at  successive  periods, 
so  also  volcanic  sand  and  scoriae  have  been  thrown  out,  and  lavas 


CH.  I.]  PLUTONIC   ROCKS.  7 

have  flowed  over  the  land  or  bed  of  the  sea,  at  many  different  epochs, 
or  have  been  injected  into  fissures ;  so  that  the  igneous  as  well  as 
the  aqueous  rocks  may  be  classed  as  a  chronological  series  of  monu- 
ments, throwing  light  on  a  succession  of  events  in  the  history  of  the 
earth. 

Plutonic  rocks  (Granite,  &c.).  —  We  have  now  pointed  out  the 
existence  of  two  distinct  orders  of  mineral  masses,  the  aqueous  and 
the  volcanic:  but  if  we  examine  a  large  portion  of  a  continent, 
especially  if  it  contain  within  it  a  lofty  mountain  range,  we  rarely  fail 
to  discover  two  other  classes  of  rocks,  very  distinct  from  either  of 
those  above  alluded  to,  and  which  we  can  neither  assimilate  to  de- 
posits such  as  are  now  accumulated  in  lakes  or  seas,  nor  to  those 
generated  by  ordinary  volcanic  action.  The  members  of  both  these 
divisions  of  rocks  agree  in  being  highly  crystalline  and  destitute  of 
organic  remains.  The  rocks  of  one  division  have  been  called  plu- 
tonic,  comprehending  all  the  granites  and  certain  porphyries,  which 
are  nearly  allied  in  some  of  their  characters  to  volcanic  formations. 
The  members  of  the  other  class  are  stratified  and  often  slaty,  and 
have  been  called  by  some  the  crystalline  schists,  in  which  group  are 
included  gneiss,  micaceous-schist  (or  mica-slate),  hornblende-schist, 
statuary  marble,  the  finer  kinds  of  roofing  slate,  and  other  rocks 
afterwards  to  be  described. 

As  it  is  admitted  that  nothing  strictly  analogous  to  these  crystalline 
productions  can  now  be  seen  in  the  progress  of  formation  on  the 
earth's  surface,  it  will  naturally  be  asked,  on  what  data  we  can  find 
a  place  for  them  in  a  system  of  classification  founded  on  the  origin  of 
rocks.  I  cannot,  in  reply  to  this  question,  pretend  to  give  the 
student,  in  a  few  words,  an  intelligible  account  of  the  long  chain  of 
facts  and  reasonings  by  which  geologists  have  been  led  to  infer  the 
analogy  of  the  rocks  in  question  to  others  now  in  progress  at  the 
surface.  The  result,  however,  may  be  briefly  stated.  All  the  various 
kinds  of  granite  which  constitute  the  plutonic  family,  are  supposed 
to  be  of  igneous  origin,  but  to  have  been  formed  under  great  pressure, 
at  a  considerable  depth  in  the  earth,  or  sometimes,  perhaps,  under  a 
certain  weight  of  incumbent  water.  Like  the  lava  of  volcanos,  they 
have  been  melted,  and  have  afterwards  cooled  and  crystallised,  but 
with  extreme  slowness,  and  under  conditions  very  different  from 
those  of  bodies  cooling  in  the  open  air.  Hence  they  differ  from  the 
volcanic  rocks,  not  only  by  their  more  crystalline  texture,  but  also 
by  the  absence  of  tuffs  and  breccias,  which  are  the  products  of 
eruptions  at  the  earth's  surface,  or  beneath  seas  of  inconsiderable 
depth.  They  differ  also  by  the  absence  of  pores  or  cellular  cavities, 
to  which  the  expansion  of  the  entangled  gases  gives  rise  in  ordinary 
lava. 

Although  granite  has  often  pierced  through  other  strata,  it  has 
rarely,  if  ever,  been  observed  to  rest  upon  them,  as  if  it  had  over- 
flowed. But  as  this  is  continually  the  case  with  the  volcanic  rocks, 
they  have  been  styled,  from  this  peculiarity,  "  overlying  "  by  Dr.  Mac 
Culloch;  and  Mr.  Necker  has  proposed  the  term  "  underlying "  for 

B  4 


8  METAMORPHIC    ROCKS.  [Cfl.  I. 

the  granites,  to  designate  the  opposite  mode  in  which  they  almost 
invariably  present  themselves. 

Metamorphic,  or  stratified  crystalline  rocks. — The  fourth  and  last 
great  division  of  rocks  are  the  crystalline  strata  and  slates,  or  schists, 
called  gneiss,  mica-schist,  clay-slate,  chlorite-schist,  marble,  and  the 
like,  the  origin  of  which  is  more  doubtful  than  that  of  the  other  three 
classes.  They  contain  no  pebbles,  or  sand,  or  scoriae,  or  angular 
pieces  of  imbedded  stone,  and  no  traces  of  organic  bodies,  and  they 
are  often  as  crystalline  as  granite,  yet  are  divided  into  beds,  corre- 
sponding in  form  and  arrangement  to  those  of  sedimentary  formations, 
and  are  therefore  said  to  be  stratified.  The  beds  sometimes  consist 
of  an  alternation  of  substances  varying  in  colour,  composition,  and 
thickness,  precisely  as  we  see  in  stratified  fossiliferous  deposits.  Ac- 
cording to  the  Huttonian  theory,  which  I  adopt  as  the  most  probable, 
and  which  will  be  afterwards  more  fully  explained,  the  materials  of 
these  strata  were  originally  deposited  from  water  in  the  usual  form 
of  sediment,  but  they  were  subsequently  so  altered  by  subterranean 
heat,  as  to  assume  a  new  texture.  It  is  demonstrable,  in  some  cases 
at  least,  that  such  a  complete  conversion  has  actually  taken  place, 
fossiliferous  strata  having  exchanged  an  earthy  for  a  highly  crys- 
talline texture  for  a  distance  of  a  quarter  of  a  mile  from  their  contact 
with  granite.  In  some  cases,  dark  limestones,  replete  with  shells  and 
corals,  have  been  turned  into  white  statuary  marble,  and  hard  clays, 
containing  vegetable  or  other  remains,  into  slates  called  mica-schist 
or  hornblende-schist,  every  vestige  of  the  organic  bodies  having  been 
obliterated. 

Although  we  are  in  a  great  degree  ignorant  of  the  precise  nature 
of  the  influence  exerted  in  these  cases,  yet  it  evidently  bears  some 
analogy  to  that  which  volcanic  heat  and  gases  are  known  to  pro- 
duce ;  and  the  action  may  be  conveniently  called  plutonic,  because  it 
appears  to  have  been  developed  in  those  regions  where  plutonic 
rocks  are  generated,  and  under  similar  circumstances  of  pressure  and 
depth  in  the  earth.  Whether  hot  water  or  steam  permeating  stratified 
masses,  or  electricity,  or  any  other  causes  have  co-operated  to  produce 
the  crystalline  texture,  may  be  matter  of  speculation,  but  it  is  clear 
that  the  plutonic  influence  has  sometimes  pervaded  entire  mountain 
masses  of  strata. 

In  accordance  with  the  hypothesis  above  alluded  to,  I  proposed  in 
the  first  edition  of  the  Principles  of  Geology  (1833),  the  term 
"Metamorphic"  for  the  altered  strata,  a  term  derived  from  /zera, 
meta,  trans,  and  poptyr),  morphe,  forma. 

Hence  there  are  four  great  classes  of  rocks  considered  in  reference 
to  their  origin, — the  aqueous,  the  volcanic,  the  plutonic,  and  the 
metamorphic.  In  the  course  of  this  work  it  will  be  shown,  that 
portions  of  each  of  these  four  distinct  classes  have  originated  at 
many  successive  periods.  They  have  all  been  produced  contem- 
poraneously, and  may  even  now  be  in  the  progress  of  formation  on  a 
large  scale.  It  is  not  true,  as  was  formerly  supposed,  that  all  granites, 
together  with  the  crystalline  or  metamorphic  strata,  were  first  formed, 


CH.  I.]      FOUR  GLASSES  OF   ROCKS  CONTEMPORANEOUS.  9 

and  therefore  entitled  to  be  called  "  primitive,"  and  that  the  aqueous 
and  volcanic  rocks  were  afterwards  super-imposed,  and  should,  there- 
fore, rank  as  secondary  in  the  order  of  time.  This  idea  was  adopted 
in  the  infancy  of  the  science,  when  all  formations,  whether  stratified 
or  unstratified,  earthy  or  crystalline,  with  or  without  fossils,  were 
alike  regarded  as  of  aqueous  origin.  At  that  period  it  was  naturally 
argued,  that  the  foundation  must  be  older  than  the  superstructure ; 
but  it  was  afterwards  discovered,  that  this  opinion  was  by  no  means 
in  every  instance  a  legitimate  deduction  from  facts ;  for  the  inferior 
parts  of  the  earth's  crust  have  often  been  modified,  and  even  entirely 
changed,  by  the  influence  of  volcanic  and  other  subterranean  causes, 
while  super-imposed  formations  have  not  been  in  the  slightest  degree 
altered.  In  other  words,  the  destroying  and  renovating  processes 
have  given  birth  to  new  rocks  below,  while  those  above,  whether 
crystalline  or  fossiliferous,  have  remained  in  their  ancient  condition. 
Even  in  cities,  such  as  Venice  and  Amsterdam,  it  cannot  be  laid 
down  as  universally  true,  that  the  upper  parts  of  each  edifice,  whether 
of  brick  or  marble,  are  more  modern  than  the  foundations  on  which 
they  rest,  for  these  often  consist  of  wooden  piles,  which  may  have 
rotted  and  been  replaced  one  after  the  other,  without  the  least  injury 
to  the  buildings  above  ;  meanwhile,  these  may  have  required  scarcely 
any  repair,  and  may  have  been  constantly  inhabited.  So  it  is  with  the 
habitable  surface  of  our  globe,  in  its  relation  to  large  masses  of  rock 
immediately  below :  it  may  continue  the  same  for  ages,  while  sub- 
jacent materials,  at  a  great  depth,  are  passing  from  a  solid  to  a  fluid 
state,  and  then  reconsolidating,  so  as  to  acquire  a  new  texture. 

As  all  the  crystalline  rocks  may,  in  some  respects,  be  viewed  as 
belonging  to  one  great  family,  whether  -they  be  stratified  or  un- 
stratified, plutonic  or  metamorphic,  it  will  often  be  convenient  to 
speak  of  them  by  one  common  name.  It  being  now  ascertained,  as 
above  stated,  that  they  are  of  very  different  ages,  sometimes  newer 
than  the  strata  called  secondary,  the  terms  primitive  and  primary 
which  were  formerly  used  for  the  whole  must  be  abandoned,  as  they 
would  imply  a  manifest  contradiction.  It  is  indispensable,  therefore, 
to  find  a  new  name,  one  which  must  not  be  of  chronological  import, 
and  must  express,  on  the  one  hand,  some  peculiarity  equally  attribu- 
table to  granite  and  gneiss  (to  the  plutonic  as  well  as  the  altered 
rocks),  and,  on  the  other,  must  have  reference  to  characters  in  which 
those  rocks  differ,  both  from  the  volcanic  and  from  the  unaltered 
sedimentary  strata.  I  proposed  in  the  Principles  of  Geology  (first 
edition,  vol.  iii.),  the  term  "hypogene"  for  this  purpose,  derived  from 
VTTO,  under,  and  yivo/uat,  to  be,  or  to  be  born  ;  a  word  implying  the 
theory  that  granite,  gneiss,  and  the  other  crystalline  formations  are 
alike  netherformed  rocks,  or  rocks  which  have  not  assumed  their 
present  form  and  structure  at  the  surface.  They  occupy  the  lowest 
place  in  the  order  of  superposition.  Even  in  regions  such  as  the  Alps, 
where  some  masses  of  granite  and  gneiss  can  be  shown  .to  be  of  com- 
paratively modern  date,  belonging,  for  example,  to  the  period  here- 
after to  be  described  as  tertiary,  they  are  still  underlying  rocks. 


10  COMPONENTS   OF   STRATA.  [Cn.  IT. 

They  never  repose  on  the  volcanic  or  trappean  formations,  nor  on 
strata  containing  organic  remains.  They  are  hypogene,  as  "  being 
under  "  all  the  rest. 

From  what  has  now  been  said,  the  reader  will  understand  that 
each  of  the  four  great  classes  of  rocks  may  be  studied  under  two 
distinct  points  of  view ;  first,  they  may  be  studied  simply  as  mineral 
masses  deriving  their  origin  from  particular  causes,  and  having  a 
certain  composition,  form,  and  position  in  the  earth's  crust,  or  other 
characters  both  positive  and  negative,  such  as  the  presence  or  absence 
of  organic  remains.  In  the  second  place,  the  rocks  of  each  class  may 
be  viewed  as  a  grand  chronological  series  of  monuments,  attesting  a 
succession  of  events  in  the  former  history  of  the  globe  and  its  living 
inhabitants. 

I  shall  accordingly  proceed  to  treat  of  each  family  of  rocks ;  first, 
in  reference  to  those  characters  which  are  not  chronological,  and  then 
in  particular  relation  to  the  several  periods  when  they  were  formed. 


CHAPTER  II. 

AQUEOUS   ROCKS  —  THEIR   COMPOSITION   AND   FORMS   OF    STRATIFI- 
CATION. 

Mineral  composition  of  strata — Arenaceous  rocks  —  Argillaceous — Calcareous — 
Gypsum  —  Forms  of  stratification  —  Original  horizontally  —  Thinning  out — Dia- 
gonal arrangement  —  Eipple  mark. 

IN  pursuance  of  the  arrangement  explained  in  the  last  chapter,  we 
shall  begin  by  examining  the  aqueous  or  sedimentary  rocks,  which 
are  for  the  most  part  distinctly  stratified,  and  contain  fossils.  We 
may  first  study  them  with  reference  to  their  mineral  composition, 
external  appearance,  position,  mode  of  origin,  organic  contents,  and 
other  characters  which  belong  to  them  as  aqueous  formations,  inde- 
pendently of  their  age,  and  we  may  afterwards  consider  them  chrono- 
logically or  with  reference  to  the  successive  geological  periods  when 
they  originated. 

I  have  already  given  an  outline  of  the  data  which  led  to  the  belief 
that  the  stratified  and  fossiliferous  rocks  were  originally  deposited 
under  water ;  but,  before  entering  into  a  more  detailed  investigation, 
it  will  be  desirable  to  say  something  of  the  ordinary  materials  of  which 
such  strata  are  composed.  These  may  be  said  to  belong  principally 
to  three  divisions,  the  arenaceous,  the  argillaceous,  and  the  calca- 
reous, which  are  formed  respectively  of  sand,  clay,  and  carbonate  of 
lime.  Of  these,  the  arenaceous,  or  sandy  masses,  are  chiefly  made 
up  of  siliceous  or  flinty  grains ;  the  argillaceous,  or  clayey,  of  a 
mixture  of  siliceous  matter,  with  a  certain  proportion,  about  a  fourth 
in  weight,  of  aluminous  earth ;  and,  lastly,  the  calcareous  rocks  or 
limestones  consist  of  carbonic  acid  and  lime. 


CH.  II.]     MINERAL   COMPOSITION   OF    STRATIFIED   ROCKS.       11 

Arenaceous  or  siliceous  rocks.  —  To  speak  first  of  the  sandy  divi- 
sion :  beds  of  loose  sand  are  frequently  met  with,  of  which  the  grains 
consist  entirely  of  silex,  which  term  comprehends  all  purely  siliceous 
minerals,  as  quartz  and  common  flint.  Quartz  is  silex  in  its  purest 
form.  Flint  usually  contains  some  admixture  of  alumine  and  oxide  of 
iron.  The  siliceous  grains  in  sand  are  usually  rounded,  as  if  by  the 
action  of  running  water.  Sandstone  is  an  aggregate  of  such  grains, 
which  often  cohere  together  without  any  visible  cement,  but  more 
commonly  are  bound  together  by  a  slight  quantity  of  siliceous  or 
calcareous  matter,  or  by  iron  or  clay. 

Pure  siliceous  rocks  may  be  known  by  not  effervescing  when  a 
drop  of  nitric,  sulphuric  or  other  acid  is  applied  to  them,  or  by  the 
grains  not  being  readily  scratched  or  broken  by  ordinary  pressure. 
In  nature  there  is  every  intermediate  gradation,  from  perfectly  loose 
sand,  to  the  hardest  sandstone.  In  micaceous  sandstones  mica  is 
very  abundant ;  and  the  thin  silvery  plates  into  which  that  mineral 
divides,  are  often  arranged  in  layers  parallel  to  the  planes  of  strati- 
fication, giving  a  slaty  or  laminated  texture  to  the  rock. 

When  sandstone  is  coarse-grained,  it  is  usually  called  grit.  If  the 
grains  are  rounded,  and  large  enough  to  be  called  pebbles,  it  becomes 
a  conglomerate  or  pudding-stone,  which  may  consist  of  pieces  of  one 
or  of  many  different  kinds  of  rock.  A  conglomerate,  therefore,  is 
simply  gravel  bound  together  by  a  cement. 

Argillaceous  rocks.  — Clay,  strictly  speaking,  is  a  mixture  of  silex 
or  flint  with  a  large  proportion,  usually  about  one  fourth,  of  alumine, 
or  argil ;  but  in  common  language,  any  earth  which  possesses  suffi- 
cient ductility,  when  kneaded  up  with  water,  to  be  fashioned  like 
paste  by  the  hand,  or  by  the  potter's  lathe^is  called  a  clay;  and  such 
clays  vary  greatly  in  their  composition,  and  are,  in  general,  nothing 
more  than  mud  derived  from  the  decomposition  or  wearing  down  of 
rocks.  The  purest  clay  found  in  nature  is  porcelain  clay,  or  kaolin, 
which  results  from  the  decomposition  of  a  rock  composed  of  felspar 
and  quartz,  and  it  is  almost  always  mixed  with  quartz.*  Shale  has 
also  the  property,  like  clay,  of  becoming  plastic  in  water:  it  is  a  more 
solid  form  of  clay,  or  argillaceous  matter,  condensed  by  pressure.  It 
usually  divides  into  laminae  more  or  less  regular. 

One  general  character  of  all  argillaceous  rocks  is  to  give  out  a 
peculiar,  earthy  odour  when  breathed  upon,  which  is  a  test  of  the 
presence  of  alumine,  although  it  does  not  belong  to  pure  alumine, 
but,  apparently,  to  the  combination  of  that  substance  with  oxide  of 
iron.  | 

Calcareous  rocks.  — This  division  comprehends  those  rocks  which, 
like  chalk,  are  composed  chiefly  of  lime  and  carbonic  acid.  Shells 
and  corals  are  also  formed  of  the  same  elements,  with  the  addition 

*  The  kaolin  of  China  consists  of  71-15  nearly  equal  parts  of  silica  and  alumine, 

parts  of  silex,  15'86  of  alumine,  P92  of  with  1   per  cent,  of  magnesia.     (Phil, 

lime,   and   6'73  of  water  (W.  Phillips,  Mag.  vol.  x.  1837.) 
Mineralogy,  p.  33.);  but  other  porcelain        f  See  W.  Phillips's  Mineralogy,  "  Alu- 

clays  differ  materially,  that  of  Cornwall  mine." 
being  composed,  according  to  Boase,  of 


12      MINERAL   COMPOSITION   OF    STRATIFIED   ROCKS.      [Cn.  IT. 

of  animal  matter.  To  obtain  pure  lime  it  is  necessary  to  calcine 
these  calcareous  substances,  that  is  to  say,  to  expose  them  to  heat  of 
sufficient  intensity  to  drive  off  the  carbonic  acid,  and  other  volatile 
matter.  White  chalk  is  sometimes  pure  carbonate  of  lime  ;  and  this 
rock,  although  usually  in  a  soft  and  earthy  state,  is  occasionally 
sufficiently  solid  to  be  used  for  building,  and  even  passes  into  a 
compact  stone,  or  a  stone  of  which  the  separate  parts  are  so  minute 
as  not  to  be  distinguishable  from  each  other  by  the  naked  eye. 

Many  limestones  are  made  up  entirely  of  minute  fragments  of 
shells  and  coral,  or  of  calcareous  sand  cemented  together.  These 
last  might  be  called  "  calcareous  sandstones  ; "  but  that  term  is  more 
properly  applied  to  a  rock  in  which  the  grains  are  partly  calcareous 
and  partly  siliceous,  or  to  quartzose  sandstones,  having  a  cement  of 
carbonate  of  lime. 

The  variety  of  limestone  called  "  oolite  "  is  composed  of  numerous 
small  egg-like  grains,  resembling  the  roe  of  a  fish,  each  of  which  has 
usually  a  small  fragment  of  sand  as  a  nucleus,  around  which  con- 
centric layers  of  calcareous  matter  have  accumulated. 

Any  limestone  which  is  sufficiently  hard  to  take  a  fine  polish  is 
called  marble.  Many  of  these  are  fossiliferous ;  but  statuary  marble, 
which  is  also  called  saccharine  limestone,  as  having  a  texture  re- 
sembling that  of  loaf-sugar,  is  devoid  of  fossils,  and  is  in  many  cases 
a  member  of  the  metamorphic  series. 

Siliceous  limestone  is  an  intimate  mixture  of  carbonate  of  lime  and 
flint,  and  is  harder  in  proportion  as  the  flinty  matter  predominates. 

The  presence  of  carbonate  of  lime  in  a  rock  may  be  ascertained 
by  applying  to  the  surface  a  small  drop  of  diluted  sulphuric,  nitric, 
or  muriatic  acids,  or  strong  vinegar ;  for  the  lime,  having  a  greater 
chemical  affinity  for  any  one  of  these  acids  than  for  the  carbonic, 
unites  immediately  with  them  to  form  new  compounds,  thereby  be- 
coming a  sulphate,  nitrate,  or  muriate  of  lime.  The  carbonic  acid, 
when  thus  liberated  from  its  union  with  the  lime,  escapes  in  a  gaseous 
form,  and  froths  up  or  effervesces  as  it  makes  its  way  in  small  bubbles 
through  the  drop  of  liquid.  This  effervescence  is  brisk  or  feeble  in 
proportion  as  the  limestone  is  pure  or  impure,  or,  in  other  words, 
according  to  the  quantity  of  foreign  matter  mixed  with  the  carbonate 
of  lime.  Without  the  aid  of  this  test,  the  most  experienced  eye 
cannot  always  detect  the  presence  of  carbonate  of  lime  in  rocks. 

The  above-mentioned  three  classes  of  rocks,  the  siliceous,  argil- 
laceous, and  calcareous,  pass  continually  into  each  other,  and  rarely 
occur  in  a  perfectly  separate  and  pure  form.  Thus  it  is  an  exception 
to  the  general  rule  to  meet  with  a  limestone  as  pure  as  ordinary 
white  chalk,  or  with  clay  as  aluminous  as  that  used  in  Cornwall  for 
porcelain,  or  with  sand  so  entirely  composed  of  siliceous  grains  as  the 
white  sand  of  Alum  Bay  in  the  Isle  of  Wight,  or  sandstone  so  pure 
as  the  grit  of  Fontainebleau,  used  for  pavement  in  France.  More 
commonly  we  find  sand  and  clay,  or  clay  and  marl,  intermixed  in  the 
same  mass.  When  the  sand  and  clay  are  each  in  considerable 
quantity,  the  mixture  is  called  loam.  If  there  is  much  calcareous 


Cn.  II.]  FORMS   OF    STRATIFICATION.  13 

matter  in  clay  it  is  called  marl;  but  this  term  has  unfortunately  been 
used  so  vaguely,  as  often  to  be  very  ambiguous.  It  has  been  applied 
to  substances  in  which  there  is  no  lime ;  as,  to  that  red  loam  usually 
called  red  marl  in  certain  parts  of  England.  Agriculturists  were 
in  the  habit  of  calling  any  soil  a  marl,  which,  like  true  marl,  fell  to 
pieces  readily  on  exposure  to  the  air.  Hence  arose  the  confusion  of 
using  this  name  for  soils  which,  consisting  of  loam,  were  easily 
worked  by  the  plough,  though  devoid  of  lime. 

Marl  slate  bears  the  same  relation  to  marl  which  shale  bears  to 
clay,  being  a  calcareous  shale.  It  is  very  abundant  in  some  countries, 
as  in  the  Swiss  Alps.  Argillaceous  or  marly  limestone  is  also  of 
common  occurrence. 

There  are  few  other  kinds  of  rock  which  enter  so  largely  into  the 
composition  of  sedimentary  strata  as  to  make  it  necessary  to  dwell 
here  on  their  characters.  I  may,  however,  mention  two  others, — 
magnesian  limestone  or  dolomite,  and  gypsum.  Magnesian  limestone 
is  composed  of  carbonate  of  lime  and  carbonate  of  magnesia ;  the 
proportion  of  the  latter  amounting  in  some  cases  to  nearly  one  half. 
It  effervesces  much  more  slowly  and  feebly  with  acids  than  common 
limestone.  In  England  this  rock  is  generally  of  a  yellowish  colour ; 
but  it  varies  greatly  in  mineralogical  character,  passing  from  an 
earthy  state  to  a  white  compact  stone  of  great  hardness.  Dolomite, 
so  common  in  many  parts  of  Germany  and  France,  is  also  a  variety 
of  magnesian  limestone,  usually  of  a  granular  texture. 

Gypsum.  —  Gypsum  is  a  rock  composed  of  sulphuric  acid,  lime, 
and  water.  It  is  usually  a  soft  whitish-yellow  rock,  with  a  texture 
resembling  that  of  loaf-sugar,  but  sometimes  it  is  entirely  composed 
of  lenticular  crystals.  It  is  insoluble  in  acids,  and  does  not  effervesce 
like  chalk  and  dolomite,  because  it  does  not  contain  carbonic  acid 
gas,  or  fixed  air,  the  lime  being  already  combined  with  sulphuric 
acid,  for  which  it  has  a  stronger  affinity  than  for  any  other.  An- 
hydrous gypsum  is  a  rare  variety,  into  which  water  does  not  enter 
as  a  component  part.  Gypseous  marl  is  a  mixture  of  gypsum  and 
marl.  Alabaster  is  a  granular  and  compact  variety  of  gypsum  found 
in  masses  large  enough  to  be  used  in  sculpture  and  architecture.  It 
is  sometimes  a  pure  snow-white  substance,  as  that  of  Volterra  in 
Tuscany,  well  known  as  being  carved  for  works  of  art  in  Florence 
and  Leghorn.  It  is  a  softer  stone  than  marble,  and  more  easily 
wrought. 

Forms  of  stratification. — A  series  of  strata  sometimes  consists  of 
one  of  the  above  rocks,  sometimes  of  two  or  more  in  alternating  beds. 

Thus,  in  the  coal  districts  of  England,  for  example,  we  often  pass 
through  several  beds  of  sandstone,  some  of  finer,  others  of  coarser 
grain,  some  white,  others  of  a  dark  colour,  and  below  these,  layers 
of  shale  and  sandstone  or  beds  of  shale,  divisible  into  leaf-like  laminae, 
and  containing  beautiful  impressions  of  plants.  Then  again  we  meet 
with  beds  of  pure  and  impure  coal,  alternating  with  shales  and  sand- 
stones, and  underneath  the  whole,  perhaps,  are  calcareous  strata,  or 
beds  of  limestone,  filled  with  corals  and  marine  shells,  each  bed  dis- 


14  ALTERNATIONS.  [Cn.  II. 

tinguishable  from  another  by  certain  fossils,  or  by  the  abundance  of 
particular  species  of  shells  or  zoophytes. 

This  alternation  of  different  kinds  of  rock  produces  the  most  dis- 
tinct stratification ;  and  we  often  find  beds  of  limestone  and  marl, 
conglomerate  and  sandstone,  sand  and  clay,  recurring  again  and  again, 
in  nearly  regular  order,  throughout  a  series  of  many  hundred  strata. 
The  causes  which  may  produce  these  phenomena  are  various,  and 
have  been  fully  discussed  in  my  treatise  on  the  modern  changes  of 
the  earth's  surface.*  It  is  there  seen  that  rivers  flowing  into  lakes 
and  seas  are  charged  with  sediment,  varying  in  quantity,  composition, 
colour,  and  grain  according  to  the  seasons ;  the  waters  are  sometimes 
flooded  and  rapid,  at  other  periods  low  and  feeble ;  different  tribu- 
taries, also,  draining  peculiar  countries  and  soils,  and  therefore 
charged  with  peculiar  sediment,  are  swollen  at  distinct  periods.  It 
was  also  shown  that  the  waves  of  the  sea  and  currents  undermine  the 
cliffs  during  wintry  storms,  and  sweep  away  the  materials  into  the 
deep,  after  which  a  season  of  tranquillity  succeeds,  when  nothing  but 
the  finest  mud  is  spread  by  the  movements  of  the  ocean  over  the 
same  submarine  area. 

It  is  not  the  object  of  the  present  work  to  give  a  description  of 
these  operations,  repeated  as  they  are,  year  after  year,  and  century 
after  century ;  but  I  may  suggest  an  explanation  of  the  manner  in 
which  some  micaceous  sandstones  have  originated,  namely,  those  in 
which  we  see  innumerable  thin  layers  of  mica  dividing  layers  of  fine 
quartzose  sand.  I  observed  the  same  arrangement  of  materials  in 
recent  mud  deposited  in  the  estuary  of  La  Roche  St.  Bernard  in  Brit- 
tany, at  the  mouth  of  the  Loire.  The  surrounding  rocks  are  of  gneiss, 
which,  by  its  waste,  supplies  the  mud :  when  this  dries  at  low  water, 
it  is  found  to  consist  of  brown  laminated  clay,  divided  by  thin  seams 
of  mica.  The  separation  of  the  mica  in  this  case,  or  in  that  of  mica- 
ceous sandstones,  may  be  thus  understood  If  we  take  a  handful  of 
quartzose  sand,  mixed  with  mica,  and  throw  it  into  a  clear  running 
stream,  we  see  the  materials  immediately  sorted  by  the  water,  the 
grains  of  quartz  falling  almost  directly  to  the  bottom,  while  the  plates 
of  mica  take  a  much  longer  time  to  reach  the  bottom,  and  are  carried 
farther  down  the  stream.  At  the  first  instant  the  water  is  turbid,  but 
immediately  after  the  flat  surfaces  of  the  plates  of  mica  are  seen  all 
alone  reflecting  a  silvery  light,  as  they  descend  slowly,  to  form  a  dis- 
tinct micaceous  lamina.  The  mica  is  the  heavier  mineral  of  the  two ; 
but  it  remains  a  longer  time  suspended  in  the  fluid,  owing  to  its 
greater  extent  of  surface.  It  is  easy,  therefore,  to  perceive  that 
where  such  mud  is  acted  upon  by  a  river  or  tidal  current,  the  thin 
plates  of  mica  will  be  carried  farther,  and  not  deposited  in  the  same 
places  as  the  grains  of  quartz ;  and  since  the  force  and  velocity  of  the 
stream  varies  from  time  to  time,  layers  of  mica  or  of  sand  will  be 
thrown  down  successively  on  the  same  area. 

Original  horizontality. — It  is  said  generally  that  the  upper  and 

*  Consult  Index  to  Principles  of  Geology,  "  Stratification,"  "  Currents," 
«  Deltas,"  "  Water,"  &c. 


Cfl.  II.]  HORIZONTALS  Y   OF    STRATA.  15 

under  surfaces  of  strata,  or  the  "  planes  of  stratification,"  are  parallel. 
Although  this  is  not  strictly  true,  they  make  an  approach  to  parallelism, 
for  the  same  reason  that  sediment  is  usually  deposited  at  first  in  nearly 
horizontal  layers.  The  reason  of  this  arrangement  can  by  no  means 
be  attributed  to  an  original  evenness  or  horizontally  in  the  bed  of  the 
sea :  for  it  is  ascertained  that  in  those  places  where  no  matter  has  been 
recently  deposited,  the  bottom  of  the  ocean  is  often  as  uneven  as  that 
of  the  dry  land,  having  in  like  manner  its  hills,  valleys,  and  ravines. 
Yet  if  the  sea  should  sink,  or  the  water  be  removed  near  the  mouth 
of  a  large  river  where  a  delta  has  been  forming,  we  should  see 
extensive  plains  of  mud  and  sand  laid  dry,  which,  to  the  eye,  would 
appear  perfectly  level,  although,  in  reality,  they  would  slope  gently 
from  the  land  towards  the  sea. 

This  tendency  in  newly-formed  strata  to  assume  a  horizontal  posi- 
tion arises  principally  from  the  motion  of  the  water,  which  forces 
along  particles  of  sand  or  mud  at  the  bottom,  and  causes  them  to 
settle  in  hollows  or  depressions  where  they  are  less  exposed  to  the 
force  of  a  current  than  when  they  are  resting  on  elevated  points. 
The  velocity  of  the  current  and  the  motion  of  the  superficial  waves 
diminish  from  the  surface  downwards,  and  are  least  in  those  depres- 
sions where  the  water  is  deepest. 

A  good  illustration  of  the  principle  here  alluded  to  may  be 
sometimes  seen  in  the  neighbourhood  of  a  volcano,  when  a  section, 
whether  natural  or  artificial,  has  laid  open  to  view  a  succession  of 
various-coloured  layers  of  sand  and  ashes,  which  have  fallen  in 
showers  upon  uneven  ground.  Thus  let  A  B  (fig.  1.)  be  two  ridges, 
with  an  intervening  valley.  These  original  inequalities  of  the 
surface  have  been  gradually  effaced  by  beds  of  sand  and  ashes 
c,  d,  e,  the  surface  at  e  being  quite  level.  It  will  be  seen  that, 
although  the  materials  of  the  first  layers  have  accommodated  them- 
Fio,  ,  selves  in  a  great  degree  to  the  shape 

of  the  ground  A  B,  yet  each  bed  is 
thickest  at  the  bottom.  At  first  a 
great  many  particles  would  be  carried 
by  their  own  gravity  down  the  steep 
sides  of  A  and  B,  and  others  would  afterwards  be  blown  by  the  wind 
as  they  fell  off  the  ridges,  and  would  settle  in  the  hollow,  which 
would  thus  become  more  and  more  effaced  as  the  strata  accumulated 
from  c  to  e.  This  levelling  operation  may  perhaps  be  rendered  more 
clear  to  the  student  by  supposing  a  number  of  parallel  trenches  to  be 
dug  in  a  plain  of  moving  sand,  like  the  African  desert,  in  which  case 
the  wind  would  soon  cause  all  signs  of  these  trenches  to  disappear, 
and  the  surface  would  be  as  uniform  as  before.  Now,  water  in 
motion  can  exert  this  levelling  power  on  similar  materials  more 
easily  than  air,  for  almost  all  stones  lose  in  water  more  than  a  third 
of  the  weight  which  they  have  in  air,  the  specific  gravity  of  rocks 
being  in  general  as  2£  when  compared  to  that  of  water,  which  is 
estimated  at  1.  But  the  buoyancy  of  sand  or  mud  would  be  still 
greater  in  the  sea,  as  the  density  of  salt  water  exceeds  that  of  fresh. 


16 


DIAGONAL    OR   CROSS   STRATIFICATION.          [Cn.  II. 


Yet,  however  uniform  and  horizontal  may  be  the  surface  of  new 
deposits  in  general,  there  are  still  many  disturbing  causes,  such  as 
eddies  in  the  water,  and  currents  moving  first  in  one  and  then  in 
another  direction,  which  frequently  cause  irregularities.  We  may 
sometimes  follow  a  bed  of  limestone,  shale,  or  sandstone,  for  a  dis- 
tance of  many  hundred  yards  continuously ;  but  we  generally  find 
at  length  that  each  individual  stratum  thins  out,  and  allows  the  beds 
which  were  previously  above  and  below  it  to  meet.  If  the  materials 
are  coarse,  as  in  grits  and  conglomerates,  the  same  beds  can  rarely 
be  traced  many  yards  without  varying  in  size,  and  often  coming  to  an 
end  abruptly.  (See  fig.  2.) 

Fig.  2. 


Section  of  strata  of  sandstone,  grit,  and  conglomerate.        :>  ••{ 

Diagonal  or  cross  stratification.  —  There  is  also  another  phe- 
nomenon of  frequent  occurrence.  We  find  a  series  of  larger  strata, 
each  of  which  is  composed  of  a  number  of  minor  layers  placed 

Fig.  3. 


Section  of  sand  at  Sandy  Hill,  near  Biggleswade,  Bedfordshire. 
Height  20  feet.    (Green-sand  formauon.) 

obliquely  to  the  general  planes  of  stratification.  To  this  diagonal 
arrangement  the  name  of  "false  or  cross  stratification"  has  been 
given.  Thus  in  the  annexed  section  (fig.  3.)  we  see  seven  or  eight 
large  beds  of  loose  sand,  yellow  and  brown,  and  the  lines  a,  b,  c, 
mark  some  of  the  principal  planes  of  stratification,  which  are  nearly 
horizontal.  But  the  greater  part  of  the  subordinate  laminae  do  not 
conform  to  these  planes,  but  have  often  a  steep  slope,  the  inclination 
being  sometimes  towards  opposite  points  of  the  compass.  When  the 
sand  is  loose  and  incoherent,  as  in  the  case  here  represented,  the 


CH.  II,]         CAUSES    OF    DIAGONAL    STRATIFICATION. 


17 


deviation  from  parallelism  of  the  slanting  laminae  cannot  possibly  be 
accounted  for  by  any  re-arrangement  of  the  particles  acquired  during 
the  consolidation  of  the  rock.  In  what  manner  then  can  such  irre- 
gularities be  due  to  original  deposition  ?  We  must  suppose  that  at 
the  bottom  of  the  sea,  as  well  as  in  the  beds  of  rivers,  the  motions  of 
waves,  currents,  and  eddies  often  cause  mud,  sand,  and  gravel  to  be 
thrown  down  in  heaps  on  particular  spots  instead  of  being  spread 
out  uniformly  over  a  wide  area.  Sometimes,  when  banks  are  thus 
formed,  currents  may  cut  passages  through  them,  just  as  a  river 
forms  its  bed.  Suppose  the  bank  A  (fig.  4.)  to  be  thus  formed  with 


Fig.  4. 


B 


C  D 

a  steep  sloping  side,  and  the  water  being  in  a  tranquil  state,  the  layer 
of  sediment  No.  1.  is  thrown  down  upon  it,  conforming  nearly  to  its 
surface.  Afterwards  the  other  layers,  2,  3,  4,  may  be  deposited  in 
succession,  so  that  the  bank  B  C  D  is  formed.  If  the  current  then 
increases  in  velocity,  it  may  cut  away  the  upper  portion  of  this  mass 
down  to  the  dotted  line  e  (fig.  4.),  and  deposit  the  materials  thus 
removed  farther  on,  so  as  to  form  the  layers  5,  6,  7,  8.  We  have 
now  the  bank  B  C  D  E  (fig.  5.),  of  which  the  surface  is  almost  level 


Fig.  6. 


and  on  which  the  nearly  horizontal  layers,  9,  10,  11,  may  then 
accumulate.  It  was  shown  in  fig.  3.  that  the  diagonal  layers  of  suc- 
cessive strata  may  sometimes  have  an  opposite  slope.  This  is  well 
seen  in  some  cliffs  of  loose  sand  on  the  Suffolk  coast.  A  portion 

of  one  of  these  is  represented  in 
fig.  6.,  where  the  layers,  of  which 
there  are  about  six  in  the  thick- 
ness of  an  inch,  are  composed  of 
quartzose  grains.  This  arrange- 
ment  may  have  been  due  to  the 
altered  direction  of  the  tides  and 

Cliffbetween  Mismer  and  Dunwich.  Currents  in  the  Same  place. 

The  description  above  given  of  the  slanting  position  of  the  minor 
layers  constituting  a  single  stratum  is  in  certain  cases  applicable  on  a 
much  grander  scale  to  masses  several  hundred  feet  thick,  and  many 
miles  in  extent.  A  fine  example  may  be  seen  at  the  base  of  the 
Maritime  Alps  near  Nice.  The  mountains  here  terminate  abruptly 

C 


18  CAUSES   OF    DIAGONAL    STRATIFICATION.          [Cn.  II. 

in  the  sea,  so  that  a  depth  of  many  hundred  fathoms  is  often  found 
within  a  stone's  throw  of  the  beach,  and  sometimes  a  depth  of  3000 
feet  within  half  a  mile.  But  at  certain  points,  strata  of  sand,  marl, 
or  conglomerate,  intervene  between  the  shore  and  the  mountains,  as 
in  the  annexed  fig.  (7.),  where  a  vast  succession  of  slanting  beds 

Monte  Calvo.  Fig.  7. 


Sea 


Section  from  Monte  Calvo  to  the  sea  l>y  the  valley  of  Magnan,  near  Nice. 

A.  Dolomite  and  sandstone.     (Green-sand  formation?) 

a,  b,  d.  Beds  of  gravel  and  sand. 

c.  Fine  marl  and  sand  of  St.  Madeleine,  with  marine  shells. 


of  gravel  and  sand  may  be  traced  from  the  sea  to  Monte  Calvo,  a 
distance  of  no  less  than  9  miles  in  a  straight  line.  The  dip  of  these 
beds  is  remarkably  uniform,  being  always  southward  or  towards  the 
Mediterranean,  at  an  angle  of  about  25°.  They  are  exposed  to  view 
in  nearly  vertical  precipices,  varying  from  200  to  600  feet  in  height, 
which  bound  the  valley  through  which  the  river  Magnan  flows. 
Although,  in  a  general  view,  the  strata  appear  to  be,  parallel  and 
uniform,  they  are  nevertheless  found,  when  examined  closely,  to  be 
wedge-shaped,  and  to  thin  out  when  followed  for  a  few  hundred  feet 
or  yards,  so  that  we  may  suppose  them  to  have  been  thrown  down 
originally  upon  the  side  of  a  steep  bank  where  a  river  or  alpine 
torrent  discharged  itself  into  a  deep  and  tranquil  sea,  and  formed  a 
delta,  which  advanced  gradually  from  the  base  of  Monte  Calvo  to  a 
distance  of  9  miles  from  the  original  shore.  If  subsequently  this 
part  of  the  Alps  and  bed  of  the  sea  were  raised  700  feet,  the  coast 
would  acquire  its  present  configuration,  the  delta  would  emerge,  and 
a  deep  channel  might  then  be  cut  through  it  by  a  river. 

It  is  well  known  that  the  torrents  and  streams,  which  now  descend 
from  the  alpine  declivities  to  the  shore,  bring  down  annually,  when 
the  snow  melts,  vast  quantities  of  shingle  and  sand,  and  then,  as  they 
subside,  fine  mud,  while  in  summer  they  are  nearly  or  entirely  dry  ; 
so  that  it  may  be  safely  assumed,  that  deposits  like  those  of  the  valley 
of  the  Magnan,  consisting  of  coarse  gravel  alternating  with  fine 
sediment,  are  still  in  progress  at  many  points,  as,  for  instance,  at  the 
mouth  of  the  Var.  They  must  advance  upon  the  Mediterranean  in 
the  form  of  great  shoals  terminating  in  a  steep  talus ;  such  being  the 
original  mode  of  accumulation  of  all  coarse  materials  conveyed  into 
deep  water,  especially  where  they  are  composed  in  great  part  of 
pebbles,  which  cannot  be  transported  to  indefinite  distances  by  cur- 
rents of  moderate  velocity.  By  inattention  to  facts  and  inferences 
of  this  kind,  a  very  exaggerated  estimate  has  sometimes  been  made 


CH.  II.]  RIPPLE    MARK.  19 

of  the  supposed  depth  of  the  ancient  ocean.  There  can  be  no  doubt, 
for  example,  that  the  strata  «,  fig.  7.,  or  those  nearest  to  Monte 
Calvo,  are  older  than  those  indicated  by  b,  and  these  again  were 
formed  before  c  ;  but  the  vertical  depth  of  gravel  and  sand  in  any 
one  place  cannot  be  proved  to  amount  even  to  1000  feet,  although 
it  may  perhaps  be  much  greater,  yet  probably  never  exceeding  at 
any  point  3000  or  4000  feet.  But  were  we  to  assume  that  all  the 
strata  were  once  horizontal,  and  that  their  present  dip  or  inclination 
was  due  to  subsequent  movements,  we  should  then  be  forced  to  con- 
clude, that  a  sea  9  miles  deep  had  been  filled  up  with  alternate  layers 
of  mud  and  pebbles  thrown  down  one  upon  another. 

In  the  locality  now  under  consideration,  situated  a  few  miles  to  the 
west  of  Nice,  there  are  many  geological  data,  the  details  of  which 
cannot  be  given  in  this  place,  all  leading  to  the  opinion,  that  when 
the  deposit  of  the  Magnan  was  formed,  the  shape  and  outline  of  the 
alpine  declivities  and  the  shore  greatly  resembled  what  we  now 
behold  at  many  points  in  the  neighbourhood.  That  the  beds,  «,  b,  c,  d, 
are  of  comparatively  modern  date  is  proved  by  this  fact,  that  in  seams 
of  loamy  marl  intervening  between  the  pebbly  beds  are  fossil  shells, 
half  of  which  belong  to  species  now  living  in  the  Mediterranean. 

Hippie  mark.  —  The  ripple  mark,  so  common  on  the  surface  of 
sandstones  of  all  ages  (see  fig.  8.),  and  which  is  so  often  Feen  on  the 

Fig.  8. 


Slab  of  ripple-marked  (new  red)  sandstone  from  Cheshire. 

sea-shore  at  low  tide,  seems  to  originate  in  the  drifting  of  materials 
along  the  bottom  of  the  water,  in  a  manner  very  similar  to  that  which 
may  explain  the  inclined  layers  above  described.  This  ripple  is  not 
entirely  confined  to  the  beach  between  high  and  low  water  mark,  but 
is  also  produced  on  sands  which  are  constantly  covered  by  water. 

c  2 


20  FORMATION    OF    RIPPLE    MARK.  [Cn.  II. 

Similar  undulating  ridges  and  furrows  may  also  be  sometimes  seen 
on  the  surface  of  drift  snow  and  blown  sand.  The  following  is  the 
manner  in  which  I  once  observed  the  motion  of  the  air  to  produce 
this  effect  on  a  large  extent  of  level  beach,  exposed  at  low  tide  near 
Calais.  Clouds  of  fine  white  sand  were  blown  from  the  neighbour- 
ing dunes,  so  as  to  cover  the  shore,  and  whiten  a  dark  level  sur- 
face of  sandy  mud,  and  this  fresh  covering  of  sand  was  beautifully 
rippled.  On  levelling  all  the  small  ridges  and  furrows  of  this  ripple 
over  an  area  of  several  yards  square,  I  saw  them  perfectly  restored  in 
about  ten  minutes,  the  general  direction  of  the  ridges  being  always  at 
right  angles  to  that  of  the  wind.  The  restoration  began  by  the  ap- 
pearance here  and  there  of  small  detached  heaps  of  sand,  which  soon 
lengthened  and  joined  together,  so  as  to  form  long  sinuous  ridges  with 
intervening  furrows.  Each  ridge  had  one  side  slightly  inclined,  and 
the  other  steep  ;  the  lee-side  being  always  steep,  as  £,  c, — d,  e ;  the 
windward-side  a  gentle  slope,  as  «,  b, — c,  d,  fig.  9.  When  a  gust  of 

Fig.  9. 


wind  blew  with  sufficient  force  to  drive  along  a  cloud  of  sand,  all 
the  ridges  were  seen  to  be  in  motion  at  once,  each  encroaching  on 
the  furrow  before  it,  and,  in  the  course  of  a  few  minutes,  filling  the 
place  which  the  furrows  had  occupied.  The  mode  of  advance  was 
by  the  continual  drifting  of  grains  of  sand  up  the  slopes  a  b  and  c  d, 
many  of  which  grains,  when  they  arrived  at  b  and  e?,  fell  over  the 
scarps  b  c  and  d  e}  and  were  under  shelter  from  the  wind ;  so  that 
they  remained  stationary,  resting,  according  to  their  shape  and  mo- 
mentum, on  different  parts  of  the  descent,  and  a  few  only  rolling  to 
the  bottom.  In  this  manner  each  ridge  was  distinctly  seen  to  move 
slowly  on  as  often  as  the  force  of  the  wind  augmented.  Occasionally 
part  of  a  ridge,  advancing  more  rapidly  than  the  rest,  overtook  the 
ridge  immediately  before  it,  and  became  confounded  with  it,  thus 
causing  those  bifurcations  and  branches  which  are  so  common,  and 
two  of  which  are  seen  in  the  slab,  fig.  8.  We  may  observe  this  con- 
figuration in  sandstones  of  all  ages,  and  in  them  also,  as  now  on 
the  sea-coast,  we  may  often  detect  two  systems  of  ripples  interfering 
with  each  other ;  one  more  ancient  and  half  effaced,  and  a  newer  one, 
in  which  the  grooves  and  ridges  are  more  distinct,  and  in  a  different 
direction.  This  crossing  of  two  sets  of  ripples  arises  from  a  change 
of  wind,  and  the  new  direction  in  which  the  waves  are  thrown  on  the 
shore. 

The  ripple  mark  is  usually  an  indication  of  a  sea-beach,  or  of 
water  from  6  to  10  feet  deep,  for  the  agitation  caused  by  waves  even 
during  storms  extends  to  a  very  slight  depth.  To  this  rule,  however, 
there  are  some  exceptions,  and  recent  ripple  marks  have  been  ob- 
served at  the  depth  of  60  or  70  feet.  It  has  also  been  ascertained  that 
currents  or  large  bodies  of  water  in  motion  may  disturb  mud  and 


CH.  III.]    GRADUAL    DEPOSITION    INDICATED    BY   FOSSILS.      21 

sand  at  the  depth  of  300  or  even  450  feet.*  Beach  ripple,  however, 
may  usually  be  distinguished  from  current  ripple  by  frequent  changes 
in  its  direction.  In  a  slab  of  sandstone,  not  more  than  an  inch  thick, 
the  furrows  or  ridges  of  an  ancient  ripple  may  often  be  seen  in  several 
successive  lamina?  to  run  towards  different  points  of  the  compass. 


CHAPTER  HI. 

ARRANGEMENT    OF    FOSSILS   IN    STRATA FRESHWATER    AND    MARINE. 

Successive  deposition  indicated  by  fossils  —  Limestones  formed  of  corals  and  shells — 
Proofs  of  gradual  increase  of  strata  derived  from  fossils  —  Serpula  attached  to 
spatangus — Wood  bored  by  teredina — Tripoli  and  semi-opal  formed  of  infusoria 
— Chalk  derived  principally  from  organic  bodies — Distinction  of  freshwater  from 
marine  formations —  Genera  of  freshwater  and  land  shells — Rules  for  recognizing 
marine  testacea — Gyrogonite  and  chara — Freshwater  fishes — Alternation  of 
marine  and  freshwater  deposits — Lym- Fiord. 

HAVING  in  the  last  chapter  considered  the  forms  of  stratification  so 
far  as  they  are  determined  by  the  arrangement  of  inorganic  matter, 
we  may  now  turn  our  attention  to  the  manner  in  which  organic  re- 
mains are  distributed  through  stratified  deposits.  We  should  often 
be  unable  to  detect  any  signs  of  stratification  or  of  successive  deposi- 
tion, if  particular  kinds  of  fossils  did  not  occur  here  and  there  at 
certain  depths  in  the  mass.  At  one  level,  for,  example,  univalve  shells 
of  some  one  or  more  species  predominate  ;  at  another,  bivalve  shells ; 
and  at  a  third,  corals ;  while  in  some  formations  we  find  layers  of 
vegetable  matter,  commonly  derived  from  land  plants,  separating 
strata. 

It  may  appear  inconceivable  to  a  beginner  how  mountains,  several 
thousand  feet  thick,  can  have  become  filled  with  fossils  from  top  to 
bottom ;  but  the  difficulty  is  removed,  when  he  reflects  on  the  origin 
of  stratification,  as  explained  in  the  last  chapter,  and  allows  sufficient 
time  for  the  accumulation  of  sediment.  He  must  never  lose  sight  of 
the  fact  that,  during  the  process  of  deposition,  each  separate  layer 
was  once  the  uppermost,  and  covered  immediately  by  the  water  in 
which  aquatic  animals  lived.  Each  stratum  in  fact,  however  far  it 
may  now  lie  beneath  the  surface,  was  once  in  the  state  of  shingle,  or 
loose  sand  or  soft  mud  at  the  bottom  of  the  sea,  in  which  shells  and 
other  bodies  easily  became  enveloped. 

By  attending  to  the  nature  of  these  remains,  we  are  often  enabled 
to  determine  whether  the  deposition  was  slow  or  rapid,  whether  it 
took  place  in  a  deep  or  shallow  sea,  near  the  shore  or  far  from  land, 
and  whether  the  water  was  salt,  brackish,  or  fresh.  Some  limestones 
consist  almost  exclusively  of  corals,  and  in  many  cases  it  is  evident 

*  Edin.  New  Phil.  Journ.  vol.  xxxi.;  and  Darwin,  Vole.  Islands,  p.  134. 

c  3 


22 


GRADUAL   DEPOSITIONS 


[CH.  III. 


that  the  present  position  of  each  fossil  zoophyte  has  been  determined 
by  the  manner  in  which  it  grew  originally.  The  axis  of  the  coral, 
for  example,  if  its  natural  growth  is  erect,  still  remains  at  right  angles 
to  the  plane  of  stratification.  If  the  stratum  be  now  horizontal,  the 
round  spherical  heads  of  certain  species  continue  uppermost,  and 
their  points  of  attachment  are  directed  downwards.  This  arrange- 
ment is  sometimes  repeated  throughout  a  great  succession  of  strata. 
From  what  we  know  of  the  growth  of  similar  zoophytes  in  modern 
reefs,  we  infer  that  the  rate  of  increase  was  extremely  slow,  and  some 
of  the  fossils  must  have  nourished  for  ages  like  forest  trees,  before 
they  attained  so  large  a  size.  During  these  ages,  the  water  remained 
clear  and  transparent,  for  such  corals  cannot  live  in  turbid  water. 

In  like  manner,  when  we  see  thousands  of  full-grown  shells  dis- 
persed every  where  throughout  a  long  series  of  strata,  we  cannot 
doubt  that  time  was  required  for  the  multiplication  of  successive 
generations  ;  and  the  evidence  of  slow  accumulation  is  rendered  more 
striking  from  the  proofs,  so  often  discovered,  of  fossil  bodies  having 
lain  for  a  time  on  the  floor  of  the  ocean  after  death  before  they  were 
imbedded  in  sediment.  Nothing,  for  example,  is  more  common  than 
to  see  fossil  oysters  in  clay,  with  serpulse,  or  barnacles  (acorn-shells), 
or  corals,  and  other  creatures,  attached  to  the  inside  of  the  valves,  so 
that  the  mollusk  was  certainly  not  buried  in  argillaceous  mud  the 
moment  it  died.  There  must  have  been  an  interval  during  which  it 
was  still  surrounded  with  clear  water,  when  the  creatures  whose  re- 
mains now  adhere  to  it,  grew  from  an  embryo  to  a  mature  state. 
Attached  shells  which  are  merely  external,  like  some  of  the  ser- 
pulae  (a)  in  the  annexed  figure  (fig.  10.),  may  often  have  grown 
upon  an  oyster  or  other  shell  while  the  animal  within  was  still  living; 

but  if  they  are  found  on  the  inside, 
it  could  only  happen  after  the 
death  of  the  inhabitant  of  the  shell 
which  affords  the  support.  Thus, 
in  fig.  10.,  it  will  be  seen  that  two 
serpulse  have  grown  on  the  inte- 
rior, one  of  them  exactly  on  the 
place  where  the  adductor  muscle 
of  the  Gryphcea  (a  kind  of  oyster) 
was  fixed. 

Some  fossil  shells,  even  if  simply 
attached  to  the  outside  of  others, 
bear  full  testimony  to  the  conclu- 
sion above  alluded  to,  namely,  that 
an  interval  elapsed  between  the 
death  .of  the  creature  to  whose 
shell  they  adhere,  and  the  burial  of 
the  same  in  mud  or  sand.  The  sea- 
urchins  or  Echini,  so  abundant  in 
white  chalk,  afford  a  good  illustra- 
tion.  It  is  well  known  that  these 


Fig.  10. 


Foss 


CH.  III.] 


INDICATED    BY   FOSSILS. 


23 


animals,  when  living,  are  invariably  covered  with  numerous  suckers, 
or  gelatinous  tubes,  called  "ambulacral,"  because  they  serve  as  organs 
of  motion.  They  are  also  armed  with  spines  supported  by  rows  of 
tubercles.  These  last  are  only  seen  after  the  death  of  the  sea-urchin, 
when  the  spines  have  dropped  off.  In  fig.  12.  a  living  species  of 
Spatangus,  common  on  our  coast,  is  represented  with  one  half  of  its 

Fig.  11.  Fig.  12. 


Serpula  attached  to 

a  fostJl  Spatangus. 

from  the  chalk. 


Recent  Spatangus  with  the  spines 
removed  from  one  side. 

b .   Spine  and  tubercles,  nat.  size. 
a.  The  same  magnified. 


shell  stripped  of  the  spines.  In  fig.  11.  a  fossil  of  the  same  genus 
from  the  white  chalk  of  England  shows  the  naked  surface  which  the 
individuals  of  this  family  exhibit  when  denuded  of  their  bristles. 
The  full-grown  Serpula^  therefore,  which  now  adheres  externally, 
could  not  have  begun  to  grow  till  the  Spatangus  had  died,  and  the 
spines  were  detached. 

Now  the  series  of  events  here  attested  by  a  single  fossil  may  be 
carried  a  step  farther.  Thus,  for  example,  we  often  meet  with  a  sea- 
urchin  in  the  chalk  (see  fig.  13.),  which  has  fixed  to  it  the  lower 
valve  of  a  Crania,  a  genus  of  bivalve  mollusca.  The  upper  valve 
Fig.  13.  (^  %•  13.)  is  almost  invariably  wanting,  though 

occasionally  found^n  a  perfect  state  of  preservation 
in  white  chalk  at  some  distance.  In  this  case,  we 
see  clearly  that  the  sea-urchin  first  lived  from  youth 
to  age,  then  died  and  lost  its  spines,  which  were 
carried  away.  Then  the  young  Crania  adhered 
to  the  bared  shell,  grew  and  perished  in  its  turn ; 
after  which  the  upper  valve  was  separated  from 
ftCrup?er"vaihveed'of  the  the  lower  before  the  Echinus  became  enveloped  in 

Crania  detached.  chalky  mud. 

It  may  be  well  to  mention  one  more  illustration  of  the  manner  in 
which  single  fossils  may  sometimes  throw  light  on  a  former  state  of 
things,  both  in  the  bed  of  the  ocean  and  on  some  adjoining  land.  We 
meet  with  many  fragments  of  wood  bored  by  ship-worms  at  various 
depths  in  the  clay  on  which  London  is  built.  Entire  branches  and 
stems  of  trees,  several  feet  in  length,  are  sometimes  dug  out,  drilled 
all  over  by  the  holes  of  these  borers,  the  tubes  and  shells  of  the  mol- 
lusk  still  remaining  in  the  cylindrical  hollows.  In  fig.  1 5.  e,  a  re- 
presentation is  given  of  a  piece  of  recent  wood  pierced  by  the  Teredo 
navalis,  or  common  ship-worm,  which  destroys  wooden  piles  and 
ships.  When  the  cylindrical  tube  d  has  been  extracted  from  the 
wood,  a  shell  is  seen  at  the  larger  extremity,  composed  of  two  pieces, 
as  shown  at  c.  In  like  manner,  a  piece  of  fossil  wood  (a,  fig.  14.) 

c  4 


24 


SLOW    DEPOSITION    OF   STRATA. 


has  been  perforated  by  an  animal  of  a  kindred  but  extinct  genus, 
called  Teredina  by  Lamarck.  The  calcareous  tube  of  this  mollusk 
was  united  and  as  it  were  soldered  on  to  the  valves  of  the  shell  (b\ 

Fig.  14. 


Fig.  15. 


Fossil  and  recent  wood  drilled  by  perforating  Mollusca. 

Fig.  14.  a.  Fossil  wood  from  London  clay,  bored  by  Teredina. 

b.  Shell  and  tube  of  Teredina  personata,  the  right-hand  figure  the  ventral,  the  left  the 

dorsal  view. 

Fig.  15.  e.  Recent  wood  bored  by  Teredo. 

d.  Shell  and  tube  of  Teredo  navalis,  from  the  same. 

c.  Anterior  and  posterior  view  of  the  valves  of  same  detached  from  the  tube. 

which  therefore  cannot  be  detached  from  the  tube,  like  the  valves  of 
the  recent  Teredo.  The  wood  in  this  fossil  specimen  is  now  con- 
verted into  a  stony  mass,  a  mixture  of  clay  and  lime;  but  it  must 
once  have  been  buoyant  and  floating  in  the  sea,  when  the  Teredines 
lived  upon  it,  perforating  it  in  all  directions.  Again,  before  the 
infant  colony  settled  upon  the  drift  wood,  the  branch  of  a  tree  must 
have  been  floated  down  to  the  sea  by  a  river,  uprooted,  perhaps,  by  a 
flood,  or  torn  off  and  cast  into  the  waves  by  the  wind :  and  thus  our 
thoughts  are  carried  back  to  a  prior  period,  when  the  tree  grew  for 
years  on  dry  land,  enjoying  a  fit  soil  and  climate. 

It  has  been  already  remarked  that  there  are  rocks  in  the  interior 
of  continents,  at  various  depths  in  the  earth,  and  at  great  heights 
above  the  sea,  almost  entirely  made  up  of  the  remains  of  zoophytes 
and  testacea.  Such  masses  may  be  compared  to  modern  oyster-beds 
and  coral-reefs ;  and,  like  them,  the  rate  of  increase  must  have  been 
extremely  gradual.  But  there  are  a  variety  of  stony  deposits  in  the 
earth's  crust,  now  proved  to  have  been  derived  from  plants  and 
animals  of  which  the  organic  origin  was  not  suspected  until  of  late 
years,  even  by  naturalists.  Great  surprise  was  therefore  created  by 
the  recent  discovery  of  Professor  Ehrenberg,  of  Berlin,  that  a  certain 
kind  of  siliceous  stone,  called  tripoli,  was  entirely  composed  of  mil- 
lions of  the  remains  of  organic  beings,  which  the  Prussian  naturalist 
refers  to  microscopic  Infusoria,  but  which  most  others  now  believe  to 
be  plants.  They  abound  in  freshwater  lakes  and  ponds  in  England 
and  other  countries,  and  are  termed  Diatomaceae  by  those  naturalists 
who, believe  in  their  vegetable  origin.  The  substance  alluded  to  has 


CH.  III.] 


INFUSORIA   OF    TRIPOLI. 


25 


long  been  well  known  in  the  arts,  being  used  in  the  form  of  powder 
for  polishing  stones  and  metals.  It  has  been  procured,  among  other 
places,  from  Bilin,  in  Bohemia,  where  a  single  stratum,  extending 
over  a  wide  area,  is  no  less  than  14  feet  thick.  This  stone,  when  ex- 
amined with  a  powerful  microscope,  is  found  to  consist  of  the  sili- 

Fig.  16.  Fig.  17.  Fig.  18. 


Gaillonella 
distans. 


Gaillonella 
ferruginea. 


Fig.  20. 


Fig.  19. 


D 


These  figures  are  magnified  nearly  300  times,  except  the  lower  figure  of  G.  ferruginea  (fig.  18  a) 
which  is  magnified  2000  times. 

ceous  plates  or  frustules  of  the  above-mentioned  Diatomaceze,  united 
together  without  any  visible  cement.  It  is  difficult- to  convey  an  idea 
of  their  extreme  minuteness ;  but  Ehrenberg  estimates  that  in  the 
Bilin  tripoli  there  are  41,000  millions  of  individuals  of  the  Gaillonella 
distans  (see  fig.  17.)  in  every  cubic  inch,  which  weighs  about  220 
grains,  or  about  187  millions  in  a  single  grain.  At  every  stroke, 
therefore,  that  we  make  with  this  polishing  powder,  several  millions, 
perhaps  tens  of  millions,  of  perfect  fossils  are  crushed  to  atoms. 

The  remains  of  these  Diatomacese  are  of  pure  silex,  and  their  forms 
are  various,  but  very  marked   and   constant  in  particular  genera 

and  species.  Thus,  in  the 
family  Bacillaria  (see  fig. 
16.),  the  fossils  preserved 
in  tripoli  are  seen  to  ex- 
hibit the  same  divisions 
and  transverse  lines  which 
characterize  the  living  spe- 
cies of  kindred  form.  With 
these,  also,  the  siliceous 
spiculae  or  internal  sup- 
ports of  the  freshwater 
sponge,  or  Spongilla  of 
Lamarck,  are  sometimes  in- 
termingled (see  the  needle- 
shaped  bodies  in  fig.  20.). 
These  flinty  cases  and  spi- 
culae, although  hard,  are 
very  fragile,  breaking  like 
glass,  and  are  therefore 
admirably  adapted,  when 
rubbed,  for  wearing  down 
into  a  fine  powder  fit  for 

Fragment  of  semi-opal  from  the  great  bed  of  tripoli,  Bilin.    polishing      the      Surface      of 

Fig.  19.    Natural  size.  metals. 

Fig.  20.     The  same  magnified,  showing  circular  articula-       T>      -^       J.-L     4-   'vwVU    PnvmnA 
tions  of  a  species  of  Gaillonella,  and  spiculae  of       Besides  the  tripoli,  lormed 

sP°nefaa-  exclusively    of  the   fossils 


26  FOSSIL  INFUSORIA.  [Cn.  III. 

above  described,  there  occurs  in  the  upper  part  of  the  great  stratum 
at  Bilin  another  heavier  and  more  compact  stone,  a  kind  of  semi- 
opal,  in  which  innumerable  parts  of  Diatomacese  and  spiculse  of  the 
Spongilla  are  filled  with,  and  cemented  together  by,  siliceous  matter. 
It  is  supposed  that  the  siliceous  remains  of  the  most  delicate  Dia- 
tomaceje  have  been  dissolved  by  water,  and  have  thus  given  rise  to 
this  opal  in  which  the  more  durable  fossils  are  preserved  like  insects 
in  amber.  This  opinion  is  confirmed  by  the  fact  that  the  organic 
bodies  decrease  in  number  and  sharpness  of  outline  in  proportion  as 
the  opaline  cement  increases  in  quantity. 

In  the  Bohemian  tripoli  above  described,  as  in  that  of  Planitz  in 
Saxony,  the  species  of  Diatomaceae  (or  Infusoria,  as  termed  by  Ehren- 
berg)  are  freshwater  ;  but  in  other  countries,  as  in  the  tripoli  of  the 
Isle  of  France,  they  are  of  marine  species,  and  they  all  belong  to 
formations  of  the  tertiary  period,  which  will  be  spoken  of  hereafter. 

A  well-known  substance,  called  bog-iron  ore,  often  met  with  in 
peat-mosses,  has  also  been  shown  by  Ehrenberg  to  consist  of  innu- 
merable articulated  threads,  of  a  yellow  ochre  colour,  composed 
partly  of  flint  and  partly  of  oxide  of  iron.  These  threads  are  the 
cases  of  a  minute  microscopic  body,  called  Gaillonella  ferruginea 
(fig.  18.). 

It  is  clear  that  much  time  must  have  been  required  for  the  accu- 
mulation of  strata  to  which  countless  generations  of  Diatomaceae  have 
contributed  their  remains ;  and  these  discoveries  lead  us  naturally  to 
suspect  that  other  deposits,  of  which  the  materials  have  usually  been 
supposed  to  be  inorganic,  may  in  reality  have  been  derived  from 
microscopic  organic  bodies.  That  this  is  the  case  with  the  white 
chalk,  has  often  been  imagined,  this  rock  having  been  observed  to 
abound  in  a  variety  of  marine  fossils,  such  as  echini,  testacea, 
bryozoa,  corals,  sponges,  Crustacea,  and  fishes.  Mr.  Lonsdale,  on 
examining,  in  Oct.  1835,  in  the  museum  of  the  Geological  Society  of 
London,  portions  of  white  chalk  from  different  parts  of  England, 
found,  on  carefully  pulverizing  them  in  water,  that  what  appear  to 
the  eye  simply  as  white  grains  were,  in  fact,  well  preserved  fossils. 
He  obtained  above  a  thousand  of  these  from  each  pound  weight  of 
chalk,  some  being  fragments  of  minute  bryozoa  and  corallines,  others 
entire  Foraminifera  and  Cytheridae.  The  annexed  drawings  will 
give  an  idea  of  the  beautiful  forms  of  many  of  these  bodies.  The 
figures  a  a  represent  their  natural  size,  but,  minute  as  they  seem,  the 

Cytheridae  and  Foraminifera  from  the  chalk. 
Fig.  21.  Fig.  22.  Fig.  23.  Fig.  24. 


Cythere,  Mull.  Portion  of  Cristellaria  Rosalina. 

Cytherina,  Lam.  Nodosaria.  rotulata. 

smallest  of  them,  such  as  a,  fig.  24.,  are  gigantic  in  comparison  with 
the  cases  of  Diatomaceae  before  mentioned.  It  has,  moreover,  been 
lately  discovered  that  the  chambers  into  which  these  Foraminifera 


CH.  III.]  FRESHWATER   AND   MARINE    FOSSILS.  27 

are  divided  are  actually  often  filled  with  thousands  of  well-preserved 
organic  bodies,  which  abound  in  every  minute  grain  of  chalk,  and 
are  especially  apparent  in  the  white  coating  of  flints,  often  accom- 
panied by  innumerable  needle-shaped  spiculae^  of  sponges.  After 
reflecting  on  these  discoveries,  we  are  naturally  led  on  to  conjecture 
that,  as  the  formless  cement  in  the  semi-opal  of  Bilin  has  been 
derived  from  the  decomposition  of  animal  and  vegetable  remains,  so 
also  many  chalk  flints  in  which  no  organic  structure  can  be  re- 
cognized may  nevertheless  have  constituted  a  part  of  microscopic 
animalcules. 

"  The  dust  we  tread  upon  was  once  alive  ! " — BYRON. 

How  faint  an  idea  does  this  exclamation  of  the  poet  convey  of 
the  real  wonders  of  nature!  for  here  we  discover  proofs  that  the 
calcareous  and  siliceous  dust  of  which  hills  are  composed  has  not 
only  been  once  alive,  but  almost  every  particle,  albeit  invisible  to 
the  naked  eye,  still  retains  the  organic  structure  which,  at  periods 
of  time  incalculably  remote,  was  impressed  upon  it  by  the  powers 
of  life. 

Freshwater  and  marine  fossils.  —  Strata,  whether  deposited  in  .salt 
or  fresh  water,  have  the  same  forms ;  but  the  imbedded  fossils  are 
very  different  in  the  two  cases,  because  the  aquatic  animals  which 
frequent  lakes  and  rivers  are  distinct  from  those  inhabiting  the  sea. 
In  the  northern  part  of  the  Isle  of  Wight  formations  of  marl  and 
limestone,  more  than  50  feet  thick,  occur,  in 'which  the  shells  are 
principally,  if  not  all,  of  extinct  species.  Yet  we  recognize  their 
freshwater  origin,  because  they  are  of  the  same  genera  as  those  now 
abounding  in  ponds  and  lakes,  either  in  our  own  country  or  in 
warmer  latitudes. 

In  many  parts  of  France,  as  in  Auvergne,  for  example,  strata  of 
limestone,  marl,  and  sandstone  are  found,  hundreds  of  feet  thick, 
which  contain  exclusively  freshwater  and  land  shells,  together  with 
the  remains  of  terrestrial  quadrupeds.  The  number  of  land  shells 
scattered  through  some  of  these  freshwater  deposits  is  exceedingly 
great ;  and  there  are  districts  in  Germany  where  the  rocks  scarcely 
contain  any  other  fossils  except  snail-shells  (helices) ;  as,  for  instance, 
the  limestone  on  the  left  bank  of  the  Rhine,  between  Mayence  and 
Worms,  at  Oppenheim,  Findheim,  Budenheim,  and  other  places.  In 
order  to  account  for  this  phenomenon,  the  geologist  has  only  to 
examine  the  small  deltas  of  torrents  which  enter  the  Swiss  lakes 
when  the  waters  are  low,  such  as  the  newly-formed  plain  where  the 
Kander  enters  the  Lake  of  Thun.  He  there  sees  sand  and  mud 
strewed  over  with  innumerable  dead  land  shells,  which  have  been 
brought  down  from  valleys  in  the  Alps  in  the  preceding  spring, 
during  the  melting  of  the  snows.  Again,  if  we  search  the  sands  on 
the  borders  of  the  Rhine,  in  the  lower  part  of  its  course,  we  find 
countless  land  shells  mixed  with  others  of  species  belonging  to  lakes, 
stagnant  pools,  and  marshes.  These  individuals  have  been  washed 


28 


DISTINCTION   OP   FRESHWATER 


[CH.  III. 


away  from  the  alluvial  plains  of  the  great  river  and  its  tributaries, 
some  from  mountainous  regions,  others  from  the  low  country. 

Although  freshwater  formations  are  often  of  great  thickness,  yet 
they  are  usually  very  limited  in  area  when  compared  to  marine 
deposits,  just  as  lakes  and  estuaries  are  of  small  dimensions  in  com- 
parison with  seas. 

,  We  may  distinguish  a  freshwater  formation,  first,  by  the  absence 
of  many  fossils  almost  invariably  met  with  in  marine  strata.  For 
example,  there  are  no  sea-urchins,  no  corals,  and  scarcely  any  zoo- 
phytes ;  no  chambered  shells,  such  as  the  nautilus,  nor  microscopic 
Foraminifera.  But  it  is  chiefly  by  attending  to  the  forms  of  the 
mollusca  that  we  are  guided  in  determining  the  point  in  question. 
In  a  freshwater  deposit,  the  number  of  individual  shells  is  often  as 
great,  if  not  greater,  than  in  a  marine  stratum ;  but  there  is  a  smaller 
variety  of  species  and  genera.  This  might  be  anticipated  from  the 
fact  that  the  genera  and  species  of  recent  freshwater  and  land  shells 
are  few  when  contrasted  with  the  marine.  Thus,  the  genera  of  true 
mollusca  according  to  Blainville's  system,  excluding  those  of  extinct 
species  and  those  without  shells,  amount  to  about  200  in  number,  of 
which  the  terrestrial  and  freshwater  genera  scarcely  form  more  than 
a  sixth.* 

Almost  all  bivalve  shells,  or  those  of  acephalous  mollusca,  are 
marine,  about  ten  only  out  of  ninety  genera  being  freshwater. 


Fig.  25. 


Fig.  26. 


Cyclas  obovata  ;  fossil.    Hants. 


Cyrena  consobrina  ;  fossil.    Grays,  Essex. 


Among  these  last,  the  four  most  common  forms,  both  recent  and 
fossil,  are  Cyclas,   Cyrena,   Unio,  and  Anodonta  (see  figures);  the 


Fig.  27. 


Fig.  28. 


Anodonta  Cordierii; 
fossil.    Paris. 


Anodonta  latimargfnattis  ; 
recent.    Bahia. 


Unio  littoralis  ; 
recent.    Auvergne. 


two  first  and  two  last  of  which  are  so  nearly  allied  as  to  pass  into 
each  other. 


*  See  Synoptic  Table  in  Blainville's  Malacologie. 


OH.  III.] 


FROM    MARINE    FORMATIONS. 


29 


Lamarck  divided  the  bivalve  mollusca  into 
the  Dimyary,  or  those  having  two  large  mus- 
cular impressions  in  each  valve,  as  a  b  in  the 
Cyclas,  fig.  25.,  and  the  Monomyary,  such  as 
the  oyster  and  scallop,  in  which  there  is  only 
one  of  these  impressions,  as  is  seen  in  fig.  30. 
Now,  as  none  of  these  last,  or  the  unimuscular 
bivalves,  are  freshwater,  we  may  at  once  pre- 
sume a  deposit  in  which  we  find  any  of  them 
to  be  marine. 

Gryphceaincurvcii  Sow.(G.  ar~  «       -i  i     n 

cuata,  Lam.)  upper  valve.  Lias.      The   univalve  shells  most   characteristic  of 


fresh-water  deposits  are,  Planorbis,  Lymnea,  and  Paludina. 

Fig.  31.  Fig.  32.  Fig.  33. 


(See 


Planorbis  euomphalus  ; 
fossil.    Isle  of  Wight. 


Paludina  lenta  ; 
fossil.    Hants. 


Lymnea  longt'scata  ; 
fossil.    Hants. 

figures.)     But   to   these   are   occasionally  added   Physa.    Succinea, 
Ancylus,  Valvata,  Melanopsis,  Melania,  and  Neritina.    (See  figures.) 

Fig.  34.  Fig.  35.        .  Fig.  36.  Fig.  37. 


Succmea  amphibia  ; 
fossil.    Loess,  Rhine. 


Ancylus  elegans  ; 
fossil.    Hants. 


Valvata : 
fossil. 
Grays,  Essex. 


Physa  hypnoruin  ; 
recent. 


In   regard   to   one   of  these,    the  Ancylus   (fig.  35.),    Mr.  Gray 
observes   that  it  sometimes  differs  in  no  respect  from  the  marine 

Fig.  38.  Fig.  39.  Fig.  40.  Fig.  41. 


Auricula  ; 
recent.     Ava. 


Physa  culum- 
naris.  Paris, 
basin. 


Melanopsis  buc- 
cinoidea  ;  recent. 

Asia. 


Paris  basin. 

Siphonaria,   except   in   the   animal.     The   shell,   however,   of  the 
Ancylus  is  usually  thinner.*  t 

*  Gray,  Phil.  Trans.,  1835,  p.  302. 


30  DISTINCTION    OF    FRESHWATER  [OH.  III. 

Some    naturalists   include   Neritina   (fig.  42.)    and    the    marine 
Nerita  (fig.  43.)  in  the  same  genus,  it  being   scarcely  possible  to 


Fig.  42. 


Fig   43. 


Fig.  14. 


Neritina  globulus.    Paris  basin.  Nerita  granulosa.    Paris  basin. 

distinguish  the  two  by  good  generic  characters.  But,  as 
a  general  rule,  the  fluviatile  species  are  smaller,  smoother, 
and  more  globular  than  the  marine  ;  and  they  have  never, 
like  the  Neritcs,  the  inner  margin  of  the  outer  lip  toothed 
or  crenulated.  (See  fig.  43.) 

A  few  genera,  among  which  Cerithium  (fig.  44.)  is  the 
most  abundant,  are  common  both  to  rivers  and  the  sea, 
having  species  peculiar  to  each.  Other  genera,  like  Auri- 
cula  (fig.  38.),  are  amphibious,  frequenting  marshes,  espe- 
cially  near  the  sea. 

The  terrestrial  shells  are  all  univalves.  The  most  abundant 
genera  among  these,  both  in  a  recent  and  fossil  state,  are  Helix 
(fig.  45.),-  Cyclostoma  (fig.  46.),  Pupa  (fig.  47.),  Clausilia  (fig.  48.), 


Fig.  45. 


Fig.  46. 


Fig.  47.          Fig.  48. 


Fig  49. 


Helix  Turoncnsis. 
Faluns,  Touraine. 


Pupa 
tridens. 
Loess. 


Clausilia 
biriens. 
Loess. 


Bulimus  lubncus. 
Loess,  Rhine. 


Bulimus  (fig.  49.),  and  Achatina ;  which  two  last  are  nearly  allied 
and  pass  into  each  other. 

The  Ampullaria  (fig.  50.),  is  another  genus  of  shells,  inhabiting 
Fig.  50.  rivers  and   ponds   in   hot   countries.     Many  fossil 

species  have  been  referred  to  this  genus,  but  they 
have  been  found  chiefly  in  marine  formations,  and 
are  suspected  by  some  conchologists  to  belong  to 
Natica  and  other  marine  genera. 

All  univalve  shells  of  land  and  freshwater  spe- 
cies, with  the  exception  of  Melanopsis  (fig.  41.), 
and  Achatina,  which  has  a  slight  indentation,  have 
entire  mouths;  and  this  circumstance  may  often 
serve  as  a  convenient  rule  for  distinguishing  freshwater  from  marine 
strata ;  since,  if  any  univalves  occur  of  which  the  mouths  are  not 
entire,'  we  may  presume  that  the  formation  is  marine.  The  aper- 
ture is  said  to  be  entire  in  such  shells  as  the  Ampullaria  and  the 
land  shells  (figs.  45  —  49.),  when  its  outline  is  not  interrupted 
by  an  indentation  or  notch,  such  as  that  seen  at  b  in  Ancillaria 


CH.   II L]  FROM    MARINE    FORMATIONS.  31 

(fig.  52.) ;  or  is  not  prolonged  into  a  canal,  as  that  seen  at  a  in 
Pleurotoma  (fig.  51.). 

The  mouths  of  a  large  proportion  of  the  marine  univalves  have 
these  notches  or  canals,  and  almost  all  such  species  are  carnivorous ; 

Fig.  51.  Fig.  52. 


Pleurotoma 

rotata. 

Subap.  hills, 

Italy. 


a  b 

Ancillar'ia  subulata.     London  clay. 

whereas  nearly  all  testacea  having  entire  mouths,  are  plant-eaters ; 
whether  the  species  be  marine,  freshwater,  or  terrestrial. 

There  is,  however,  one  genus  which  affords  an  occasional  ex- 
ception to  one  of  the  above  rules.  The  Cerithium  (fig.  44.), 
although  provided  with  a  short  canal,  comprises  some  species  which 
inhabit  salt,  others  brackish,  and  others  fresh  water,  and  they  are 
said  to  be  all  plant-eaters. 

Among  the  fossils  very  common  in  freshwater  deposits  are  the 
shells  of  Cypris,  a  minute  crustaceous  animal,  having  a  shell  much 
resembling  tha  of  the  bivalve  mollusca.*  Many  minute  living 
species  of  this  genus  swarm  in  lakes  and  "stagnant  pools  in  Great 
Britain  ;  but  their  shells  are  not,  if  considered  separately,  conclusive 
as  to  the  freshwater  origin  of  a  deposit,  because  the  majority  of 
species  in  another  kindred  genus  of  the  same  order,  the  Cytherina  of 
Lamarck  (see  above,  fig.  21.  p.  26.),  inhabit  salt  water;  and,  although 
the  animal  differs  slightly,  the  shell  is  scarcely  distinguishable  from 
that  of  the  Cypris. 

The  seed-vessels  and  stems  of  Chara,  a  genus  of  aquatic  plants, 
are  very  frequent  in  freshwater  strata.  These  seed-vessels  were 
called,  before  their  true  nature  was  known,  gyrogonites,  and  were 
supposed  to  be  foraminiferous  shells.  (See  fig.  53.  a.) 

The  CharcB  inhabit  the  bottom  of  lakes  and  ponds,  and  flourish 
mostly  where  the  water  is  charged  with  carbonate  of  lime.  Their 
seed-vessels  are  covered  with  a  very  tough  integument,  capable  of 
resisting  decomposition ;  to  which  circumstance  we  may  attribute 
their  abundance  in  a  fossil  state.  The  annexed  figure  (fig.  54.) 
represents  a  branch  of  one  of  many  new  species  found  by  Professor 
Amici  in  the  lakes  of  Northern  Italy.  The  seed-vessel  in  this  plant 
is  more  globular  than  in  the  British  Char<z,  and  therefore  more 
nearly  resembles  in  form  the  extinct  fossil  species  found  in  England, 

*  For  figures  of  fossil  species  of  Purbeck,  see  below,  ch.  xx. 


32  FRESHWATER    AND   MARINE    FORMATIONS.       [Cn.  III. 

France,  and  other  countries.     The  stems,  as  well  as  the  seed-vessels, 
of  these   plants   occur  both  in  modern  shell  marl  and  in  ancient 

Fig.  53.  Fig.  54. 


Chara  medicaginula ;  Chara  elastfca ;  recent.    Italy, 
fossil.    Upper  Eocene,  Isle  of  Wight. 

a.  Sessile  seed  vessel  between  the  divisions  of 

a.  Seed-vessel,  the  leaves  of  the  female  plant. 

magnified  20  b.  Magnified  transverse  section  of"  a  branch, 

diameters.  with  five  seed-vessels,  seen  from  below 

b.  Stem,  magnified.  upwards. 

freshwater  formations.  They  are  generally  composed  of  a  large 
tube  surrounded  by  smaller  tubes  ;  the  whole  stem  being  divided  at 
certain  intervals  by  transverse  partitions  or  joints.  (See  b,  fig.  53.) 

It  is  not  uncommon  to  meet  with  layers  of  vegetable  matter, 
impressions  of  leaves,  and  branches  of  trees,  in  strata  containing 
freshwater  shells ;  and  we  also  find  occasionally  the  teeth  and  bones 
of  land  quadrupeds,  of  species  now  unknown.  The  manner  in 
which  such  remains  are  occasionally  carried  by  rivers  into  lakes, 
especially  during  floods,  has  been  fully  treated  of  in  the  "  Principles 
of  Geology."* 

The  remains  of  fish  are  occasionally  useful  in  determining  the 
freshwater  origin  of  strata.  Certain  genera,  such  as  carp,  perch, 
pike,  and  loach  (Cyprinus,  Perca,  Esox,  and  Cobitis),  as  also  Lebias, 
being  peculiar  to  freshwater.  Other  genera  contain  some  freshwater 
and  some  marine  species,  as  Cottus,  Mugil,  and  Anguilla,  or  eel. 
The  rest  are  either  common  to  rivers  and  the  sea,  as  the  salmon ;  or 
are  exclusively  characteristic  of  salt  water.  The  above  observa- 
tions respecting  fossil  fishes  are  applicable  only  .to  the  more 
modern  or  tertiary  deposits ;  for  in  the  more  ancient  rocks  the 
forms  depart  so  widely  from  those  of  existing  fishes,  that  it  is  very 
difficult,  at  least  in  the  present  state  of  science,  to  derive  any  positive 
information  from  icthyolites  respecting  the  element  in  which  strata 
were  deposited. 

The  alternation  x>f  marine  and  freshwater  formations,  both  on  a 
small  and  large  scale,  are  facts  well  ascertained  in  geology.  When 
it  occurs  on  a  small  scale,  it  may  have  arisen  from  the  alternate 
occupation  of  certain  spaces  by  river  water  and  the  sea ;  for  in  the 
flood  season  the  river  forces  back  the  ocean  and  freshens  it  over  a 
large  area,  depositing  at  the  same  time  its  sediment ;  after  which  the 
salt  water  again  returns,  and,  on  resuming  its  former  place,  brings 
with  it  sand,  mud,  and  marine  shells. 

*  See  Index  of  Principles,  "  Fossilization." 


CH.  IV.J  CONSOLIDATION   OP   STRATA.  33 

There  are  also  lagoons  at  the  mouths  of  many  rivers,  as  the  Nile 
and  Mississippi,  which  are  divided  off  by  bars  of  sand  from  the  sea, 
and  which  are  filled  with  salt  and  fresh  water  by  turns.  They  often 
communicate  exclusively  with  the  river  for  months,  years,  or  even 
centuries ;  and  then  a  breach  being  made  in  the  bar  of  sand,  they 
are  for  long  periods  filled  with  salt  water. 

The  Lym-Fiord  in  Jutland  offers  an  excellent  illustration  of 
analogous  changes ;  for,  in  the  course  of  the  last  thousand  years,  the 
western  extremity  of  this  long  frith,  which  is  120  miles  in  length, 
including  its  windings,  has  been  four  times  fresh  and  four  times  salt, 
a  bar  of  sand  between  it  and  the  ocean  having  been  as  often  formed 
and  removed.  The  last  irruption  of  salt  water  happened  in  1824, 
when  the  North  Sea  entered,  killing  all  the  freshwater  shells,  fish, 
and  plants ;  and  from  that  time  to  the  present,  the  sea-weed  Fucus 
vesiculosus,  together  with  oysters  and  other  marine  mollusca,  have 
succeeded  the  Cyclas,  Lymnea,  Paludina,  and  Chares.* 

But  changes  like  these  in  the  Lym-Fiord,  and  those  before  men- 
tioned as  occurring  at  the  mouths  of  great  rivers,  will  only  account 
for  some  cases  of  marine  deposits  of  partial  extent  resting  on  fresh- 
water strata.  When  we  find,  as  in  the  south-east  of  England,  a 
great  series  of  freshwater  beds,  1000  feet  in  thickness,  resting  upon 
marine  formations  and  again  covered  by  other  rocks,  such  as  the 
cretaceous,  more  than  1000  feet  thick,  and  of  deep-sea  origin,  we 
shall  find  it  necessary  to  seek  for  a  different  explanation  of  the  phe- 
nomena, f 


CHAPTER  IV. 

CONSOLIDATION  OF   STRATA  AND  PETRIFACTION  OF  FOSSILS. 

Chemical  and  mechanical  deposits — Cementing  together  of  particles — Hardening 
by  exposure  to  air — Concretionary  nodules — Consolidating  effects  of  pressure — 
Mineralization  of  organic  remains— Impressions  and  casts  how  formed — Fossil 
wood — Goppert's  experiments — Precipitation  of  stony  matter  most  rapid  where 
putrefaction  is  going  on — Source  of  lime  in  solution — Silex  derived  from  de- 
composition of  felspar — Proofs  of  the  lapidification  of  some  fossils  soon  after 
burial,  of  others  when  much  decayed. 

HAVING  spoken  in  the  preceding  chapters  of  the  characters  of  sedi- 
mentary formations,  both  as  dependent  on  the  deposition  of  inorganic 
matter  and  the  distribution  of  fossils,  I  may  next  treat  of  the  con- 
solidation of  stratified  rocks,  and  the  petrifaction  of  imbedded  or- 
ganic remains. 

Chemical  and  mechanical  deposits.  —  A  distinction  has  been  made 

*  See  Principles,  Index,  "  Lym-Fiord." 

f  See  below,  Chap.  XVIIL,  on  the  Wealden. 


34  CONSOLIDATION   OF    STRATA.  [Cn.  IV. 

by  geologists  between  deposits  of  a  chemical,  and  those  of  a  me- 
chanical, origin.  By  the  latter  name  are  designated  beds  of  mud, 
sand,  or  pebbles  produced  by  the  action  of  running  water,  also  ac- 
cumulations of  stones  and  scoriae  thrown  out  by  a  volcano,  which 
have  fallen  into  their  present  place  by  the  force  of  gravitation.  But 
the  matter  which  forms  a  chemical  deposit  has  not  been  mechanically 
suspended  in  water,  but  in  a  state  of  solution  until  separated  by 
chemical  action.  In  this  manner  carbonate  of  lime  is  often  precipi- 
tated upon  the  bottom  of  lakes  and  seas  in  a  solid  form,  as  may  be 
well  seen  in  many  parts  of  Italy,  where  mineral  springs  abound,  and 
where  the  calcareous  stone,  called  travertin,  is  deposited.  In  these 
springs  the  lime  is  usually  held  in  solution  by  an  excess  of  carbonic 
acid,  or  by  heat  if  it  be  a  hot  spring,  until  the  water,  on  issuing  from 
the  earth,  cools  or  loses  part  of  its  acid.  The  calcareous  matter  then 
falls  down  in  a  solid  state,  encrusting  shells,  fragments  of  wood  ami 
leaves,  and  binding  them  together.* 

In  coral  reefs,  large  masses  of  limestone  are  formed  by  the  stony 
skeletons  of  zoophytes ;  and  these,  together  with  shells,  become  ce- 
mented together  by  carbonate  of  lime,  part  of  which  is  probably 
furnished  to  the  sea  water  by  the  decomposition  of  dead  corals. 
Even  shells  of  which  the  animals  are  still  living,  on  these  reefs,  are 
very  commonly  found  to  be  encrusted  over  with  a  hard  coating  of 
limestone,  f 

If  sand  and  pebbles  are  carried  by  a  river  into  the  sea,  and  these 
are  bound  together  immediately  by  carbonate  of  lime,  the  deposit 
may  be  described  as  of  a  mixed  origin,  partly  chemical,  and  partly 
mechanical. 

Now,  the  remarks  already  made  in  Chapter  II.  on  the  original 
horizontality  of  strata  are  strictly  applicable  to  mechanical  deposits, 
and  only  partially  to  those  of  a  mixed  nature.  Such  as  are  purely 
chemical  may  be  formed  on  a  very  steep  slope,  or  may  even  encrust 
the  vertical  walls  of  a  fissure,  and  be  of  equal  thickness  throughout ; 
but  such  deposits  are  of  small  extent,  and  for  the  most  part  confined 
to  vein-stones. 

Cementing  of  particles.  —  It  is  chiefly  in  the  case  of  calcareous 
rocks  that  solidification  takes  place  at  the  time  of  deposition.  But 
there  are  many  deposits  in  which  a  cementing  process  comes  into 
operation  long  afterwards.  We  may  sometimes  observe,  where  the 
water  of  ferruginous  or  calcareous  springs  has  flowed  through  a  bed 
of  sand  or  gravel,  that  iron  or  carbonate  of  lime  has  been  deposited 
in  the  interstices  between  the  grains  or  pebbles,  so  that  in  certain 
places  the  whole  has  been  bound  together  into  a  stone,  the  same  set 
of  strata  remaining  in  other  parts  loose  and  incoherent. 

Proofs  of  a  similar  cementing  action  are  seen  in  a  rock  at  Kello- 
way  in  Wiltshire.  A  peculiar  band  of  sandy  strata  belonging  to  the 
group  called  Oolite  by  geologists,  may  be  traced  through  several 

*  See  Principles,  Index,  "  Calcareous  f  Ibid.  "  Travertin,"  "  Coral  Reefs," 
Springs,"  &c.  &c. 


CH.  IV.]  CONSOLIDATION   OF   STRATA.  35 

counties,  the  sand  being  for  the  most  part  loose  and  unconsolidated, 
but  becoming  stony  near  Kelloway.  In  this  district  there  are  nu- 
merous fossil  shells  which  have  decomposed,  having  for  the  most 
part  left  only  their  casts.  The  calcareous  matter  hence  derived  has 
evidently  served,  at  some  former  period,  as  a  cement  to  the  siliceous 
grains  of  sand,  and  thus  a  solid  sandstone  has  been  produced.  If  we 
take  fragments  of  many  other  argillaceous  grits,  retaining  the  casts 
of  shells,  and  plunge  them  into  dilute  muriatic  or  other  acid,  we  see 
them  immediately  changed  into  common  sand  and  mud ;  the  cement 
of  lime,  derived  from  the  shells,  having  been  dissolved  by  the  acid. 

Traces  of  impressions  and  casts  are  often  extremely  faint.  In 
some  loose  sands  of  recent  date  we  meet  with  shells  in  so  advanced 
a  stage  of  decomposition  as  to  crumble  into  powder  when  touched. 
It  is  clear  that  water  percolating  such  strata  may  soon  remove  the 
calcareous  matter  of  the  shell ;  and  unless  circumstances  cause  the 
carbonate  of  lime  to  be  again  deposited,  the  grains  of  sand  will  not 
be  cemented  together ;  in  which  case  no  memorial  of  the  fossil  will 
remain.  The  absence  of  organic  remains  from  many  aqueous  rocks 
may  be  thus  explained ;  but  we  may  presume  that  in  many  of  them 
no  fossils  were  ever  imbedded,  as  there  are  extensive  tracts  on  the 
bottoms  of  existing  seas  even  of  moderate  depth  on  which  no  frag" 
ment  of  shell,  coral,  or  other  living  creature  can  be  detected  by 
dredging.  On  the  other  hand,  there  are  depths  where  the  zero  of 
animal  life  has  been  approached ;  as,  for  example,  in  the  Mediter- 
ranean, at  the  depth  of  about  230  fathoms,  according  to  the  researches 
of  Prof.  E.  Forbes.  In  the  ./Egean  Sea  a  deposit  of  yellowish  mud 
of  a  very  uniform  character,  and  closely  resembling  chalk,  is  going 
on  in  regions  below  230  fathoms,  and  this  formation  must  be  wholly 
devoid  of  organic  remains.  * 

In  what  manner  silex  and  carbonate  of  lime  may  become  widely 
diffused  in  small  quantities  through  the  waters  which  permeate  the 
earth's  crust  will  be  spoken  of  presently,  when  the  petrifaction  of 
fossil  bodies  is  considered ;  but  I  may  remark  here  that  such  waters 
are  always  passing  in  the  case  of  thermal  springs  from  hotter  to 
colder  parts  of  the  interior  of  the  earth ;  and,  as  often  as  the  tem- 
perature of  the  solvent  is  lowered,  mineral  matter  has  a  tendency  to 
separate  from  it  and  solidify.  Thus  a  stony  cement  is  often  supplied 
to  sand,  pebbles,  or  any  fragmentary  mixture.  In  some  conglo- 
merates, like  the  pudding-stone  of  Hertfordshire  (a  Lower  Eocene 
deposit),  pebbles  of  flint  and  grains  of  sand  are  united  by  a  siliceous 
cement  so  firmly,  that  if  a  block  be  fractured  the  rent  passes  as  readily 
through  the  pebbles  as  through  the  cement. 

It  is  probable  that  many  strata  became  solid  at  the  time  when  they 
emerged  from  the  waters  in  which  they  were  deposited,  and  when 
they  first  formed  a  part  of  the  dry  land.  A  well-known  fact  seems 
to  confirm  this  idea :  by  far  the  greater  number  of  the  stones  used 
for  building  and  road-making  are  much  Softer  when  first  taken  from 

*  Report  Brit.  Ass.  1843,  p.  178. 
D  2 


36  CONSOLIDATION    OF    STRATA.  [<?H.  IV. 

the  quarry  than  after  they  have  been  long  exposed  to  the  air ;  and 
these,  when  once  dried,  may  afterwards  be  immersed  for  any  length 
of  time  in  water  without  becoming  soft  again.  Hence  it  is  found 
desirable  to  shape  the  stones  which  are  to  be  used  in  architecture 
while  they  are  yet  soft  and  wet,  and  while  they  contain  their 
"  quarry- water,"  as  it  is  called  ;  also  to  break  up  stone  intended  for 
roads  when  soft,  and  then  leave  it  to  dry  in  the  air  for  months  that 
it  may  harden.  Such  induration  may  perhaps  be  accounted  for  by 
supposing  the  water,  which  penetrates  the  minutest  pores  of  rocks, 
to  deposit,  on  evaporation,  carbonate  of  lime,  iron,  silex,  and  other 
minerals  previously  held  in  solution,  and  thereby  to  fill  up  the  pores 
partially.  These  particles,  on  crystallizing,  would  not  only  be  them- 
selves deprived  of  freedom  of  motion,  but  would  also  bind  together 
other  portions  of  the  rock  which  before  were  loosely  aggregated. 
On  the  same  principle  wet  sand  and  mud  become  as  hard  as  stone 
when  frozen  ;  because  one  ingredient  of  the  mass,  namely,  the  water, 
has  crystallized,  so  as  to  hold  firmly  together  all  the  separate  particles 
of  which  the  loose  mud  and  sand  were  composed. 

Dr.  MacCulloch  mentions  a  sandstone  in  Skye,  which  may  be 
moulded  like  dough  when  first  found;  and  some  simple  minerals, 
which  are  rigid  and  as  hard  as  glass  in  our  cabinets,  are  often  flexible 
and  soft  in  their  native  beds :  this  is  the  case  with  asbestos,  sahlite, 
tremolite,  and  chalcedony,  and  it  is  reported  also  to  happen  in  the 
case  of  the  beryl.  * 

The  marl  recently  deposited  at  the  bottom  of  Lake  Superior,  in 
North  America,  is  soft,  and  often  filled  with  freshwater  shells ;  but 
if  a  piece  be  taken  up  and  dried,  it  becomes  so  hard  that  it  can  only 
be  broken  by  a  smart  blow  of  the  hammer.  If  the  lake  therefore  was 
drained,  such  a  deposit  would  be  found  to  consist  of  strata  of  marl- 
stone,  like  that  observed  in  many  ancient  European  formations,  and 
like  them  containing  freshwater  shells. 

It  is  probable  that  some  of  the  heterogeneous  materials  which 
rivers  transport  to  the  sea  may  at  once  set  under  water,  like  the  arti- 
ficial mixture  called  pozzolana,  which  consists  of  fine  volcanic  sand 
charged  with  about  20  per  cent,  of  oxide  of  iron,  and  the  addition  of 
a  small  quantity  of  lime.  This  substance  hardens,  and  becomes  a 
solid  stone  in  water,  and  was  used  by  the  Romans  in  constructing 
the  foundations  of  buildings  in  the  sea. 

Consolidation  In  these  cases  is  brought  about  by  the  action  of 
chemical  affinity  on  finely  comminuted  matter  previously  suspended 
in  water.  After  deposition  similar  particles  seem  to  exert  a  mutual 
attraction  on  each  other,  and  congregate  together  in  particular  spots, 
forming  lumps,  nodules,  and  concretions.  Thus  in  many  argillaceous 
deposits  there  are  calcareous  balls,  or  spherical  concretions,  ranged 
in  layers  parallel  to  the  general  stratification  ;  an  arrangement  which 
took  place  after  the  shale  or  marl  had  been  thrown  down  in  succes- 
sive laminae ;  for  these  laminae  are  often  traced  in  the  concretions, 

*  Dr.  MacCulloch,  Syst.  of  GeoL  vol.  i.  p.  123. 


CH.  IV.] 


CONCRETIONARY   STRUCTURE. 


37 


Fig.  55. 


Calcareous  nodules  in  Lias. 


Fig.  56. 


remaining  parallel  to  those  of  the  surrounding  unconsolidated  rock. 

(See  fig.  55.)  Such  nodules  of  lime- 
stone have  often  a  shell  or  other  foreign 
body  in  the  centre.* 

Among  the  most  remarkable  ex- 
amples of  concretionary  structure  are 
those  described  by  Professor  Sedgwick 
as  abounding  in  the  magnesian  limestone  of  the  north  of  England. 
The  spherical  balls  are  of  various  sizes,  from  that  of  a  pea  to  a  dia- 
meter of  several  feet,  and  they  have  both  a  concentric  and  radiated 
structure,  while  at  the  same  time  the  laminae  of  original  deposition 
pass  uninterruptedly  through  them.  In  some  cliffs  this  limestone 
resembles  a  great  irregular  pile  of  cannon  balls.  Some  of  the  globular 
masses  have  their  centre  in  one  stratum,  while  a  portion  of  their 
exterior  passes  through  to  the  stratum  above  or  below.  Thus  the 
larger  spheroid  in  the  annexed  section  (fig.  56.)  passes  from  the  stratum 

b  upwards  into  a.  In  this  instance  we 
must  suppose  the  deposition  of  a  series 
of  minor  layers,  first  forming  the  stra- 
tum &,  and  afterwards  the  incumbent 
stratum  a ;  then  a  movement  of  the  par- 
ticles took  place,  and  the  carbonates  of 
lime  and  magnesia  separated  from  the 
more  impure  and  mixed  matter  forming  the  still  unconsolidated  parts 
of  the  stratum.  Crystallization,  beginning  at  the  centre,  must  hav^ 
gone  on  forming  concentric  coats  around  the  original  nucleus  without 
interfering  with  the  laminated  structure  of  the  rock. 

When  the  particles  of  rocks  have  been  thus  re-arranged  by  chemi- 
cal forces,  it  is  sometimes  difficult  or  impossible  to  ascertain  whether 
certain  lines  of  division  are  due  to  original  deposition  or  to  the  sub- 
sequent aggregation  of  similar  particles.  Thus  suppose  three  strata 
Fig-  57.  of  grit,  A,  B,  C,  are  charged  unequally 

with  calcareous  matter,  and  that  B  is  the 
e  most  calcareous.     If  consolidation  takes 
place  in  B,  the  concretionary  action  may 
spread  upwards  into  a  part  of  A,  where 


Spheroidal  concretions  in  magnesian 
limestone. 


BlU/ll 


IM 

'l  ll 


the  carbonate  of  lime  is  more  abundant  than  in  the  rest ;  so  that  a 
mass,  d,  e,  ft  forming  a  portion  of  the  superior  stratum,  becomes 
united  with  B  into  one  solid  mass  of  stone.  The  original  line  of 
division  d,  e,  being  thus  effaced,  the  line  d,  /,  would  generally  be 
considered  as  the  surface  of  the  bed  B,  though  not  strictly  a  true 
plane  of  stratification. 

Pressure  and  heat. — When  sand  and  mud  sink  to  the  bottom  of  a 
deep  sea,  the  particles  are  not  pressed  down  by  the  enormous  weight 
of  the  incumbent  ocean  ;  for  the  water,  which  becomes  mingled  with 
the  sand  and  mud,  resists  pressure  with  a  force  equal  to  that  of  the 
column  of  fluid  above.  The  same  happens  in  regard  to  organic  re- 

*  De  la  Beche,  Geol.  Researches,  p.  95.,  and  Geol.  Observer  (1851),  p.  686. 

D  3 


38  MINERALIZATION   OF  [Cn.  IV. 

mains  which  are  filled  with  water  under  great,  pressure  a  they  sink 
otherwise  they  would  be  immediately  crushed  to  pieces  and  flattened. 
Nevertheless,  if  the  materials  of  a  stratum  remain  in  a  yielding  state, 
and  do  not  set  or  solidify,  they  will  be  gradually  squeezed  down  by 
the  weight  of  other  materials  successively  heaped  upon  them,  just  as 
soft  clay  or  loose  sand  on  which  a  house  is  built  may  give  way.  By 
such  downward  pressure  particles  of  clay,  sand,  and  marl,  may  be- 
come packed  into  a  smaller  space,  and  be  made  to  cohere  together 
permanently. 

Analogous  effects  of  condensation  may  arise  when  the  solid  parts 
of  the  earth's  crust  are  forced  in  various  directions  by  those  me- 
chanical movements  afterwards  to  be  described,  by  which  strata  have 
been  bent,  broken,  and  raised  above  the  level  of  the  sea.  Rocks  of 
more  yielding  materials  must  often  have  been  forced  against  others 
previously  consolidated,  and,  thus  compressed,  may  have  acquired  a 
new  structure.  A  recent  discovery  may  help  us  to  comprehend  how 
fine  sediment  derived  from  the  detritus  of  rocks  may  be  solidified  by 
mere  pressure.  The  graphite  or  "  black  lead  "  of  commerce  having 
become  very  scarce,  Mr.  Brockedon  contrived  a  method  by  which  the 
dust  of  the  purer  portions  of  the  mineral  found  in  Borrowdale  might 
be  recomposed  into  a  mass  as  dense  and  compact  as  native  graphite. 
The  powder  of  graphite  is  first  carefully  prepared  and  freed  from  air, 
and  placed  under  a  powerful  press  on  a  strong  steel  die,  with  air-tight 
fittings.  It  is  then  struck  several  blows,  each  of  a  power  of  1000 
t^ns ;  after  which  operation  the  powder  is  so  perfectly  solidified  that 
it  can  be  cut  for  pencils,  and  exhibits  when  broken  the  same  texture 
as  native  graphite. 

But  the  action  of  heat  at  various  depths  in  the  earth  is  probably 
the  most  powerful  of  all  causes  in  hardening  sedimentary  strata.  To 
this  subject  I  shall  refer  again  when  treating  of  the  metamorphic 
rocks,  and  of  the  slaty  and  jointed  structure. 

Mineralization  of  organic  remains.  —  The  changes  which  fossil 
organic  bodies  have  undergone  since  they  were  first  imbedded  in 
rocks,  throw  much  light  on  the  consolidation  of  strata.  Fossil  shells 
in  some  modern  deposits  have  been  scarcely  altered  in  the  course  of 
centuries,  having  simply  lost  a  part  of  their  animal  matter.  But  in 
other  cases  the  shell  has  disappeared,  and  left  an  impression  only  of 
its  exterior,  or  a  cast  of  its  interior  form,  or  thirdly,  a  cast  of  the 
shell  itself,  the  original  matter  of  which  has  been  removed.  These 
different  forms  of  fossilization  may  easily  be  understood  if  we  examine 
the  mud  recently  thrown  out  from  a  pond  or  canal  in  which  there  aro 
shells.  If  the  mud  be  argillaceous,  it  acquires  consistency  on  drying, 
and  on  breaking  open  a  portion  of  it  we  find  that  each  shell  has  left 
impressions  of  its  external  form.  If  we  then  remove  the  shell  itself, 
we  find  within  a  solid  nucleus  of  clay,  having  the  form  of  the  interior 
of  the  shell.  This  form  is  often  very  different  from  that  of  the  outer 
shell.  Thus  a  cast  such  as  a,  fig.  58.,  commonly  called  a  fossil  screw, 
would  never  be  suspected  by  an  inexperienced  conchologist  to  be 
the  internal  shape  of  the  fossil  univalve,  b,  fig.  58.  Nor  should  we 


CH.  IV.]  ORGANIC   REMAINS.  39 

have  imagined  at  first  sight  that  the  shell  a  and  the  cast  b,  fig.  59., 
were  different  parts  of  the  same  fossil.     The  reader  will  observe,  in 


Fig.  58. 


Fig.  59. 


Phasianella  Heddingtonensis, 
and  cast  of  the  same.    Coral  Rag. 


Trochus  Anglicus,  and 
cast.    Lias. 


the  last-mentioned  figure  (6,  fig.  59.),  that  an  empty  space  shaded 
dark,  which  the  shell  itself  once  occupied,  now  intervenes  between 
the  enveloping  stone  and  the  cast  of  the  smooth  interior  of  the  whorls. 
Jn  such  cases  the  shell  has  been  dissolved  and  the  component  par- 
ticles removed  by  water  percolating  the  rock.  If  the  nucleus  were 
taken  out,  a  hollow  mould  would  remain,  on  which  the  external  form 
of  the  shell  with  its  tubercles  and  striae,  as  seen  in  a,  fig.  59.,  would 
be  seen  embossed.  Now  if  the  space  alluded  to  between  the  nucleus 
and  the  impression,  instead  of  being  left  empty,  has  been  filled  up 
with  calcareous  spar,  flint,  pyrites,  or  other  mineral,  we  then  obtain 
from  the  mould  an  exact  cast  both  of  the  external  and  internal  form 
of  the  original  shell.  In  this  manner  silicified  casts  of  shells  have 
been  formed ;  and  if  the  mud  or  sand  of  the  nucleus  happen  to  be 
incoherent,  or  soluble  in  acid,  we  can  then  procure  in  flint  an  empty 
shell,  which  in  shape  is  the  exact  counterpart  of  the  original.  This 
cast  may  be  compared  to  a  bronze  statue,  representing  merely  the 
superficial  form,  and  not  the  internal  organization ;  but  there  is 
another  description  of  petrifaction  by  no  means  uncommon,  and  of  a 
much  more  wonderful  kind,  which  may  be  compared  to  certain  ana- 
tomical models  in  wax,  where  not  only  the  outward  forms  and  fea- 
tures, but  the  nerves,  blood-vessels,  and  other  internal  organs  are  also 
shown.  Thus  we  find  corals,  originally  calcareous,  in  which  not  only 
the  general  shape,  but  also  the  minute  and  complicated  internal  or- 
ganization are  retained  in  flint. 

Such  a  process  of  petrifaction  is  still  more  remarkably  exhibited 
in  fossil  wood,  in  which  we  often  perceive  not  only  the  rings  of 
annual  growth,  but  all  the  minute  vessels  and  medullary  rays.  Many 
of  the  minute  pores  and  fibres  of  plants,  and  even  those  spiral  vessels 
which  in  the  living  vegetable  can  only  be  discovered  by  the  mi- 
croscope, are  preserved.  Among  many  instances,  I  may  mention  a 
fossil  tree,  72  feet  in  length,  found  at  Gosforth  near  Newcastle,  in 
sandstone  strata  associated  with  coal.  By  cutting  a  transverse  slice 
so  thin  as  to  transmit  light,  and  magnifying  it  about  fifty-five  times, 

D  4 


40  MINERALIZATION   OF  [Cn.  IV. 

the  texture  seen  in  fig.  60.  is  exhibited.  A  texture  equally  minute 
and  complicated  has  been  observed  in  the  wood 
r  !fcU*/*-jjua H*  °f  large  trunks  of  fossil  trees  found  in  the 
Craigleith  quarry  near  Edinburgh,  where  the 
stone  was  not  in  the  slightest  degree  siliceous, 
but  consisted  chiefly  of  carbonate  of  lime,  with 
oxide  of  iron,  alumina,  and  carbon.  The  pa- 
rallel rows  of  vessels  here  seen  are  the  rings 
of  annual  growth,  but  in  one  part  they  are  im- 

Texture  of  a  tree  from  the  coal  • 

strata,  magnified.  (Witham.)    perfectly  preserved,  the  wood  having  probably 

Transverse  section.  •   v   *  •  T    •  i_     i 

decayed  betore  the  mineralizing  matter  had 
penetrated  to  that  portion  of  the  tree. 

In  attempting  to  explain  the  process  of  petrifaction  in  such  cases, 
we  may  first  assume  that  strata  are  very  generally  permeated  by 
water  charged  with  minute  portions  of  calcareous,  siliceous,  and  other 
earths  in  solution.  In  what  manner  they  become  so  impregnated 
will  be  afterwards  considered.  If  an  organic  substance  is  exposed 
in  the  open  air  to  the  action  of  the  sun  and  rain,  it  will  in  time 
putrefy,  or  be  dissolved  into  its  component  elements,  which  consist 
chiefly  of  oxygen,  hydrogen,  and  carbon.  These  will  readily  be 
absorbed  by  the  atmosphere  or  be  washed  away  by  rain,  so  that  all 
vestiges  of  the  dead  animal  or  plant  disappear.  But  if  the  same 
substances  be  submerged  in  water,  they  decompose  more  gradually ; 
and  if  buried  in  earth,  still  more  slowly,  as  in  the  familiar  example 
of  wooden  piles  or  other  buried  timber.  Now,  if  as  fast  as  each 
particle  is  set  free  by  putrefaction  in  a  fluid  or  gaseous  state,  a 
particle  equally  minute  of  carbonate  of  lime,  flint,  or  other  mineral, 
is  at  hand  and  ready  to  be  precipitated,  we  may  imagine  this  in- 
organic matter  to  take  the  place  just  before  left  unoccupied  by  the 
organic  molecule.  In  this  manner  a  .cast  of  the  interior  of  certain 
vessels  may  first  be  taken,  and  afterwards  the  more  solid  walls  of  the 
same  may  decay  and  suffer  a  like  transmutation.  Yet  when  the 
whole  is  lapidified,  it  may  not  form  one  homogeneous  mass  of  stone 
or  metal.  Some  of  the  original  ligneous,  osseous,  or  other  organic 
elements  may  remain  mingled  in  certain  parts,  or  the  lapidifying 
substance  itself  may  be  differently  coloured  at  different  times,  or  so 
crystallized  as  to  reflect  light  differently,  and  thus  the  texture  of  the 
original  body  may  be  faithfully  exhibited. 

The  student  may  perhaps  ask  whether,  on  chemical  principles,  we 
have  any  ground  to  expect  that  mineral  matter  will  be  thrown  down 
precisely  in  those  spots  where  organic  decomposition  is  in  progress  ? 
The  following  curious  experiments  may  serve  to  illustrate  this  point. 
Professor  Goppert  of  Breslau  attempted  recently  to  imitate  the  na- 
tural process  of  petrifaction.  For  this  purpose  he  steeped  a  variety 
of  animal  and  vegetable  substances  in  waters,  some  holding  siliceous, 
others  calcareous,  others  metallic  matter  in  solution.  He  found  that 
in  the  period  of  a  few  weeks,  or  even  days,  the  organic  bodies  thus 
immersed  were  mineralized  to  a  certain  extent.  Thus,  for  example, 
thin  vertical  slices  of  deal,  taken  from  the  Scotch  fir  (Pinus  syl- 


CH.  IV.  1  ORGANIC   REMAINS.  41 

vestris),  were  immersed  in  a  moderately  strong  solution  of  sulphate 
of  iron.  When  they  had  been  thoroughly  soaked  in  the  liquid  for 
several  days  they  were  dried  and  exposed  to  a  red-heat  until  the 
vegetable  matter  was  burnt  up  and  nothing  remained  but  an  oxide  of 
iron,  which  was  found  to  have  taken  the  form  of  the  deal  so  exactly 
that  casts  even  of  the  dotted  vessels  peculiar  to  this  family  of  plants 
were  distinctly  visible  under  the  microscope. 

Another  accidental  experiment  has  been  recorded  by  Mr.  Pepys  in 
the  Geological  Transactions.  *  An  earthen  pitcher  containing  several 
quarts  of  sulphate  of  iron  had  remained  undisturbed  and  unnoticed 
for  about  a  twelvemonth  in  the  laboratory.  At  the  end  of  this  time 
when  the  liquor  was  examined  an  oily  appearance  was  observed  on 
the  surface,  and  a  yellowish  powder,  which  proved  to  be  sulphur, 
together  with  a  quantity  of  small  hairs.  At  the  bottom  were  dis- 
covered the  bones  of  several  mice  in  a  sediment  consisting  of  small 
grains  of  pyrites,  others  of  sulphur,  others  of  crystallized  green  sul- 
phate of  iron,  and  a  black  muddy  oxide  of  iron.  It  was  evident  that 
some  mice  had  accidentally  been  drowned  in  the  fluid,  and  by  the 
mutual  action  of  the  animal  matter  and  the  sulphate  of  iron  on  each 
other,  the  metallic  sulphate  had  been  deprived  of  its  oxygen ;  hence 
the  pyrites  and  the  other  compounds  were  thrown  down.  Although 
the  mice  were  not  mineralized,  or  turned  into  pyrites,  the  pheno- 
menon shows  how  mineral  waters,  charged  with  sulphate  of  iron, 
may  be  deoxydated  on  coming  in  contact  with  animal  matter  under- 
going putrefaction,  so  that  atom  after  atom  of  pyrites  may  be  pre- 
cipitated, and  ready,  under  favourable  circumstances,  to  replace  the 
oxygen,  hydrogen,  and  carbon  into  which  the  original  body  would  be 
resolved. 

The  late  Dr.  Turner  observes,  that  when  mineral  matter  is  in  a 
"  nascent  state,"  that  is  to  say,  just  liberated  from  a  previous  state  of 
chemical  combination,  it  is  most  ready  to  unite  with  other  matter, 
and  form  a  new  chemical  compound.  Probably  the  particles  or  atoms 
just  set  free  are  of  extreme  minuteness,  and  therefore  move  more 
freely,  and  are  more  ready  to  obey  any  impulse  of  chemical  affinity. 
Whatever  be  the  cause,  it  clearly  follows,  as  before  stated,  that  where 
organic  matter  newly  imbedded  in  sediment  is  decomposing,  there 
will  chemical  changes  take  place  most  actively. 

An  analysis  was  lately  made  of  the  water  which  was  flowing  off 
from  the  rich  mud  deposited  by  the  Hooghly  river  in  the  Delta  of 
the  Ganges  after  the  annual  inundation.  This  water  was  found  to 
be  highly  charged  with  carbonic  acid  gas  holding  lime  in  solution,  f 
Now  if  newly-deposited  mud  is  thus  proved  to  be  permeated  by 
mineral  matter  in  a  state  of  solution,  it  is  not  difficult  to  perceive 
that  decomposing  organic  bodies,  naturally  imbedded  in  sediment, 
may  as  readily  become  petrified  as  the  substances  artificially  im- 
mersed by  Professor  Goppert  in  various  fluid  mixtures. 

*  Vol.  i.  p.  399.  first  series. 

f  Piddington,  Asiat.  Kesearch.  vol.  xviii.  p.  226. 


42  FLINT   OP    SILICIFIED   FOSSILS.  [Cn.  IV. 

It  is  well  known  that  the  water  of  springs,  or  that  which  is 
continually  percolating  the  earth's  crust,  is  rarely  free  from  a  slight 
admixture  either  of  iron,  carbonate  of  lime,  sulphur,  silica,  potash,  or 
some  other  earthy,  alkaline,  or  metallic  ingredient.  Hot  springs  in 
particular  are  copiously  charged  with  one  or  more  of  these  elements  ; 
and  it  is  only  in  their  waters  that  silex  is  found  in  abundance.  In 
certain  cases,  therefore,  especially  in  volcanic  regions,  we  may  imagine 
the  flint  of  silicified  wood  and  corals  to  have  been  supplied  by  the 
waters  of  thermal  springs.  In  other  instances,  as  in  tripoli,  it  may 
have  been  derived  in  great  part,  if  not  wholly,  from  the  decomposi- 
tion of  diatomacese,  sponges,  and  other  bodies.  But  even  if  this  be 
granted,  we  have  still  to  inquire  whence  a  lake  or  the  ocean  can  be 
constantly  replenished  with  the  calcareous  and  siliceous  matter  so 
abundantly  withdrawn  from  it  by  the  secretions  of  living  beings. 

In  regard  to  carbonate  of  lime  there  is  no  difficulty,  because 
not  only  are  calcareous  springs  very  numerous,  but  even  rain- 
water, when  it  falls  on  ground  where  vegetable  matter  is  decom- 
posing, may  become  so  charged  with  carbonic  acid  as  to  acquire  a 
power  of  dissolving  a  minute  portion  of  the  calcareous  rocks  over 
which  it  flows.  Hence  marine  corals  and  mollusca  may  be  provided 
by  rivers  with  the  materials  of  their  shells  and  solid  supports.  But 
pure  silex,  even  when  reduced  to  the  finest  powder  and  boiled,  is 
insoluble  in  water,  except  at  very  high  temperatures.  Nevertheless, 
Dr.  Turner  has  well  explained,  in  an  essay  on  the  chemistry  of 
geology  *,  how  the  decomposition  of  felspar  may  be  a  source  of  silex 
in  solution.  He  has  remarked  that  the  siliceous  earth,  which  con- 
stitutes more  than  half  the  bulk  of  felspar,  is  intimately  combined 
with  alumine,  potash,  and  some  other  elements.  The  alkaline  matter 
of  the  felspar  has  a  chemical  affinity  for  water,  as  also  for  the  car- 
bonic acid  which  is  more  or  less  contained  in  the  waters  of  most 
springs.  The  water  therefore  carries  away  alkaline  matter,  and 
leaves  behind  a  clay  consisting  of  alumine  and  silica.  But  this  re- 
sidue of  the  decomposed  mineral,  which  in  its  purest  state  is  called 
porcelain  clay,  is  found  to  contain  a  part  only  of  the  silica  which 
existed  in  the  original  felspar.  The  other  part,  therefore,  must  have 
been  dissolved  and  removed :  and  this  can  be  accounted  for  in  .two 
ways ;  first,  because  silica  when  combined  with  an  alkali  is  soluble 
in  water ;  secondly,  because  silica,  in  what  is  technically  called  its 
nascent  state,  is  also  soluble  in  water.  Hence  an  endless  supply  of 
silica  is  afforded  to  rivers  and  the  waters  of  the  sea.  For  the  fel- 
spathic  rocks  are  universally  distributed,  constituting,  as  they  do, 
so  large  a  proportion  of  the  volcanic,  plutonic,  and  metamorphic  for- 
mations. Even  where  they  chance  to  be  absent  in  mass,  they  rarely 
fail  to  occur  in  the  superficial  gravel  or  alluvial  deposits  of  the  basin 
of  every  large  river. 

The  disintegration  of  mica  also,  another  mineral  which  enters 
largely  into  the  composition  of  granite  and  various  sandstones,  may 

*  Jam.  Ed.  New  Phil.  Journ.  No.  30.  p.  246. 


CH.  IV.]  PROCESS   OF   PETRIFACTION.  43 

yield  silica  which  may  be  dissolved  in  water,  for  nearly  half  of  this 
mineral  consists  of  silica,  combined  with  alumine,  potash,  and  about 
a  tenth  part  of  iron.  The  oxidation  of  this  iron  in  the  air  is  the 
principal  cause  of  the  waste  of  mica. 

We  have  still,  however,  much  to  learn  before  the  conversion  of 
fossil  bodies  into  stone  is  fully  understood.  Some  phenomena  seem 
to  imply  that  the  mineralization  must  proceed  with  considerable 
rapidity,  for  stems  of  a  soft  and  succulent  character,  and  of  a  most 
perishable  nature,  are  preserved  in  flint ;  and  there  are  instances  of  the 
complete  silicifi  cation  of  the  young  leaves  of  a  palm-tree  when  just 
about  to  shoot  forth,  and  in  that  state  which  in  the  West  Indies  is 
called  the  cabbage  of  the  palm.*  It  may,  however,  be  questioned 
whether  in  such  cases  there  may  not  have  been  some  antiseptic  quality 
in  the  water  which  retarded  putrefaction,  so  that  the  soft  parts  of  the 
buried  substance  may  have  remained  for  a  long  time  without  disin- 
tegration, like  the  flesh  of  bodies  imbedded  in  peat. 

Mr.  Stokes  has  pointed  out  examples  of  petrifactions  in  which  the 
more  perishable,  and  others  where  the  more  durable,  portions  of  wood 
are  preserved.  These  variations,  he  suggests,  must  doubtless  have 
depended  on  the  time  when  the  lapidifying  mineral  was  introduced. 
Thus,  in  certain  silicified  stems  of  palm-trees,  the  cellular  tissue,  that 
most  destructible  part,  is  in  good  condition,  while  all  signs  of  the 
hard  woody  fibre  have  disappeared,  the  spaces  once  occupied  by  it 
being  hollow  or  filled  with  agate.  Here,  petrifaction  must  have  com- 
menced soon  after  the  wood  was  exposed  to  the  action  of  moisture, 
and  the  supply  of  mineral  matter  must  then  have  failed,  or  the  water 
must  have  become  too  much  diluted  before  the  woody  fibre  decayed. 
But  when  this  fibre  is  alone  discoverable,  we  must  suppose  that  an 
interval  of  time  elapsed  before  the  commencement  of  lapidification, 
during  which  the  cellular  tissue  was  obliterated.  When  both  struc- 
tures, namely,  the  cellular  and  the  woody  fibre,  are  preserved,  the 
process  must  have  commenced  at  an  early  period,  and  continued 
without  interruption  till  it  was  completed  throughout.! 

*  Stokes,  Geol.  Trans.,  vol.  v.  p.  212.  second  series.  f  Ibid. 


44  LAND   HAS   BEEN  RAISED,  [Cn.  V. 


CHAPTER  V. 

ELEVATION   OF    STRATA  ABOVE   THE    SEA  —  HORIZONTAL  AND  INCLINED 
STRATIFICATION. 

Why  the  position  of  marine  strata,  above  the  level  of  the  sea,  should  be  referred  to 
the  rising  up  of  the  land,  not  to  the  going  down  of  the  sea — Upheaval  of  exten- 
sive masses  of  horizontal  strata — Inclined  and  vertical  stratification — Anticlinal 
and  synclinal  lines — Bent  strata  in  east  of  Scotland — Theory  of  folding  by 
lateral  movement — Creeps — Dip  and  strike — Structure  of  the  Jura — Various 
forms  of  outcrop — Rocks  broken  by  flexure  —  Inverted  position  of  disturbed 
strata — Unconformable  stratification  —  Hutton  and  Playfair  on  the  same — 
Fractures  of  strata — Polished  surfaces — Faults — Appearance  of  repeated  alter- 
nations produced  by  them — Origin  of  great  faults. 

LAND  has  been  raised,  not  the  sea  lowered. — It  has  been  already 
stated  that  the  aqueous  rocks  containing  marine  fossils  extend  over 
wide  continental  tracts,  and  are  seen  in  mountain  chains  rising  to 
great  heights  above  the  level  of  the  sea  (p.  4.).  Hence  it  follows,  that 
what  is  now  dry  land  was  once  under  water.  But  if  we  admit  this 
conclusion,  we  must  imagine,  either  that  there  has  been  a  general 
lowering  of  the  waters  of  the  ocean,  or  that  the  solid  rocks,  once  covered 
by  water,  have  been  raised  up  bodily  out  of  the  sea,  and  have  thus 
become  dry  land.  The  earlier  geologists,  finding  themselves  reduced 
to  this  alternative,  embraced  the  former  opinion,  assuming  that  the 
ocean  was  originally  universal,  and  had  gradually  sunk  down  to  its 
actual  level,  so  that  the  present  islands  and  continents  were  left  dry. 
It  seemed  to  them  far  easier  to  conceive  that  the  water  had  gone 
down,  than  that  solid  land  had  risen  upwards  into  its  present  position. 
It  was,  however,  impossible  to  invent  any  satisfactory  hypothesis  to 
explain  the  disappearance  of  so  enormous  a  body  of  water  throughout 
the  globe,  it  being  necessary  to  infer  that  the  ocean  had  once  stood 
at  whatever  height  marine  shells  might  be  detected.  It  moreover 
appeared  clear,  as  the  science  of  Geology  advanced,  that  certain  spaces 
on  the  globe  had  been  alternately  sea,  then  land,  then  estuary,  then 
sea  again,  and,  lastly,  once  more  habitable  land,  having  remained  in 
each  of  these  states  for  considerable  periods.  In  order  to  account  for 
such  phenomena,  without  admitting  any  movement  of  the  land  itself, 
we  are  required  to  imagine  several  retreats  and  returns  of  the  ocean ; 
and  even  then  our  theory  applies  merely  to  cases  where  the  marine 
strata  composing  the  dry  land  are  horizontal,  leaving  unexplained 
those  more  common  instances  where  strata  are  inclined,  curved,  or 
placed  on  their  edges,  and  evidently  not  in  the  position  in  which  they 
were  first  deposited. 

Geologists,  therefore,  were  at  last  compelled  to  have  recourse  to 
the  other  alternative,  namely,  the  doctrine  that  the  solid  land  has 
been  repeatedly  moved  upwards  or  downwards,  so  as  permanently  to 
change  its  position  relatively  to  the  sea.  There  are  several  distinct 


CH.  V.]  NOT   THE   SEA   LOWERED.  45 

grounds  for  preferring  this  conclusion.  First,  it  will  account  equally 
for  the  position  of  those  elevated  masses  of  marine  origin  in  which 
the  stratification  remains  horizontal,  and  for  those  in  which  the  strata 
are  disturbed,  broken,  inclined,  or  vertical.  Secondly,  it  is  consistent 
with  human  experience  that  land  should  rise  gradually  in  some  places 
and  be  depressed  in  others.  Such  changes  have  actually  occurred  in 
our  own  days,  and  are  now  in  progress,  having  been  accompanied  in 
some  cases  by  violent  convulsions,  while  in  others  they  have  pro- 
ceeded so  insensibly,  as  to  have  been  ascertainable  only  by  the  most 
careful  scientific  observations,  made  at  considerable  intervals  of  time. 
On  the  other  hand,  there  is  no  evidence  from  human  experience  of 
a  lowering  of  the  sea's  level  in  any  region,  and  the  ocean  cannot  sink 
in  one  place  without  its  level  being  depressed  all  over  the  globe. 

These  preliminary  remarks  will  prepare  the  reader  to  understand 
the  great  theoretical  interest  attached  to  all  facts  connected  with  the 
position  of  strata,  whether  horizontal  or  inclined,  curved  or  vertical. 

Now  the  first  and  most  simple  appearance  is  where  strata  of 
marine  origin  occur  above  the  level  of  the  sea  in  horizontal  position. 
Such  are  the  strata  which  we  meet  with  in  the  south  of  Sicily,  filled 
with  shells  for  the  most  part  of  the  same  species  as  those  now  living 
in  the  Mediterranean.  Some  of  these  rocks  rise  to  the  height  of 
more  than  2000  feet  above  the  sea.  Other  mountain  masses  might 
be  mentioned,  composed  of  horizontal  strata  of  high  antiquity,  which 
contain  fossil  remains  of  animals  wholly  dissimilar  from  any  now 
known  to  exist.  In  the  south  of  Sweden,  for  example,  near  Lake 
Wener,  the  beds  of  one  of  the  oldest  of  the  fossiliferous  deposits, 
namely  that  formerly  called  Transition,  and  now  Silurian,  by  geo- 
logists, occur  in  as  level  a  position  as  if  they  had  recently  formed 
part  of  the  delta  of  a  great  river,  and  been  left  dry  on  the  retiring  of 
the  annual  floods.  Aqueous  rocks  of  about  the  same  age  extend  for 
hundreds  of  miles  over  the  lake-district  of  North  America,  and  exhibit 
in  like  manner  a  stratification  nearly  undisturbed.  The  Table  Moun- 
tain at  the  Cape  of  Good  Hope  is  another  example  of  highly  elevated 
yet  perfectly  horizontal  strata,  no  less  than  3500  feet  in  thickness, 
and  consisting  of  sandstone  of  very  ancient  date. 

Instead  of  imagining  that  such  fossiliferous  rocks  were  always  at 
their  present  level,  and  that  the  sea  was  once  high  enough  to  cover 
them,  we  suppose  them  to  have  constituted  the  ancient  bed  of  the 
ocean,  and  that  they  were  gradually  uplifted  to  their  present  height. 
This  idea,  however  startling  it  may  at  first  appear,  is  quite  in 
accordance,  as  before  stated,  with  the  analogy  of  changes  now  going 
on  in  certain  regions  of  the  globe.  Thus,  in  parts  of  Sweden,  and 
the  shores  and  islands  of  the  Gulf  of  Bothnia,  proofs  have  been 
obtained  that  the  land  is  experiencing,  and  has  experienced  for 
centuries,  a  slow  upheaving  movement.  Playfair  argued  in  favour 
of  this  opinion  in  1802 ;  and  in  1807,  Von  Buch,  after  his  travels  in 
Scandinavia,  announced  his  conviction  that  a  rising  of  the  land  was 
in  progress.  Celsius  and  other  Swedish  writers  had,  a  century 
before,  declared  their  belief  that  a  gradual  change  had,  for  ages, 


46  EISING   AND    SINKING   OP   LAND.  [Cm  V. 

been  taking  place  in  the  relative  level  of  land  and  sea.  They  attri- 
buted the  change  to  a  fall  of  the  waters  both  of  the  ocean  and  the 
Baltic.  This  theory,  however,  has  now  been  refuted  by  abundant 
evidence ;  for  the  alteration  of  relative  level  has  neither  been 
universal  nor  everywhere  uniform  in  quantity,  but  has  amounted, 
in  some  regions,  to  several  feet  in  a  century,  in  others  to  a  few 
inches ;  while  in  the  southernmost  part  of  Sweden,  or  the  province 
of  Scania,  there  has  been  actually  a  loss  instead  of  a  gain  of  land, 
buildings  having  gradually  sunk  below  the  level  of  the  sea.* 

It  appears,  from  the  observations  of  Mr.  Darwin  and  others,  that 
very  extensive  regions  of  the  continent  of  South  America  have  been 
undergoing  slow  and  gradual  upheaval,  by  which  the  level  plains  of 
Patagonia,  covered  with  recent  marine  shells,  and  the  Pampas  of 
Buenos  Ayres,  have  been  raised  above  the  level  of  the  sea.f  On  the 
other  hand,  the  gradual  sinking  of  the  west  coast  of  Greenland,  for 
the  space  of  more  than  600  miles  from  north  to  south,  during  the 
last  four  centuries,  has  been  established  by  the  observations  of  a 
Danish  naturalist,  Dr.  Pingel.  And  while  these  proofs  of  continental 
elevation  and  subsidence,  by  slow  and  insensible  movements,  have 
been  recently  brought  to  light,  the  evidence  has  been  daily  strength- 
ened of  continued  changes  of  level  effected  by  violent  convulsions 
in  countries  where  earthquakes  are  frequent.  There  the  rocks  are 
rent  from  time  to  time,  and  heaved  up  or  thrown  down  several  feet 
at  once,  and  disturbed  in  such  a  manner,  that  the  original  position  of 
strata  may,  in  the  course  of  centuries,  be  modified  to  any  amount. 

It  has  also  been  shown  by  Mr.  Darwin,  that,  in  those  seas  where 
circular  coral  islands  and  barrier  reefs  abound,  there  is  a  slow  and 
continued  sinking  of  the  submarine  mountains  on  which  the  masses 
of  coral  are  based ;  while  there  are  other  areas  of  the  South  Sea, 
where  the  land  is  on  the  rise,  and  where  coral  has  been  upheaved  far 
above  the  sea-level. 

It  would  require  a  volume  to  explain  to  the  reader  the  various 
facts  which  establish  the  reality  of  these  movements  of  land,  whether 
of  elevation  or  depression,  whether  accompanied  by  earthquakes  or 
accomplished  slowly  and  without  local  disturbance.  Having  treated 
fully  of  these  subjects  in  the  Principles  of  Geology  J,  I  shall  assume, 
in  the  present  work,  that  such  changes  are  part  of  the  actual  course 
of  nature ;  and  when  admitted,  they  will  be  found  to  afford  a  key  to 
the  interpretation  of  a  variety  of  geological  appearances,  such  as  the 
elevation  of  horizontal,  inclined,  or  disturbed  marine  strata,  and  the 
superposition  of  freshwater  to  marine  deposits,  afterwards  to  be 
described.  It  will  also  appear,  in  the  sequel,  how  much  light  the 

*  In   the  first  three  editions  of  my  opinion  in  the  Phil.  Trans.  1835,  Part  I. 

Principles  of  Geology,  I  expressed  many  See  also  the  Principles,  4th  and  subse- 

doubts  as  to  the  validity  of  the  alleged  quent  editions. 

proofs   of   a  gradual  rise  of   land    in  f  See  his  Journal  of  a  Naturalist  in 

Sweden  ;  but  after  visiting  that  country,  Voyage  of  the  Beagle,  and  his  work  on 

in  1834, 1  retracted  these  objections,  and  Coral  Reefs.* 

published   a  detailed  statement  of  the  J  See  chaps,  xxvii.  to  xxxii.  inclusive, 

observations  which  led  me  to  alter  my  and  chap.  1. 


CH.  V.] 


INCLINED   STRATIFICATION. 


47 


Fig.  61. 


doctrine  of  a  continued  subsidence  of  land  may  throw  on  the  manner 
in  which  a  series  of  strata,  formed  in  shallow  water,  may  have  accu- 
mulated to  a  great  thickness.  The  excavation  of  valleys  also,  and 
other  effects  of  denudation,  of  which  I  shall  presently  treat,  can  alone 
be  understood  when  we  duly  appreciate  the  proofs,  now  on  record, 
of  the  prolonged  rising  and  sinking  of  land,  throughout  wide  areas. 

To  conclude  this  subject,  I  may  remind  the  reader,  that  were  we 
to  embrace  the  doctrine  which  ascribes  the  elevated  position  of  marine 
formations,  and  the  depression  of  certain  freshwater  strata,  to  oscil- 
lations in  the  level  of  the  waters  instead  of  the  land,  we  should  be 
compelled  to  admit  that  the  ocean  has  been  sometimes  every  where 
much  shallower  than  at  present,  and  at  others  more  than  three  miles 
deeper. 

Inclined  stratification.  —  The  most  unequivocal  evidence  of  a 
change  in  the  original  position  of  strata  is  afforded  by  their  standing 
up  perpendicularly  on  their  edges,  which  is  by  no  means  a  rare 
phenomenon,  especially  in  mountainous  countries.  Thus  we  find  in 
Scotland,  on  the  southern  skirts  of  the  Grampians,  beds  of  pudding- 
stone  alternating  with  thin  layers  of  fine  sand,  all  placed  vertically 
to  the  horizon.  When  Saussure  first  ob- 
served certain  conglomerates  in  a  simi- 
lar position  in  the  Swiss  Alps,  he  re- 
marked that  the  pebbles,  being  for  the 
most  part  of  an  oval  shape,  had  their 
longer  axes  parallel  to  the  planes  of 
stratification  (see  fig.  61.).  From  this 
he  inferred,  that  such  strata  must,  at 

first,     have    been     horizontal,     each     OVal     Vertical  conglomerate  and  sandstone. 

pebble  having  originally  settled  at  the  bottom  of  the  water,  with  its 
flatter  side  parallel  to  the  horizon,  for  the  same  reason  that  an  egg 
will  not  stand  on  either  end  if  unsupported.  Some  few,  indeed,  of 
the  rounded  stones  in  a  conglomerate  occasionally  afford  an  exception 
to  the  above  rule,  for  the  same  reason  that  we  see  on  a  shingle  beach 
some  oval  or  flat-sided  pebbles  resting  on  their  ends  or  edges  ;  these 
having  been  forced  along  the  bottom  and  against  each  other  by  a 
wave  or  current  so  as  to  settle  in  this  position. 

Vertical  strata,  when  they  can  be  traced  continuously  upwards  or 
downwards  for  some  depth,  are  almost  invariably  seen  to  be  parts  of 
great  curves,  which  may  have  a  diameter  of  a  few  yards,  or  of  several 
miles.  I  shall  first  describe  two  curves  of  considerable  regularity, 
which  occur  in  Forfarshire,  extending  over  a  country  twenty  miles  in 
breadth,  from  the  foot  of  the  Grampians  to  the  sea  near  Arbroath. 

The  mass  of  strata  here  shown  may  be  nearly  2000  feet  in  thick- 
ness, consisting  of  red  and  white  sandstone,  and  various  coloured 
shales,  the  beds  being  distinguishable  into  four  principal  groups, 
namely,  No.  1.  red  marl  or  shale;  No.  2.  red  sandstone,  used  for 
building ;  No.  3.  conglomerate ;  and  No.  4.  grey  paving-stone,  and 
tile-stone,  with  green  and  reddish  shale,  containing  peculiar  organic 
remains.  A  glance  at  the  section  will  show  that  each  of  the  forma- 


48  CURVED   STRATA.  [Cn.  V. 

tions  2,  3,  4,  are  repeated  thrice  at  the 
surface,  twice  with  a  southerly,  and  once 
with  a  northerly  inclination  or  dip,  and 
the   beds  in  No.   1.,   which   are  nearly 
horizontal,  are  still  brought  up  twice  by 
a  slight  curvature  to  the  surface,  once 
on  each  side  of  A.     Beginning   at  the 
north-west  extremity,  the  tile-stones  and 
conglomerates  No.  4.  and  No.  3.  are  ver- 
tical, and  they  generally  form  a  ridge 
parallel  to   the   southern   skirts    of  the 
Grampians.     The  superior  strata  Nos.  2. 
and  J .  become  less  and  less  inclined  on 
descending  to  the  valley  of  Strathmore, 
where    the    strata,    having    a    concave 
bend,,  are   said   by  geologists   to   lie   in 
a  "trough"  or  "basin."     Through   the 
centre  of  this  valley  runs  an  imaginary 
line   A,  called   technically  a  "synclinal 
line,"  where  the  beds,  which  are  tilted 
J   in  opposite  directions,  may  be  supposed 
to  meet.     It  is  most  important  for  the 
observer  to  mark  such  lines,  for  he  will 
perceive  by  the  diagram,  that  in  travel- 
ling from  the  north  to  the  centre  of  the 
basin,  he  is  always  passing  from  older 
to  newer  beds ;  whereas,  after  crossing 
the  line  A,  and  pursuing  his  course  in 
the  same  southerly  direction,  he  is  con- 
tinually leaving  the  newer,  and  advanc- 
ing upon  older  strata.     All  the  deposits 
which   he  had    before    examined   begin 
then  to  recur  in  reversed  order,  until  he 
arrives  at  the  central  axis  of  the  Sidlaw 
hills,  where  the  strata  are  seen  to  form 
an  arch  or  saddle,  having  an  anticlinal 
line  B,  in  the  centre.     On  passing  this 
line,  and  continuing  towards  the  S.  E.,  the  formations  4,  3,  and  2,  are 
again  repeated,  in  the  same  relative  order  of  superposition,  but  with 
a  southerly  dip.     At  Whiteness  (see  diagram)  it  will  be  seen  that  the 
inclined  strata  are  covered  by  a  newer  deposit,  a,  in  horizontal  beds. 
These  are  composed  of  red  conglomerate  and  sand,  and  are  newer 
than  any  of  the  groups,  1,  2,  3,  4,  before  described,  and  rest  uncon- 
formabty  upon  strata  of  the  sandstone  group,  No.  2. 

An  example  of  curved  strata,  in  which  the  bends  or  convolutions 
of  the  rock  are  sharper  and  far  more  numerous  within  an  equal  space, 
has  been  well  described  by  Sir  James  Hall.*  It  occurs  near  St. 


*  Edin.  Trans,  vol.  vii.  pi  3. 


CH.  V.]     EXPERIMENTS  TO  ILLUSTRATE  CURVED  STRATA.        49 

Abb's  Head,  on  the  east  coast  of  Scotland,  where  the  rocks  consist 
principally  of  a  bluish  slate,  having  frequently  a  ripple-marked  sur- 
face. The  undulations  of  the  beds  reach  from  the  top  to  the  bottom 

Fig.  63. 


Curved  strata  of  slate  near  St.  Abb's  Head,  Berwickshire.    ( Sir  J.  Hall.) 

of  cliffs  from  200  to  300  feet  in  height,  and  there  are  sixteen  distinct 
bendings  in  the  course  of  about  six  miles,  the  curvatures  being  alter- 
nately concave  and  convex  upwards. 

An  experiment  was  made  by  Sir  James  Hall,  with  a  view  of  illus- 
trating the  manner  in  which  such  strata,  assuming  them  to  have  been 
originally  horizontal,  may  have  been  forced  into  their  present  position. 
A  set  of  layers  of  clay  were  placed  under  a  weight,  and  their  oppo- 
site ends  pressed  towards  each  other  with  such  force  as  to  cause  them 
to  approach  more  nearly  together.  On  the  removal  of  the  weight, 
the  layers  of  clay  were  found  to  be  curved  and  folded,  so  as  to  bear 
a  miniature  resemblance  to  the  strata  in  the  cliffs.  We  must,  how- 
ever, bear  in  mind,  that  in  the  natural  section  or  sea-cliff  we  only 
see  the  foldings  imperfectly,  one  part  being  invisible  beneath  the 
sea,  and  the  other,  or  upper  portion,  being  supposed  to  have  been 
carried  away  by  denudation,  or  that  action  of  water  which  will  be 

Fig.  64. 


explained  in  the  next  chapter.  The  dark  lines  in  the  accompanying 
plan  (fig.  64.)  represent  what  is  actually  seen  of  the  strata  in  part  of 
the  line  of  cliff  alluded  to ;  the  fainter  lines,  that  portion  which  is 


50  CURVED    STRATA.  [Cn.  V. 

concealed  beneath  the  sea  level,  as  also  that  which  is  supposed  to 
have  once  existed  above  the  present  surface. 

We  may  still  more  easily  illustrate  the  effects  which  a  lateral  thrust 
might  produce  on  flexible  strata,  by  placing  several  pieces  of  differ- 
ently coloured  cloths  upon  a  table,  and  when  they  are  spread  out  hori- 

Fig.  65. 


zontally,  cover  them  with  a  book.  Then  apply  other  books  to  each 
end,  and  force  them  towards  each  other.  The  folding  of  the  cloths 
will  exactly  imitate  those  of  the  bent  strata.  (See  fig.  65.) 

Whether  the  analogous  flexures  in  stratified  rocks  have  really  been 
due  to  similar  sideway  movements  is  a  question  of  considerable  diffi- 
culty. It  will  appear  when  the  volcanic  and  granitic  rocks  are  de- 
scribed that  some  of  them  have,  when  melted,  been  injected  forcibly 
into  fissures,  while  others,  already  in  a  solid  state,  have  been  pro- 
truded upwards  through  the  incumbent  crust  of  the  earth,  by  which 
a  great  displacement  of  flexible  strata  must  have  been  caused. 

But  we  also  know  by  the  study  of  regions  liable  to  earthquakes, 
that  there  are  causes  at  work  in  the  interior .  of  the  earth  capable  of 
producing  a  sinking  in  of  the  ground,  sometimes  very  local,  but  some- 
times extending  over  a  wide  area.  The  frequent  repetition,  or  con- 
tinuance throughout  long  periods,  of  such  downward  movements 
seems  to  imply  the  formation  and  renewal  of  cavities  at  a  certain 
depth  below  the  surface,  whether  by  the  removal  of  matter  by  vol- 
canos  and  hot  springs,  or  by  the  contraction  of  argillaceous  rocks  by 
heat  and  pressure,  or  any  other  combination  of  circumstances.  What- 
ever conjectures  we  may  indulge  respecting  the  causes,  it  is  certain 
that  pliable  beds  may,  in  consequence  of  unequal  degrees  of  subsi- 
dence, become  folded  to  any  amount,  and  have  all  the  appearance  of 
having  been  compressed  suddenly  by  a  lateral  thrust. 

The  "  Creeps,"  as  they  are  called  in  coal-mines,  afford  an  excellent 
illustration  of  this  fact. — First,  it  may  be  stated  generally,  that  the 
excavation  of  coal  at  a  considerable  depth  causes  the  mass  of  over- 
lying strata  to  sink  down  bodily,  even  when  props  are  left  to  support 
the  roof  of  the  mine.  "  In  Yorkshire,"  says  Mr.  Buddie,  "  three  dis- 
tinct subsidences  were  perceptible  at  the  surface,  after  the  clearing 
out  of  three  seams  of  coal  below,  and  innumerable  vertical  cracks 
were  caused  in  the  incumbent  mass  of  sandstone  and  shale,  which 
thus  settled  down."  *  The  exact  amount  of  depression  in  these  cases 

*  Proceedings  of  Geol.  Soc.  vol.iii.  p.  148. 


CH.  V.]  CREEPS   IN  COAL-MINES.  51 

can  only  be  accurately  measured  where  water  accumulates  on  the 
surface,  or  a  railway  traverses  a  coal-field. 

"When  a  bed  of  coal  is  worked  out,  pillars  or  rectangular  masses 
of  coal  are  left  at  intervals  as  props  to  support  the  roof,  and  protect 
the  colliers.  Thus  in  fig.  66.,  representing  a  section  at  Wallsend, 


Newcastle,  the  galleries  which  have  been  excavated  are  represented 
by  the  white  spaces  a  b,  while  the  adjoining  dark  portions  are  parts 
of  the  original  coal-seam  left  as  props,  beds  of  sandy  clay  or  shale 
constituting  the  floor  of  the  mine.  When  the  props  have  been  re- 

E  2 


52  CURVED    STRATA.  [Cn.  V. 

duced  in  size,  they  are  pressed  down  by  the  weight  of  overlying  rocks 
(no  less  than  630  feet  thick)  upon  the  shale  below,  which  is  thereby 
squeezed  and  forced  up  into  the  open  spaces. 

Now  it  might  have  been  expected,  that  instead  of  the  floor  rising 
up,  the  ceiling  would  sink  down,  and  this  effect,  called  a  "  Thrust," 
does,  in  fact,  take  place  where  the  pavement  is  more  solid  than  the 
roof.  But  it  usually  happens,  in  coal-mines,  that  the  roof  is  com- 
posed of  hard  shale,  or  occasionally  of  sandstone,  more  unyielding 
than  the  foundation,  which  often  consists  of  clay.  Even  where  the 
argillaceous  substrata  are  hard  at  first,  they  soon  become  softened 
and  reduced  to  a  plastic  state  when  exposed  to  the  contact  of  air  and 
water  in  the  floor  of  a  mine. 

The  first  symptom  of  a  "  creep,"  says  Mr.  Buddie,  is  a  slight  cur- 
vature at  the  bottom  of  each  gallery,  as  at  a,  fig.  66.:  then  the 
pavement  continuing  to  rise,  begins  to  open  with  a  longitudinal 
crack,  as  at  b :  then  the  points  of  the  fractured  ridge  reach  the  roof, 
as  at  c  ;  and,  lastly,  the  upraised  beds  close  up  the  whole  gallery,  and 
the  broken  portions  of  the  ridge  are  re-united  and  flattened  at  the 
top,  exhibiting  the  flexure  seen  at  d.  Meanwhile  the  coal  in  the 
props  has  become  crushed  and  cracked  by  pressure.  It  is  also  found 
that  below  the  creeps  a,  b,  c,  d,  an  inferior  stratum,  called  the 
"  metal  coal,"  which  is  3  feet  thick,  has  been  fractured  at  the  points 
e,  f,  g,  h,  and  has  risen,  so  as  to  prove  that  the  upward  movement, 
caused  by  the  working  out  of  the  "  main  coal,"  has  been  propagated 
through  a  thickness  of  54  feet  of  argillaceous  beds,  which  intervene 
between  the  two  coal  seams.  This  same  displacement  has  also  been 
traced  downwards  more  than  150  feet  below  the  metal  coal,  but  it 
grows  continually  less  and  less  until  it  becomes  imperceptible. 

No  part  of  the  process  above  described  is  more  deserving  of  our 
notice  than  the  slowness  with  which  the  change  in  the  arrangement 
of  the  beds  is  brought  about.  Days,  months,  or  even  years,  will 
sometimes  elapse  between  the  first  bending  of  the  pavement  and  the 
time  of  its  reaching  the  roof.  Where  the  movement  has  been  most 
rapid,  the  curvature  of  the  beds  is  most  regular,  and  the  reunion  of 
the  fractured  ends  most  complete ;  whereas  the  signs  of  displacement 
or  violence  are  greatest  in  those  creeps  which  have  required  months 
or  years  for  their  entire  accomplishment.  Hence  we  may  conclude 
that  similar  changes  may  have  been  wrought  on  a  larger  scale  in  the 
earth's  crust  by  partial  and  gradual  subsidences,  especially  where 
the  ground  has  been  undermined  throughout  long  periods  of  time  ; 
and  we  must  be  on  our  guard  against  inferring  sudden  violence, 
simply  because  the  distortion  of  the  beds  is  excessive. 

Between  the  layers  of  shale,  accompanying  coal,  we  sometimes  see 
the  leaves  of  fossil  ferns  spread  out  as  regularly  as  dried  plants 
between  sheets  of  paper  in  the  herbarium  of  a  botanist.  These  fern- 
leaves,  or  fronds,  must  have  rested  horizontally  on  soft  mud,  when 
first  deposited.  If,  therefore,  they  and  the  layers  of  shale  are  now 
inclined,  or  standing  on  end,  it  is  obviously  the  effect  of  subsequent 
derangement.  The  proof  becomes,  if  possible,  still  more  striking 


CH.  V.] 


DIP  AND   STRIKE. 


53 


when  these  strata,  including  vegetable  remains,  are  curved  again  ana 
again,  and  even  folded  into  the  form  of  the  letter  Z,  so  that  the  same 
continuous  layer  of  coal  is  cut  through  several  times  in  the  same 
perpendicular  shaft.  Thus,  in  the  coal-field  near  Mons,  in  Belgium, 

Fig.  67. 


Fig.  68. 


Zigzag  "flexures  of  coal  near  Mons. 

these  zigzag  bendings  are  repeated  four  or  five  times,  in  the  manner 
represented  in  fig.  67.,  the  black  lines  representing  seams  of  coal.* 

Dip  and  Strike.  —  In  the  above  remarks,  several  technical  terms 
have  been  used,  such  as  dip,  the  unconformable  position  of  strata, 
and  the  anticlinal  and  synclinal  lines,  which,  as  well  as  the  strike  of 
the  beds,  I  shall  now  explain.  If  a  stratum  or  bed  of  rock,  instead 
of  being  quite  level,  be  inclined  to  one  side,  it  is  said  to  dip;  the 
point  of  the  compass  to  which  it  is  inclined  is  called  the  point  of  dip, 
and  the  degree  of  deviation  from  a  level  or  horizontal  line  is  called 

the  amount  of  dip,  or  the  angle 
of  dip.  -  Thus,  in  the  annexed 
diagram  (fig.  68.),  a  series  of 
strata  are  inclined,  and  they  dip 
to  the  north  at  an  angle  of  forty- 
five  degrees.  The  strike,  or  line 
of  bearing,  is  the  prolongation  or  extension  of  the  strata  in  a  direction 
at  right  angles  to  the  dip ;  and  hence  it  is  sometimes  called  the  di- 
rection of  the  strata.  Thus,  in  the  above  instance  of  strata  dipping 
to  the  north,  their  strike  must  necessarily  be  east  and  west.  We 
have  borrowed  the  word  from  the  German  geologists,  streichen  sig- 
nifying to  extend,  to  have  a  certain  direction.  Dip  and  strike  may 
be  aptly  illustrated  by  a  row  of  houses  running  east  and  west,  the 
long  ridge  of  the  roof  representing  the  strike  of  the  stratum  of  slates, 
which  dip  on  one  side  to  the  north,  and  on  the  other  to  the  south. 

A  stratum  which  is  horizontal,  or  quite  level  in  all  directions,  has 
neither  dip  nor  strike. 

It  is  always  important  for  the  geologist,  who  is  endeavouring  to 
comprehend  the  structure  of  a  country,  to  learn  how  the  beds  dip  in 
every  part  of  the  district ;  but  it  requires  some  practice  to  avoid 
being  occasionally  deceived,  both  as  to  the  point  of  dip  and  the 
amount  of  it. 

*  See  plan  by  M.  Chevalier,  Burat's  D'Aubuisson,  torn.  ii.  p.  334. 
E  3 


54 


DIP   AND   STRIKE. 


[On.  V. 


If  the  upper  surface  of  a  hard  stony  stratum  be  uncovered,  whether 
artificially  in  a  quarry,  or  by  the  waves  at  the  foot  of  a  cliff,  it  is 
easy  to  determine  towards  what  point  of  the  compass  the  slope  is 
steepest,  or  in  what  direction  water  would  flow,  if  poured  upon  it. 
This  is  the  true  dip.  But  the  edges  of  highly  inclined  strata  may 
give  rise  to  perfectly  horizontal  lines  in  the  face  of  a  vertical  cliff,  if 
the  observer  see  the  strata  in  the  line  of  their  strike,  the  dip  being 
inwards  from  the  face  of  the  cliff.  If,  however,  we  come  to  a  break 
in  the  cliff,  which  exhibits  a  section  exactly  at  right  angles  to  the 
line  of  the  strike,  we  are  then  able  to  ascertain  the  true  dip.  In  the 
annexed  drawing  (fig.  69.),  we  may  suppose  a  headland,  one  side  of 

Fig.  69. 


Apparent  horizontality  of  inclined  strata. 

which  faces  to  the  north,  where  the  beds  would  appear  perfectly 
horizontal  to  a  person  in  the  boat;  while  in  the  other  side  facing  the 
west,  the  true  dip  would  be  seen  by  the  person  on  shore  to  be  at  an 
angle  of  40°.  If,  therefore,  our  observations  are  confined  to  a  vertical 
precipice  facing  in  one  direction,  we  must  endeavour  to  find  a  ledge 
or  portion  of  the  plane  of  one  of  the  beds  projecting  beyond  the 
others,  in  order  to  ascertain  the  true  dip. 

It  is  rarely  important  to  determine  the  angle  of  inclination  with 
such  minuteness  as  to  require  the  aid  of  the  instrument  called  a 
clinometer.     We  may  measure  the  angle  within  a  few  degrees  by 
Fig.  70.  standing  exactly  opposite  to  a  cliff  where 

the  true  dip  is  exhibited,  holding  the 
hands  immediately  before  the  eyes,  and 
placing  the  fingers  of  one  in  a  perpen- 
dicular, and  of  the  other  in  a  horizontal 
position,  as  in  fig.  70.  It  is  thus  easy 
to  discover  whether  the  lines  of  the  in- 
clined beds  bisect  the  angle  of  90°,  formed 
by  the  meeting  of  the  hands,  so  as  to  give 
an  angle  of  45°,  or  whether  it  would  di- 
vide the  space  into  two  equal  or  unequal 
portions.  The  upper  dotted  line  may  express  a  stratum  dipping  to 
the  north ;  but  should  the  beds  dip  precisely  to  the  opposite  point  of 


CH.  V.J 


DIP   AND   STRIKE. 


55 


the  compass  as  in  the  lower  dotted  line,  it  will  be  seen  that  the  amount 
of  inclination  may  still  be  measured  by  the  hands  with  equal  facility. 
It  has  been  already  seen,  in  describing  the  curved  strata  on  the 
east  coast  of  Scotland,  in  Forfarshire  and  Berwickshire,  that  a  series 
of  concave  and  convex  bendings  are  occasionally  repeated  several 
times.  These  usually  form  part  of  a  series  of  parallel  waves  of 
strata,  which  are  prolonged  in  the  same  direction  throughout  a  con- 
siderable extent  of  country.  Thus,  for  example,  in  the  Swiss  Jura, 
that  lofty  chain  of  mountains  has  been  proved  to  consist  of  many 
parallel  ridges,  with  intervening  longitudinal  valleys,  as  in  fig.  71., 
the  ridges  being  formed  by  curved  fossiliferous  strata,  of  which 
the  nature  and  dip  are  occasionally  displayed  in  deep  transverse 
gorges,  called  "  cluses,"  caused  by  fractures  at  right  angles  to  the 
direction  of  the  chain.*  Now  let  us  suppose  these  ridges  and  parallel 
valleys  to  run  north  and  south,  we  should  then  say  that  the  strike  of 
the  beds  is  north  and  south,  and  the  dip  east  and  west.  Lines 
drawn  along  the  summits  of  the  ridges,  A,  B,  would  be  anticlinal 
lines,  and  one  following  the  bottom  of  the  adjoining  valleys  a  syn- 
clinal line.  It  will  be  observed  that  some  of  these  ridges,  A,  B,  are 
unbroken  on  the  summit,  whereas  one  of  them,  C,  has  been  fractured 
along  the  line  of  strike,  and  a  portion  of  it  carried  away  by  denud- 
ation, so  that  the  ridges  of  the  beds  in  the  formations  a,  b,  c,  come 

Fig.  71. 


Section  illustrating  the  structure  of  the  Swiss  Jura. 


Fig.  72. 


Fig.  73. 


Ground  plan  of  the  denuded  ridge  C,  fig.  71. 


out  to  the  day,  or,  as  the  miners 

say,  crop  out,  on  the  sides  of  a 

|  valley.     The  ground  plan  of  such 

1  a  denuded  ridge  as  C,  as  given 

|  in  a  geological  map,  may  be  ex- 

|  pressed  by  the  diagram  fig.  72., 

|  and  the  cross  section  of  the  same 

by  fig.  73.     The  line  D  E,  fig.  72., 

is  the  anticlinal  line,  on  each  side 


*  See  M.  Thunnann's  work, 
sur  les  Soulevemens  Jurassiques  du  Por- 


rentruy,  Paris,  1832,"  with  whom  I  ex- 
amined part  of  these  mountains  in  1835. 


E  4 


56  OUTCROP  OF  STRATA.  [Cn.  V. 

of  which  the  dip  is  in  opposite  directions,  as  expressed  by  the 
arrows.  The  emergence  of  strata  at  the  surface  is  called  by  miners 
their  out-crop  or  basset. 

If,  instead  of  being  folded  into  parallel  ridges,  the  beds  form  a 
boss  or  dome-shaped  protuberance,  and  if  we  suppose  the  summit 
of  the  dome  carried  off,  the  ground  plan  would  exhibit  the  edges  of 
the  strata  forming  a  succession  of  circles,  or  ellipses,  round  a  com- 
mon centre.  These  circles  are  the  lines  of  strike,  and  the  dip  being 
always  at  right  angles  is  inclined  in  the  course  of  the  circuit  to  every 
point  of  the  compass,  constituting  what  is  termed  a  qua-quaversal 
dip  —  that  is,  turning  each  way. 

There  are  endless  variations  in  the  figures  described  by  the  basset- 
edges  of  the  strata,  according  to  the  different  inclination  of  the  beds, 
and  the  mode  in  which  they  happen  to  have  been  denuded.  One  of 
the  simplest  rules  with  which  every  geologist  should  be  acquainted, 
relates  to  the  V-like  form  of  the  beds  as  they  crop  out  in  an  ordinary 
valley.  First,  if  the  strata  be  horizontal,  the  V-like  form  will  be 
also  on  a  level,  and  the  newest  strata  will  appear  at  the  greatest 
heights. 

Secondly,  if  the  beds  be  inclined  and  intersected  by  a  valley 
sloping  in  the  same  direction,  and  the  dip  of  the  beds  be  less  steep 
than  the  slope  of  the  valley,  then  the  V's,  as  they  are  often  termed 
by  miners,  will  point  upwards  (see  fig.  74.),  those  formed  by  the 

newer  beds  appearing  in 
a  superior  position,  and 
extending  highest  up  the 
valley,  as  A  is  seen  above 
B. 

Thirdly,  if  the  dip  of 
the  beds  be  steeper  than 
the  slope  of  the  valley, 
then  the  V's  will  point 
downwards  (see  fig.  75.), 
and  those  formed  of  the 
older  beds  will  now  appear 
uppermost,  as  B  appears 
above  A. 

Fourthly,  in  every  case 
where  the  strata  dip  in  a 
contrary  direction  to  the 
slope  of  the  valley,  what- 
ever be  the  angle  of  in- 
clination, the  newer  beds 
will  appear  the  highest, 
as  in  the  first  and  second 
cases.  This  is  shown  by 
the  drawing  (fig.  76.), 

^^^  which  exhibits  strata  ris- 

siope  01  valley -20°,  dip  of  strata  5<p.  ing  at  an   angle  of  20°, 


Fig.  74. 


Slope  of  valley  40°,  dip  of  strata  20°. 
Fig.  75 


CH.  V.]  ANTICLINAL   AND   SYNCLINAL    LINES.  57 

Fig-76-  and  crossed   by  a   valley, 

which  declines  in  an  oppo- 
site direction  at  20°.* 
«£  These  rules  may  often 

be  of  great  practical  uti- 
lity ;  for  the  different  de- 
..20"  grees  of  dip  occurring  in 
the  two  cases  represented 
in  figures  74  and  75.  may 
occasionally  be  encoun- 
tered in  following  the  same 
line  of  flexure  at  points 
a  few  miles  distant  from 

Slope  of  valley  20°,  dip  of  strata  20°,  in  opposite  directions.  t,      *-L  A 

each  other.  A  miner  un- 
acquainted with  the  rule,  who  had  first  explored  the  valley  (fig. 
74.),  may  have  sunk  a  vertical  shaft  below  the  coal  seam  A,  until 
he  reached  the  inferior  bed  B.  He  might  then  pass  to  the  valley 
fig.  75.,  and  discovering  there  also  the  outcrop  of  two  coal  seams, 
might  begin  his  workings  in  the  uppermost  in  the  expectation  of 
coming  down  to  the  other  bed  A,  which  would  be  observed  cropping 
out  lower  down  the  valley.  But  a  glance  at  the  section  will  demon- 
strate the  futility  of  such  hopes. 

In  the  majority  of  cases,  an  anticlinal  axis  forms  a  ridge,  and  a 
synclinal  axis  a  valley,  as  in  A,  B,  fig.  62.  p.  48. ;  but  there  are 
Fig.  77,  exceptions  to  this  rule,  the  beds  sometimes 

sloping  inwards  from  either  side  of  a  moun- 
tain, as  in  fig.  77. 

On  following  one  t>f  the  anticlinal  ridges 
of  the  Jura,  before  mentioned,  A,  B,  C,  fig. 
71.,  we  often  discover  longitudinal  cracks 
and  sometimes  large  fissures  along  the  line 
where  the  flexure  was  greatest.  Some  of  these,  as  above  stated, 
have  been  enlarged  by  denudation  into  valleys  of  considerable  width, 
as  at  C,  fig.  71.,  which  follow  the  line  of  strike,  and  which  we  may 
suppose  to  have  been  hollowed  out  at  the  time  when  these  rocks  were 
still  beneath  the  level  of  the  sea,  or  perhaps  at  the  period  of  their 
gradual  emergence  from  beneath  the  waters.  The  existence  of  such 
cracks  at  the  point  of  the  sharpest  bending  of  solid  strata  of  limestone 
is  precisely  what  we  should  have  expected;  but  the  occasional 
want  of  all  similar  signs  of  fracture,  even  where  the  strain  has  been 
greatest,  as  at  a,  fig.  71.,  is  not  always  easy  to  explain.  We  must 
imagine  that  many  strata  of  limestone,  chert,  and  other  rocks  which 
are  now  brittle,  were  pliant  when  bent  into  their  present  position. 

*  I  am  indebted  to  the  kindness  of  originals,  turning  them  about  in  different 

T.  Sopwith,  Esq.,  for  three  models  which  ways,  he  would  at  once  comprehend  their 

I  have  copied  in  the  above  diagrams  ;  meaning  as  well  as  the  import  of  others 

but  the  beginner  may  find  it  by  no  means  far  more  complicated,  which  the  same 

easy  to  understand  such  copies,  although,  engineer  has  constructed   to    illustrate 

if  he  were  to  examine  and  handle  the  faults. 


58 


REVERSED   DIP   OF    STRATA. 


[On.  V. 


They  may  have  owed  their  flexibility  in  part  to  the  fluid  matter 
which  they  contained  in  their  minute  pores,  as  before  described 
(p.  35.),  and  in  part  to  the  permeation  of  sea-water  while  they  were 
yet  submerged. 

At  the  western  extremity  of  the  Pyrenees,  great  curvatures  of  the 
strata  are  seen  in  the  sea  cliffs,  where  the  rocks  consist  of  marl,  grit, 
and  chert.  At  certain  points,  as  at  a,  fig.  78.,  some  of  the  bendings 

Fig.  78. 


Fig.  79. 


Strata  of  chert,  grit,  and  marl,  near  St.  Jean  de  Luz. 

of  the  flinty  chert  are  so  sharp,  that  specimens  might  be  broken  off, 
well  fitted  to  serve  as  ridge-tiles  on  the  roof  of  a  house.  Although 
this  chert  could  not  have  been  brittle  as  now,  when  first  folded  into 
this  shape,  it  presents,  nevertheless,  here  and  there  at  the  points  of 
greatest  flexure  small  cracks,  which  show  that  it  was  solid,  and  not 
wholly  incapable  of  breaking  at  the  period  of  its  displacement.  The 
numerous  rents  alluded  to  are  not  empty,  but  filled  with  calcedony 
and  quartz. 

Between  San  Caterina  and  Castrogiovanni,  in  Sicily,  bent  and 
undulating  gypseous  marls  occur,  with  here  and  there  thin  beds  of 
solid  gypsum  interstratified.  Sometimes 
these  solid  layers  have  been  broken  into 
detached  fragments,  still  preserving  their 
sharp  edges  (g  g,  fig.  79.),  while  the  con- 
tinuity of  the  more  pliable  and  ductile 
marls,  m  m,  has  not  been  interrupted. 

I   shall  conclude  my  remarks  on  bent 
strata  by  stating,   that,  in  mountainous 

g.  gypsum,     m.  mari.  regions  like  the  Alps,  it  is  often  difficult 

for  an  experienced  geologist  to  determine  correctly  the  relative  age 
of  beds  by  superposition,  so  often  have  the  strata  been  folded  back 
upon  themselves,  the  upper  parts  of  the  curve  having  been  removed 
by  denudation.  Thus,  if  we  met  with  the  strata  seen  in  the  section 
fig.  80.,  we  should  naturally  suppose  that  there  were  twelve  distinct 

beds,  or  sets  of  beds,  No.  1.  being  the 
newest,  and  No.  12.  the  oldest  of  the 
series.  But  this  section  may,  perhaps, 
exhibit  merely  six  beds,  which  have 
been  folded  in  the  manner  seen  in 
fig.  81.,  so  that  each  of  them  is  twice  repeated,  the  position  of  one 
half  being  reversed,  and  part  of  No.  1.,  originally  the  uppermost, 
having  now  become  the  lowest  of  the  series.  These  phenomena  are 
often  observable  on  a  magnificent  scale  in  certain  regions  in  Switzer- 
land in  precipices  from  2000  to  3000  feet  in  perpendicular  height. 


Fig.  80. 


3\2\J 


CH.  V.] 


CURVED   STRATA   IN   THE   ALPS. 

Fig.  81. 


59 


m\\\\\\\\\A 


In  the  Iselten  Alp,  in  the  valley  of  the  Lutschine,  between  Unterseen 
and  Grindelwald,  curves  of  calcareous  shale  are  seen  from  1000  to 
1500  feet  in  height,  in  which  the  beds  sometimes  plunge  down  ver- 
tically for  a  depth  of  1000  feet  and  more,  before  they  bend  round 

Fig.  82. 


Curved  strata  of  the  Iselten  Alp. 


again.     There  are  many  flexures  not  inferior  in  dimensions  in  the 
Pyrenees,  as  those  near  Gavarnie,  at  the  base  of  Mont  Perdu. 

Unconformable  stratification.  —  Strata  are  said  to  be  unconform- 
able,  when  one  series  is  so  placed  over  another,  that  the  planes  of  the 
superior  repose  on  the  edges  of  the  inferior  (see  fig.  83.).  In  this 


Fig.  83. 


Unconformabie  junction  of  old  red  sandstone  and  Silurian  schist  at  the  Siccar  Point,  near  St.  Abb's 
Head,  Berwickshire.    See  also  Frontispiece. 

case  it  is  evident  that  a  period  had  elapsed  between  the  production 
of  the  two  sets  of  strata,  and  that,  during  this  interval,  the  older 


60  UNCONFOKMABLE   STRATIFICATION.  [Cn.  V. 

series  had  been  tilted  and  disturbed.  Afterwards  the  upper  series 
was  thrown  down  in  horizontal  strata  upon  it.  If  these  superior 
beds,  as  d,  d,  fig.  83.,  are  also  inclined,  it  is  plain  that  the  lower 
strata,  #,  a,  have  been  twice  displaced ;  first,  before  the  deposition  of 
the  newer  beds,  d,  d,  and  a  second  time  when  these  same  strata  were 
thrown  out  of  the  horizontal  position. 

Playfair  has  remarked*  that  this  kind  of  junction  which  we  now 
call  unconformable  had  been  described  before  the  time  of  Hutton, 
but  that  he  was  the  first  geologist  who  appreciated  its  importance,  as 
illustrating  the  high  antiquity  and  great  revolutions  of  the  globe. 
He  had  observed  that  where  such  contacts  occur,  the  lowest  beds  of 
the  newer  series  very  generally  consist  of  a  breccia  or  conglomerate 
consisting  of  angular  and  rounded  fragments,  derived  from  the  break- 
ing up  of  the  more  ancient  rocks.  On  one  occasion  the  Scotch 
geologist  took  his  two  distinguished  pupils,  Playfair  and  Sir  James 
Hall,  to  the  cliffs  on  the  east  coast  of  Scotland,  near  the  village  of 
Eyemouth,  not  far  from  St.  Abb's  Head,  where  the  schists  of  the 
Lammermuir  range  are  undermined  and  dissected  by  the  sea.  Here 
the  curved  and  vertical  strata,  now  known  to  be  of  Silurian  age,  and 
which  often  exhibit  a  ripple-marked  surface,  are  well  exposed  at 
the  headland  called  the  Siccar  Point,  penetrating  with  their  edges 
into  the  incumbent  beds  of  slightly  inclined  sandstone,  in  which  large 
pieces  of  the  schist,  some  round  and  others  angular,  are  united  by  an 
arenaceous  cement.  "What  clearer  evidence,"  exclaims  Playfair, 
"  could  we  have  had  of  the  different  formation  of  these  rocks,  and  of 
the  long  interval  which  separated  their  formation,  had  we  actually 
seen  them  emerging  from  the  bosom  of  the  deep  ?  We  felt  ourselves 
necessarily  carried  back  to  the  time  when  the  schistus  on  which  we 
stood  was  yet  at  the  bottom  of  the  sea,  and  when  the  sandstone  before 
us  was  only  beginning  to  be  deposited  in  the  shape  of  sand  or  mud, 
from  the  waters  of  a  superincumbent  ocean.  An  epoch  still  more 
remote  presented  itself,  when  even  the  most  ancient  of  these  rocks, 
instead  of  standing  upright  in  vertical  beds,  lay  in  horizontal  planes 
at  the  bottom  of  the  sea,  and  was  not  yet  disturbed  by  that  immea- 
surable force  which  has  burst  asunder  the  solid  pavement  of  the 
globe.  Revolutions  still  more  remote  appeared  in  the  distance  of 
this  extraordinary  perspective.  The  mind  seemed  to  grow  giddy  by 
looking  so  far  into  the  abyss  of  time  ;  and  while  we  listened  with 
earnestness  and  admiration  to  the  philosopher  who  was  now  unfold- 
ing to  us  the  order  and  series  of  these  wonderful  events,  we  became 
sensible  how  much  farther  reason  may  sometimes  go  than  imagina- 
tion can  venture  to  follow."  f 

In  the  frontispiece  of  this  volume  the  reader  will  see  a  view  of  this 
classical  spot,  reduced  from  a  large  picture,  faithfully  drawn  and 
coloured  from  nature  by  the  youngest  son  of  the  late  Sir  James  Hall. 
It  was  impossible,  however,  to  do  justice  to  the  original  sketch,  in  an 


Biographical  account  of  Dr.  Hutton. 

Playfair,  ibid.;  see  his  Works,  Edin.  1822,  vol.  ir.  p.  81. 


FISSURES   IN   STRATA. 


61 


CH.  V.] 

engraving,  as  the  contrast  of  the  red  sandstone  and  the  light  fawn- 
coloured  vertical  schists  could  not  be  expressed.  From  the  point  of 
view  here  selected,  the  underlying  beds  of  the  perpendicular  schist,  a, 
are  visible  at  b  through  a  small  opening  in  the  fractured  beds  of  the 
covering  of  red  sandstone,  d  d,  while  on  the  vertical  face  of  the  old 
schist  at  a'  a"  a  conspicuous  ripple-mark  is  displayed. 

It  often  happens  that  in  the  interval  between  the  deposition  of  two 
sets  of  unconformable  strata,  the  inferior  rock  has  not  only  been 
denuded,  but  drilled  by  perforating  shells.  Thus,  for  example,  at 
Autreppe  and  Gusigny,  near  Mons,  beds  of  an  ancient  (primary  or 

Fig.  84. 


Junction  of  unconformable  strata  near  Mons,  in  Belgium. 

paleozoic)  limestone,  highly  inclined,  and  often  bent,  are  covered  with 
horizontal  strata  of  greenish  and  whitish  marls  of  the  Cretaceous 
formation.  The  lowest  and  therefore  the  oldest  bed  of  the  horizontal 
series  is  usually  the  sand  and  conglomerate,  a,  in  which  are  rounded 
fragments  of  stone,  from  an  inch  to  two  feet  in  diameter.  These  frag- 
ments have  often  adhering  shells  attached  to  them,  and  have  been 
bored  by  perforating  mollusca.  The  solid  surface  of  the  inferior 
limestone  has  also  been  bored,  so  as  to  exhibit  cylindrical  and  pear- 
shaped  cavities,  as  at  <?,  the  work  of  saxicavous  mollusca;  and  many 
rents,  as  at  6,  which  descend  several  feet  or  yards  into  the  limestone, 
have  been  filled  with  sand  and  shells,  similar  to  those  in  the  stratum  a. 

Fractures  of  the  strata  and  faults. — Numerous  rents  may  often  be 
seen  in  rocks  which  appear  to  have  been  simply  broken,  the  sepa- 
rated parts  remaining  in  the  same  places ;  but  we  often  find  a  fissure, 
several  inches  or  yards  wide,  intervening  between  the  disunited  por- 
tions. These  fissures  are  usually  filled  with  fine  earth  and  sand,  or 
with  angular  fragments  of  stone,  evidently  derived  from  the  fracture 
of  the  contiguous  rocks. 

It  is  not  uncommon  to  find  the  mass  of  rock,  on  one  side  of  a 
fissure  thrown  up  above  or  down  below  the  mass  with  which  it  was 
once  in  contact  on  the  other  side.  "  This  mode  of  displacement  is 
called  a  shift,  slip,  or  fault.  "  The  miner,"  says  Playfair,  describing  a 
fault,  "is  often  perplexed,  in  his  subterraneous  journey,  by  a  derange- 
ment in  the  strata,  which  changes  at  once  all  those  lines  and  bearings 
which  had  hitherto  directed  his  course.  When  his  mine  reaches  a 
certain  plane,  which  is  sometimes  perpendicular,  as  in  A  B,  fig.  85. , 
sometimes  oblique  to  the  horizon  (as  in  C  D,  ibid.),  he  finds  the  beds 
of  rock  broken  asunder,  those  on  the  one  side  of  the  plane  having 
changed  their  place,  by  sliding  in  a  particular  direction  along  the 
face  of  the  others.  In  this  motion  they  have  sometimes  preserved 
their  parallelism,  as  in  fig.  85.,  so  that  the  strata  on  each  side  of  the 


62 


[CH.  V. 


B  D 

Faults.    A  B  perpendicular,  C  D  oblique  to  the  horizon. 

faults  A  B,  C  D,  continue  parallel  to  one  another ;  in  other  cases,  the 
strata  on  each  side  are  inclined,  as  in  a,  bt  c,  d  (fig.  86.),  though 

Fig.  86. 


E  F,  fault  or  fissure  filled  with  rubbish,  on  each  side  of  which  the  shifted 
strata  are  not  parallel. 

their  identity  is  still  to  be  recognized  by  their  possessing  the  same 
thickness  and  the  same  internal  characters."* 

In  Coalbrook  Dale,  says  Mr.  Prestwich  f ,  deposits  of  sandstone, 
shale,  and  coal,  several  thousand  feet  thick,  and  occupying  an  area 
of  many  miles,  have  been  shivered  into  fragments,  and  the  broken 
remnants  have  been  placed  in  very  discordant  positions,  often  at 
levels  differing  several  hundred  feet  from  each  other.  The  sides  of 
the  faults,  when  perpendicular,  are  commonly  separated  several  yards, 
but  are  sometimes  as  much  as  50  yards  asunder,  the  interval  being 
filled  with  broken  debris  of  the  strata.  In  following  the  course  of 
the  same  fault  it  is  sometimes  found  to  produce  in  different  places 
very  unequal  changes  of  level,  the  amount  of  shift  being  in  one  place 
300,  and  in  another  700  feet,  which  arises,  in  some  cases,  from  the 
union  of  two  or  more  faults.  In  other  words,  the  disjointed  strata 
have  in  certain  districts  been  subjected  to  renewed  movements,  which 
they  have  not  suffered  elsewhere. 

We  may  occasionally  see  exact  counterparts  of  these  slips,  on  a 
small  scale,  in  pits  of  loose  sand  and  gravel,  many  of  which  have 
doubtless  been  caused  by  the  drying  and  shrinking  of  argillaceous 
and  other  beds,  slight  subsidences  having  taken  place  from  failure 
of  support.  Sometimes,  however,  even  these  small  slips  may  have 
been  produced  during  earthquakes ;  for  land  has  been  moved,  and  its 
level,  relatively  to  the  sea,  considerably  altered,  within  the  period 
when  much  of  the  alluvial  sand  and  gravel  now  covering  the  surface 
of  continents  was  deposited. 


*  Playfair,  Illust.  of  Hutt.  Theory, 


t  Geol.  Trans,  second  series,  voL  v. 
p.  452. 


CH.  V.] 


FAULTS. 


63 


I  have  already  stated  that  a  geologist  must  be  on  his  guard,  in  a 
region  of  disturbed  strata,  against  inferring  repeated  alternations  of 
rocks,  when,  in  fact,  the  same  strata,  once  continuous,  have  been 
bent  round  so  as  to  recur  in  the  same  section,  and  with  the  same  dip. 
A  similar  mistake  has  often  been  occasioned  by  a  series  of  faults. 

If,  for  example,  the  dark  line  A  H  (fig.  87.)  represent  the  surface 
of  a  country  on  which  the  strata  a  b  c  frequently  crop  out,  an  observer, 

Fig.  87. 


Apparent  alternations  of  strata  caused  by  vertical  faults. 

who  is  proceeding  from  H  to  A,  might  at  first  imagine  that  at  every 
step  he  was  approaching  new  strata,  whereas  the  repetition  of  the 
same  beds  has  been  caused  by  vertical  faults,  or  downthrows.  Thus, 
suppose  the  original  mass,  A,  B,  C,  D,  to  have  been  a  set  of  uniformly 
inclined  strata,  and  that  the  different  masses  under  E  F,  F  G,  and 
G  D,  sank  down  successively,  so  as  to  leave  vacant  the  spaces  marked 
in  the  diagram  by  dotted  lines,  and  to  occupy  those  marked  by  the 
continuous  lines,  then  let  denudation  take  place  along  the  line  A  H, 
so  that  the  protruding  masses  indicated  by  the  fainter  lines  are  swept 
away,  —  a  miner,  who  has  not  discovered  the  faults,  finding  the  mass 
a,  which  we  will  suppose  to  be  a  bed  of  coal  four  times  repeated, 
might  hope  to  find  four  beds,  workable  to  an  indefinite  depth,  but 
first  on  arriving  at  the  fault  G  he  is  stopped  suddenly  in  his  workings, 
upon  reaching  the  strata  of  sandstone  c,  or  on  arriving  at  the  line  of 
fault  F  he  comes  partly  upon  the  shale  b,  and  partly  on  the  sandstone 
c,  and  on  reaching  E  he  is  again  stopped  by  a  wall  composed  of  the 
rock  d. 

The  very  different  levels  at  which  the  separated  parts  of  the  same 
strata  are  found  on  the  different  sides  of  the  fissure,  in  some  faults, 
is  truly  astonishing.  One  of  the  most  celebrated  in  England  is  that 
called  the  "  ninety-fathom  dike,"  in  the  coal-field  of  Newcastle.  This 
name  has  been  given  to  it,  because  the  same  beds  are  ninety  fathoms 
lower  on  the  northern  than  they  are  on  the  southern  side.  The 
fissure  has  been  filled  by  a  body  of  sand,  which  is  now  in  the  state 
of  sandstone,  and  is  called  the  dike,  which  is  sometimes  very  narrow, 
but  in  other  places  more  than  twenty  yards  wide.  *  The  walls  of  the 

*  Conybeare  and  Phillips,  Outlines,  &c.  p.  376. 


64  ORIGIN   OF   GREAT  FAULTS.  [Cn.  V. 

fissure  are  scored  by  grooves,  such  as  would  have  been  produced  if 
the  broken  ends  of  the  rock  had  been  rubbed  along  the  plane  of  the 
fault.*  In  the  Tynedale  and  Craven  faults,  in  the  north  of  England, 
the  vertical  displacement  is  still  greater,  and  the  fracture  has  ex- 
tended in  a  horizontal  direction  for  a  distance  of  thirty  miles  or  more. 
Some  geologists  consider  it  necessary  to  imagine  that  the  upward  or 
downward  movement  in  these  cases  was  accomplished  at  a  single 
stroke,  and  not  by  a  series  of  sudden  but  interrupted  movements. 
This  idea  appears  to  have  been  derived  from  a  notion  that  the  grooved 
walls  have  merely  been  rubbed  in  one  direction.  But  this  is  so  far 
from  being  a  constant  phenomenon  in  faults,  that  it  has  often  been 
objected  to  the  received  theory  respecting  those  polished  surfaces 
called  "  slickensides "  that  the  strias  are  not  always  parallel,  but 
often  curved  and  irregular.  It  has,  moreover,  been  remarked,  that 
not  only  the  walls  of  the  fissure  or  fault,  but  its  earthy  contents, 
sometimes  present  the  same  polished  and  striated  faces.  Now 
these  facts  seem  to  indicate  partial  changes  in  the  direction  of  the 
movement,  and  some  slidings  subsequent  to  the  first  filling  up  of 
the  fissure.  Suppose  the  mass  of  rock  A,  B,  C,  to  overlie  an  ex- 
tensive chasm  d  e,  formed  at  the  depth  of  several  miles,  whether  by 


the  gradual  contraction  in  bulk  of  a  melted  mass  passing  into  a  solid 
or  crystalline  state,  or  the  shrinking  of  argillaceous  strata,  baked  by  a 
moderate  heat,  or  by  the  subtraction  of  matter  by  volcanic  action,  or 
any  other  cause.  Now,  if  this  region  be  convulsed  by  earthquakes, 
the  fissures /#,  and  others  at  right  angles  to  them,  may  sever  the 
mass  B  from  A  and  from  C,  so  that  it  may  move  freely,  and  begin 
to  sink  into  the  chasm.  A  fracture  may  be  conceived  so  clean  and 
perfect  as  to  allow  it  to  subside  at  once  to  the  bottom  of  the  subter- 
ranean cavity ;  but  it  is  far  more  probable  that  the  sinking  will  be 
effected  at  successive  periods  during  different  earthquakes,  the  mass 
always  continuing  to  slide  in  the  same  direction  along  the  planes  of 
the  fissures/*^,  and  the  edges  of  the  falling  mass  being  continually 
more  broken  and  triturated  at  each  convulsion.  If,  as  is  not  im- 
probable, the  circumstances  which  have  caused  the  failure  of  support 
continue  in  operation,  it  may  happen  that  when  the  mass  B  has  filled 
the  cavity  first  formed,  its  foundations  will  again  give  way  under  it, 
so  that  it  will  fall  again  in  the  same  direction.  But,  if  the  direction 
should  change,  the  fact  could  not  be  discovered  by  observing  the 
slickensides,  because  the  last  scoring  would  efface  the  lines  of  pre- 
vious friction.  In  the  present  state  of  our  ignorance  of  the  causes 
of  subsidence,  an  hypothesis  which  can  explain  the  great  amount  of 
displacement  in  some  faults,  on  sound  mechanical  principles,  by  a 
*  Phillips,  Geology,  Lardner's  Cyclop,  p.  4 1. 


CH.  V.]  ORIGIN  OF   GREAT  FAULTS.  65 

succession  of  movements,  is  far  preferable  to  any  theory  which  as- 
sumes each  fault  to  have  been  accomplished  by  a  single  upcast  or 
downthrow  of  several  thousand  feet.  For  we  know  that  there  are 
operations  now  in  progress,  at  great  depths  in  the  interior  of  the 
earth,  by  which  both  large  and  small  tracts  of  ground  are  made  to 
rise  above  and  sink  below  their  former  level,  some  slowly  and  in- 
sensibly, others  suddenly  and  by  starts,  a  few  feet  or  yards  at  a  time ; 
whereas  there  are  no  grounds  for  believing  that,  during  the  last  3000 
years  at  least,  any  regions  have  been  either  upheaved  or  depressed, 
at  a  single  stroke,  to  the  amount  of  several  hundred,  much  less  several 
thousand  feet.  When  some  of  the  ancient  marine  formations  are 
described  in  the  sequel,  it  will  appear  that  their  structure  and  organic 
contents  point  to  the  conclusion,  that  the  floor  of  the  ocean  was  slowly 
sinking  at  the  time  of  their  origin.  The  downward  movement  was 
very  gradual,  and  in  Wales  and  the  contiguous  parts  of  England  a 
maximum  thickness  of  32,000  feet  (more  than  six  miles)  of  Carbon- 
iferous, Devonian,  and  Silurian  rock  was  formed,  whilst  the  bed  of  the 
sea  was  all  the  time  continuously  and  tranquilly  subsiding.  *  What- 
ever may  have  been  the  changes  which  the  solid  foundation  underwent, 
whether  accompanied  by  the  melting,  consolidation,  crystallization, 
or  desiccation  of  subjacent  mineral  matter,  it  is  clear  from  the  fact 
of  the  sea  having  remained  shallow  all  the  while  that  the  bottom 
never  sank  down  suddenly  to  the  depth  of  many  hundred  feet  at 
once. 

It  is  by  assuming  such  reiterated  variations  of  level,  each  separately 
of  small  vertical  amount,  but  multiplied  by  time  till  they  acquire  im- 
portance in  the  aggregate,  that  we  are  able  to  explain  the  phenomena 
of  denudation,  which  will  be  treated  of  in  the  next  chapter.  By  such 
movements,  every  portion  of  the  surface  of  the  land  becomes  in  its 
turn  a  line  of  coast,  and  is  exposed  to  the  action  of  the  waves  and 
tides.  A  country  which  is  undergoing  such  movement  is  never 
allowed  to  settle  into  a  state  of  equilibrium,  therefore  the  force  of 
rivers  and  torrents  to  remove  or  excavate  soil  and  rocky  masses  is 
sustained  in  undiminished  energy. 

*  See  the  results  of  the  "  Geological  Survey  of  Great  Britain  ;  "  Memoirs,  vols.  L 
and  ii.,  by  Sir  H.  De  la  Beche,  Mr.  A.  C.  Ramsay,  and  Mr.  John  Phillips. 


66  DENUDATION   OF   KOCKS.  [Cn.  VI. 


CHAPTER  VI. 

DENUDATION. 

Denudation  defined — Its  amount  equal  to  the  entire  mass  of  stratified  deposits  in 
the  earth's  crust — Horizontal  sandstone  denuded  in  Koss-shire — Levelled  surface 
of  countries  in  which  great  faults  occur — Coalbrook  Dale— Denuding  power  of 
the  ocean  during  the  emergence  of  land — Origin  of  Valleys  —  Obliteration  of  sea- 
cliffs —  Inland  sea-cliffs  and  terraces  in  the  Morea  and  Sicily — Limestone  pillars 
at  St.  Mihiel,  in  France  —  in  Canada — in  the  Bermudas. 

DENUDATION,  which  has  been  occasionally  spoken  of  in  the  preceding 
chapters,  is  the  removal  of  solid  matter  by  water  in  motion,  whether  of 
rivers  or  of  the  waves  and  currents  of  the  sea,  and  the  consequent  lay- 
ing bare  of  some  inferior  rock.  Geologists  have  perhaps  been  seldom 
in  the  habit  of  reflecting  that  this  operation'  has  exerted  an  influence 
on  the  structure  of  the  earth's  crust  as  universal  and  important  as 
sedimentary  deposition  itself ;  for  denudation  is  the  inseparable  ac- 
companiment of  the  production  of  all  new  strata  of  mechanical  origin. 
The  formation  of  every  new  deposit  by  the  transport  of  sediment  and 
pebbles  necessarily  implies  that  there  has  been,  somewhere  else,  a 
grinding  down  of  rock  into  rounded  fragments,  sand,  or  mud,  equal  in 
quantity  to  the  new  strata.  All  deposition,  therefore,  except  in  the  case 
of  a  shower  of  volcanic  ashes,  is  the  sign  of  superficial  waste  going  on 
contemporaneously,  and  to  an  equal  amount  elsewhere.  The  gain  at 
one  point  is  no  more  than  sufficient  to  balance  the  loss  at  some  other. 
Here  a  lake  has  grown  shallower,  there  a  ravine  has  been  deepened. 
The  bed  of  the  sea  has  in  one  region  been  raised  by  the  accumulation 
of  new  matter,  in  another  its  depth  has  been  augmented  by  the 
abstraction  of  an  equal  quantity. 

When  we  see  a  stone  building,  we  know  that  somewhere,  far  or 
near,  a  quarry  has  been  opened.  The  courses  of  stone  in  the  building 
may  be  compared  to  successive  strata,  the  quarry  to  a  ravine  or  valley 
which  has  suffered  denudation.  As  the  strata,  like  the  courses  of 
hewn  stone,  have  been  laid  one  upon  another  gradually,  so  the  ex- 
cavation both  of  the  valley  and  quarry  have  been  gradual.  To  pursue 
the  comparison  still  farther,  the  superficial  heaps  of  mud,  sand,  and 
gravel,  usually  called  alluvium,  may  be  likened  to  the  rubbish  of  a 
quarry  which  has  been  rejected  as  useless  by  the  workmen,  or  has 
fallen  upon  the  road  between  the  quarry  and  the  building,  so  as  to 
lie  scattered  at  random  over  the  ground. 

If,  then,  the  entire  mass  of  stratified  deposits  in  the  earth's  crust 
is  at  once  the  monument  and  measure  of  the  denudation  which  has 
taken  place,  on  how  stupendous  a  scale  ought  we  to  find  the  signs  of 
this  removal  of  transported  materials  in  past  ages !  Accordingly, 
there  are  different  classes  of  phenomena,  which  attest  in  a  most 


CH.  VI.]  DENUDATION   OF    STRATIFIED   ROCKS. 


67 


Fig.  89. 


Valleys  of  denudation. 
a.  alluvium. 


striking  manner  the  vast  spaces  left  vacant  by  the  erosive  power  of 
water.  I  may  allude,  first,  to  those  valleys  on  both  sides  of  which 
the  same  strata  are  seen  following  each  other  in  the  same  order,  and 
having  the  same  mineral  composition  and  fossil  contents.  We  may 
observe,  for  example,  several  formations,  as  Nos.  1,  2,  3,  4,  in  the 
accompanying  diagram  (fig.  89.) ;  No.  1. 
conglomerate,  No.  2.  clay,  No.  3.  grit,  and 
No.  4.  limestone,  each  repeated  in  a  series 
of  hills  separated  by  valleys  varying  in 
depth.  When  we  examine  the  subordi- 
nate parts  of  these  four  formations,  we 
find,  in  like  manner,  distinct  beds  in  each, 
corresponding,  on  the  opposite  sides  of  the  valleys,  both  in  compo- 
sition and  order  of  position.  No  one  can  doubt  that  the  strata  were 
originally  continuous,  and  that  some  cause  has  swept  away  the  por- 
tions which  once  connected  the  whole  series.  A  torrent  on  the  side 
of  a  mountain  produces  similar  interruptions ;  and  when  we  make 
artificial  cuts  in  lowering  roads,  we  expose,  in  like  manner,  corre 
spending  beds  on  either  side.  But  in  nature,  these  appearances  occur 
in  mountains  several  thousand  feet  high,  and  separated  by  intervals 
of  many  miles  or  leagues  in  extent,  of  which  a  grand  exemplification 
is  described  by  Dr.  Macculloch,  on  the  north-western  coast  of  Ross- 
shire  in  Scotland.* 

Fig.  90. 
Suil  Veinn.  Coul  beg.  Coul  more. 


Denudation  of  red  sandstone  on  north-west  coast  of  Ross-shire.    (Macculloch.) 

The  fundamental  rock  of  that  country  is  gneiss,  in  disturbed  strata, 
on  which  beds  of  nearly  horizontal  red  sandstone  rest  un conformably. 
The  latter  are  often  very  thin,  forming  mere  flags,  with  their  surfaces, 
distinctly  ripple-marked.  They  end  abruptly  on  the  declivities  of 
many  insulated  mountains,  which  rise  up  at  once  to  the  height  of 
about  2000  feet  above  the  gneiss  of  the  surrounding  plain  or  table 
land,  and  to  an  average  elevation  of  about  3000  feet  above  the  sea, 
which  all  their  summits  generally  attain.  The  base  of  gneiss  varies 
in  height,  so  that  the  lower  portions  of  the  sandstone  occupy  different 
levels,  and  the  thickness  of  the  mass  is  various,  sometimes  exceeding 
3000  feet.  It  is  impossible  to  compare  these  scattered  and  detached 
portions  without  imagining  that  the  whole  country  has  once  been 
covered  with  a  great  body  of  sandstone,  and  that  masses  from  1000 
to  more  than  3000  feet  in  thickness  have  been  removed. 

In  the  "  Survey  of  Great  Britain  "  (vol.  i.),  Professor  Ramsay 
has  shown  that  the  missing  beds,  removed  from  the  summit  of  the 
Mendips,  must  have  been  nearly  a  mile  in  thickness ;  and  he  has 
pointed  out  considerable  areas  in  South  Wales  and  some  of  the  ad- 


*  Western  Islands,  vol.  ii.  p.  93.  pi.  31.  fig.  4. 
F  2 


68  DENUDATION  [Cn.  VI. 

jacent  counties  of  England,  where  a  series  of  primary  (or  palaeozoic) 
strata,  not  less  than  11,000  feet  in  thickness,  have  been  stripped  off. 
All  these  materials  have  of  course  been  transported  to  new  regions, 
and  have  entered  into  the  composition  of  more  modern  formations.  On 
the  other  hand,  it  is  shown  by  observations  in  the  same  "  Survey,"  that 
the  palaeozoic  strata  are  from  20,000  to  30,000  feet  thick.  It  is  clear 
that  such  rocks,  formed  of  mud  and  sand,  now  for  the  most  part 
consolidated,  are  the  monuments  of  denuding  operations,  which  took 
place  on  a  grand  scale  at  a  very  remote  period  in  the  earth's  history. 
For,  whatever  has  been  given  to  one  area  must  always  have  been 
borrowed  from  another ;  a  truth  which,  obvious  as  it  may  seem  when 
thus  stated,  must  be  repeatedly  impressed  on  the  student's  mind, 
because  in  many  geological  speculations  it  is  taken  for  granted  that 
the  external  crust  of  the  earth  has  been  always  growing  thicker  in 
consequence  of  the  accumulation,  period  after  period,  of  sedimentary 
matter,  as  if  the  new  strata  were  not  always  produced  at  the  expense 
of  pre-existing  rocks,  stratified  or  unstratified.  By  duly  reflecting 
on  the  fact,  that  all  deposits  of  mechanical  origin  imply  the  trans- 
portation from  some  other  region,  whether  contiguous  or  remote,  of 
an  equal  amount  of  solid  matter,  we  perceive  that  the  stony  exterior 
of  the  planet  must  always  have  grown  thinner  in  one  place,  whenever, 
by  accessions  of  new  strata,  it  was  acquiring  density  in  another.  No 
doubt  the  vacant  space  left  by  the  missing  rocks,  after  extensive 
denudation,  is  less  imposing  to  the  imagination  than  a  vast  thickness 
of  conglomerate  or  sandstone,  or  the  bodily  presence  as  it  were  of  a 
mountain-chain,  with  all  its  inclined  and  curved  strata.  But  the 
denuded  tracts  speak  a  clear  and  emphatic  language  to  our  reason, 
and,  like  repeated  layers  of  fossil  nummulites,  corals  or  shells,  or 
like  numerous  seams  of  coal,  each  based  on  its  under-clay  full  of  the 
roots  of  trees,  still  remaining  in  their  natural  position,  demand  an 
indefinite  lapse  of  time  for  their  elaboration. 

No  one  will  maintain  that  the  fossils  entombed  in  these  rocks  did 
not  belong  to  many  successive  generations  of  plants  and  animals. 
In  like  manner,  each  sedimentary  deposit  attests  a  slow  and  gradual 
action,  and  the  strata  not  only  serve  as  a  measure  of  the  amount 
of  denudation  simultaneously  effected  elsewhere,  but  are  also  a  cor- 
rect indication  of  the  rate  at  which  the  denuding  operation  was 
carried  on. 

Perhaps  the  most  convincing  evidence  of  denudation  on  a  mag- 
nificent scale  is  derived  from  the  levelled  surfaces  of  districts  where 
large  faults  occur.  I  have  shown,  in  fig.  87.  p.  63.,  and  in  fig.  91., 
how  angular  and  protruding  masses  of  rock  might  naturally  have 
been  looked  for  on  the  surface  immediately  above  great  faults,  al- 
though in  fact  they  rarely  exist.  This  phenomenon  may  be  well 
studied  in  those  districts  where  coal  has  been  extensively  worked,  for 
there  the  former  relation  of  the  beds  which  have  shifted  their  position 
niay  be  determined  with  great  accuracy.  Thus  in  the  coal  field  of 
Ashby  de  la  Zouch,  in  Leicestershire  (see  fig.  91.),  a  fault  occurs,  on 
one  side  of  which  the  coal  beds  abed  rise  to  the  height  of  500  feet 


Cn.  VI.] 


OF    STRATIFIED   ROCKS. 

Fig.  91. 


69 


Trr 


Faults  and  denuded  coal  strata,  Ashby  de  la  Zouch.    (Mammatt.) 

above  the  corresponding  beds  on  the  other  side.  But  the  uplifted 
strata  do  not  stand  up  500  feet  above  the  general  surface ;  on  the 
contrary,  the  outline  of  the  country,  as  expressed  by  the  line  z  z,  is 
uniformly  undulating  without  any  break,  and  the  mass  indicated  by 
the  dotted  outline  must  have  been  washed  away.*  There  are  proofs 
of  this  kind  in  some  level  countries,  where  dense  masses  of  strata 
have  been  cleared  away  from  areas  several  hundred  square  miles  in 
extent. 

In  the  Newcastle  coal  district  it  is  ascertained  that  faults  occur  in 
which  the  upward  or  downward  movement  could  not  have  been  less 
than  140  fathoms,  which,  had  they  affected  the  configuration  of  the 
surface  to  an  equal  amount,  would  produce  mountains  with  pre- 
cipitous escarpments  nearly  1000  feet  high,  or  chasms  of  the  like 
depth ;  yet  is  the  actual  level  of  the  country  absolutely  uniform, 
affording  no  trace  whatever  of  subterranean  movements.t 

The  ground  from  which  these  materials  have  been  removed  is 
usually  overspread  with  heaps  of  sand  and  gravel,  formed  out  of  the 
ruins  of  the  very  rocks  which  have  disappeared.  Thus,  in  the  dis- 
tricts above  referred  to,  they  consist  of  rounded  and  angular  frag- 
ments of  hard  sandstone,  limestone,  and  ironstone,  with  a  small 
quantity  of  the  more  destructible  shale,  and  even  rounded  pieces  of 
coal. 

Allusion  has  been  already  made  to  the  shattered  state  and  dis- 
cordant position  of  the  carboniferous  strata  in  Coalbrook  Dale 
(p.  62.).  The  collier  cannot  proceed  three  or  four  yards  without 
meeting  with  small  slips,  and  from  time  to  time  he  encounters  faults 
of  considerable  magnitude,  which  have  thrown  the  rocks  up  or 
down  several  hundred  feet.  Yet  the  superficial  inequalities  to  which 
these  dislocated  masses  originally  gave  rise  are  no  longer  discernible, 
and  the  comparative  flatness  of  the  existing  surface  can  only  be 
explained,  as  Mr.  Prestwich  has  observed,  by  supposing  the  frac- 
tured portions  to  have  been  removed  by  water.  It  is  also  clear  that 
strata  of  red  sandstone,  more  than  1000  feet  thick,  which  once 
covered  the  coal,  in  the  same  region,  have  been  carried  away  from 
large  areas.  That  water  has,  in  this  case,  been  the  denuding  agent, 
we  may  infer  from  the  fact  that  the  rocks  have  yielded  according  to 


*  See  Mammat's  Geological  Facts,  &c. 
p.  90.  and  plate. 


t  Conybeare's  Report  to  B:it.  Assoc. 
1842,  p.  381. 


F  3 


70  ORIGIN   OF   VALLEYS.  [Cn.  VI. 

their  different  degrees  of  hardness  ;  the  hard  trap  of  the  Wrekin,  for 
example,  and  other  hills,  having  resisted  more  than  the  softer  shale 
and  sandstone,  so  as  now  to  stand  out  in  bold  relief.  * 

Origin  of  valleys.  —  Many  of  the  earlier  geologists,  and  Dr.  Hutton 
among  them,  taught  that  "  rivers  have  in  general  hollowed  out  their 
valleys."  This  is  no  doubt  true  of  rivulets  and  torrents  which  are 
the  feeders  of  the  larger  streams,  and  which,  descending  over  rapid 
slopes,  are  most  subject  to  temporary  increase  and  diminution  in  the 
volume  of  their  waters.  It  must  also  be  admitted  that  the  quantity 
of  mud,'  sand,  and  pebbles  constituting  many  a  modern  delta  is  so 
considerable  as  to  prove  that  a  very  large  part  of  the  inequalities  now 
existing  on  the  earth's  surface  are  due  to  fluviatile  action ;  but 
the  principal  valleys  in  almost  every  great  hydrographical  basin  in 
the  world,  are  of  a  shape  and  magnitude  which  imply  that  they 
have  been  due  to  other  causes  besides  the  mere  excavating  power  of 
rivers. 

Some  geologists  have  imagined  that  a  deluge,  or  succession  of 
deluges,  may  have  been  the  chief  denuding  agency,  and  they  have 
speculated  on  a  series  of  enormous  waves  raised  by  the  instantaneous 
upthrow  of  continents  or  mountain  chains  out  of  the  sea.  But  even 
were  we  disposed  to  grant  such  sudden  upheavals  of  the  floor  of  the 
ocean,  and  to  assume  that  great  waves  would  be  the  consequence  of 
each  convulsion,  it  is  not  easy  to  explain  the  observed  phenomena  by 
the  aid  of  so  gratuitous  an  hypothesis. 

On  the  other  hand,  a  machinery  of  a  totally  different  kind  seems 
capable  of  giving  rise  to  effects  of  the  required  magnitude.  It  has 
now  been  ascertained  that  the  rising  and  sinking  of  extensive  por- 
tions of  the  earth's  crust,  whether  insensibly  or  by  a  repetition  of 
sudden  shocks,  is  part  of  the  actual  course  of  nature,  and  we  may 
easily  comprehend  how  the  land  may  have  been  exposed  during  these 
movements  to  abrasion  by  the  waves  of  the  sea.  In  the  same 
manner  as  a  mountain  mass  may,  in  the  course  of  ages,  be  formed 
by  sedimentary  deposition,  layer  after  layer,  so  masses  equally 
voluminous  may  in  time  waste  away  by  inches  ;  as,  for  example,  if 
beds  of  incoherent  materials  are  raised  slowly  in  an  open  sea  where 
a  strong  current  prevails.  It  is  well  known  that  some  of  these 
oceanic  currents  have  a  breadth  of  200  miles,  and  that  they  some- 
times run  for  a  thousand  miles  or  more  in  one  direction,  retaining  a 
considerable  velocity  even  at  the  depth  of  several  hundred  feet. 
Under  these  circumstances,  the  flowing  waters  may  have  power  to 
clear  away  each  stratum  of  incoherent  materials  as  it  rises  and 
approaches  the  surface,  where  the  waves  exert  the  greatest  force ; 
and  in  this  manner  a  voluminous  deposit  may  be  entirely  swept 
away,  so  that,  in  the  absence  of  faults,  no  evidence  may  remain  of 
the  denuding  operation.  It  may  indeed  be  affirmed  that  the  signs  of 
waste  will  usually  be  least  obvious  where  the  destruction  has  been 
most  complete ;  for  the  annihilation  may  have  proceeded  so  far,  that 
no  ruins  are  left  of  the  dilapidated  rocks. 

*  Frestwich,  Geol.  Trans,  second  series,  vol.  v.  pp.  452.  4?3. 


CH.  VI.]  INLAND   SEA-CLIFFS.  71 

Although  denudation  has  had  a  levelling  influence  on  some 
countries  of  shattered  and  disturbed  strata  (see  fig.  87.  p.  63.  and 
fig.  91.  p.  69.),  it  has  more  commonly  been  the  cause  of  superficial 
inequalities,  especially  in  regions  of  horizontal  stratification.  The 
general  outline  of  these  regions  is  that  of  flat  and  level  platforms, 
interrupted  by  valleys  often  of  considerable  depth,  and  ramifying 
in  various  directions.  These  hollows  may  once  have  formed  bays 
and  channels  between  islands,  and  the  steepest  slope  on  the  sides  of 
each  valley  may  have  been  a  sea-cliff",  which  was  undermined  for 
ages,  as  the  land  emerged  gradually  from  the  deep.  We  may 
suppose  the  position  and  course  of  each  valley  to  have  been  originally 
determined  by  differences  in  the  hardness  of  the  rocks,  and  by  rents 
and  joints  which  usually  occur  even  in  horizontal  strata.  In  moun- 
tain chains,  such  as  the  Jura  before  described  (see  fig.  71.  p.  55.), 
we  perceive  at  once  that  the  principal  valleys  have  not  been  due  to 
aqueous  excavation,  but  to  those  mechanical  movements  which  have 
bent  the  rocks  into  their  present  form.  Yet  even  in  the  Jura  there 
are  many  valleys,  such  as  C  (fig.  71.),  which  have  been  hollowed  out 
by  water ;  and  it  may  be  stated  that  in  every  part  of  the  globe  the 
unevenness  of  the  surface  of  the  land  has  been  due  to  the  combined 
influence  of  subterranean  movements  and  denudation. 

I  may  now  recapitulate  a  few  of  the  conclusions  to  which  we  have 
arrived:  first,  all  the  mechanical  strata  have  been  accumulated 
gradually,  and  the  concomitant  denudation  has  been  no  less  gradual : 
secondly,  the  dry  land  consists  in  great  part  of  strata  formed  origin- 
ally at  the  bottom  of  the  sea,  and  has  been  made  to  emerge  and 
attain  its  present  height  by  a  force  acting  from  beneath :  thirdly,  no 
combination  of  causes  has  yet  been  conceivedTso  capable  of  producing 
extensive  and  gradual  denudation,  as  the  action  of  the  waves  and 
currents  of  the  ocean  upon  land  slowly  rising  out  of  the  deep. 

Now,  if  we  adopt  these  conclusions,  we  shall  naturally  be  led  to 
look  everywhere  for  marks  of  the  former  residence  of  the  sea  upon 
the  land,  especially  near  the  coasts  from  which  the  last  retreat  of  the 
waters  took  place,  and  it  will  be  found  that  such  signs  are  not 
wanting. 

I  shall  have  occasion  to  speak  of  ancient  sea-cliffs,  now  far  inland, 
in  the  south-east  of  England,  when  treating  in  Chapter  XIX.  of  the 
denudation  of  the  chalk  in  Surrey,  Kent,  and  Sussex.  Lines  of 
upraised  sea-beaches  of  more  modern  date  are  traced,  at  various 
levels  from  20  to  100  feet  and  upwards  above  the  present  sea-level, 
for  great  distances  on  the  east  and  west  coasts  of  Scotland,  as  well  as 
in  Devonshire,  and  other  counties  in  England.  These  ancient  beach- 
lines  often  form  terraces  of  sand  and  gravel,  including  littoral  shells, 
some  broken,  others  entire,  and  corresponding  with  species  now- 
living  on  the  adjoining  coast.  But  it  would  be  unreasonable  to 
expect  to  meet  everywhere  with  the  signs  of  ancient  shores,  since  no 
geologist  can  have  failed  to  observe  how  soon  all  recent  marks  of  the 
kind  above  alluded  to  are  obscured  or  entirely  effaced,  wherever,  in 
consequence  of  the  altered  state  of  the  tides  and  currents,  the  sea  has 

F    4 


72  INLAND    SEA-CLIFFS.  [Cn.  VI. 

receded  for  a  few  centuries.  We  see  the  cliffs  crumble  down  in  a 
few  years  if  composed  of  sand  or  clay,  and  soon  reduced  to  a  gentle 
slope.  If  there  were  shells  on  the  beach,  they  decompose,  and  their 
materials  are  washed  away,  after  which  the  sand  and  shingle  may 
resemble  any  other  alluviums  scattered  over  the  interior. 

The  features  of  an  ancient  shore  may  sometimes  be  concealed  by 
the  growth  of  trees  and  shrubs,  or  by  a  covering  of  blown  sand,  a 
good  example  of  which  occurs  a  few  miles  west  from  Dax,  near 
Bourdeaux,  in  the  south  of  France.  About  twelve  miles  inland,  a 
steep  bank  may  be  traced  running  in  a  direction  nearly  north-east 
and  south-west,  or  parallel  to  the  contiguous  coast.  This  sudden 
fall  of  about  50  feet  conducts  us  from  the  higher  platform  of  the 
Landes  to  a  lower  plain  which  extends  to  the  sea.  The  outline  of 

Fig.  92. 


Section  of  inland  cliff  at  Abesse,  near  Dax. 
a.  Sand  of  the  Landes.  b.  Limestone.  c.  Clay. 

the  ground  suggested  to  me,  as  it  would  do  to  every  geologist,  the 
opinion  that  the  bank  in  question  was  once  a  sea-cliff,  when  the 
whole  country  stood  at  a  lower  level.  But  this  is  no  longer  matter 
of  conjecture,  for,  in  making  excavations  in  1830  for  the  foundation 
of  a  building  at  Abesse,  a  quantity  of  loose  sand,  which  formed  the 
slope  de,  was  removed;,  and  a  perpendicular  cliff,  about  50  feet  in 
height,  which  had  hitherto  been  protected  from  the  agency  of  the 
elements,  was  exposed.  At  the  bottom  appeared  the  limestone  b, 
containing  tertiary  shells  and  corals,  immediately  below  it  the  clay  c, 
and  above  it  the  usual  tertiary  sand  «,  of  the  department  of  the 
Landes.  At  the  base  of  the  precipice  were  seen  large  partially 
rounded  masses  of  rock,  evidently  detached  from  the  stratum  b. 
The  face  of  the  limestone  was  hollowed  out  and  weathered  into  such 
forms  as  are  seen  in  the  calcareous  cliffs  of  the  adjoining  coast, 
especially  at  Biaritz,  near  Bayonne.  It  is  evident  that,  when  this 
country  stood  at  a  somewhat  lower  level,  the  sea  advanced  along  the 
surface  of  the  argillaceous  stratum  c,  which,  from  its  yielding  nature, 
favoured  the  waste  by  allowing  the  more  solid  superincumbent  stone 
b  to  be  readily  undermined.  Afterwards,  when  the  country  had 
been  elevated,  part  of  the  sand,  a,  fell  down,  or  was  drifted  by  the 
winds,  so  as  to  form  the  talus,  d  e,  which  masked  the  inland  cliff  until 
it  was  artificially  laid  open  to  view. 

When  we  are  considering  the  various  causes  which,  in  the  course 
of  ages,  may  efface  the  characters  of  an  ancient  sea-coast,  earth- 
quakes must  not  be  forgotten.  During  violent  shocks,  steep  and 
overhanging  cliffs  are  often  thrown  down  and  become  a  heap  of 
ruins.  Sometimes  unequal  movements  of  upheaval  or  depression 


CH.  VI.]  INLAND    SEA-CLIFFS   AND   TERKACES.  73 

entirely  destroy  that  horizontality  of  the  base-line  which  constitutes 
the  chief  peculiarity  of  an  ancient  sea-cliff. 

It  is,  however,  in  countries  where  hard  limestone  rocks  abound, 
that  inland  cliffs  retain  faithfully  the  characters  which  they  acquired 
when  they  constituted  the  boundary  of  land  and  sea.  Thus,  in  the 
Morea,  no  less  than  three,  or  even  four,  ranges  of  what  were  once 
sea-cliffs  are  well  preserved.  These  have  been  described,  by  MM. 
Boblaye  and  Virlet,  as  rising  one  above  the  other  at  different  dis- 
tances from  the  actual  shore,  the  summit  of  the  highest  and  oldest 
occasionally  exceeding  1000  feet  in  elevation.  At  the  base  of  each 
there  is  usually  a  terrace,  which  is  in  some  places  a  few  yards,  in 
others  above  300  yards  wide,  so  that  we  are  conducted  from  the  high 
land  of  the  interior  to  the  sea  by  a  succession  of  great  steps.  These 
inland  cliffs  are  most  perfect,  and  most  exactly  resemble  those  now 
washed  by  the  waves  of  the  Mediterranean,  where  they  are  formed 
of  calcareous  rock,  especially  if  the  rock  be  a  hard  crystalline  marble. 
The  following  are  the  points  of  correspondence  observed  between  the 
ancient  coast  lines  and  the  borders  of  the  present  sea:  —  1.  A  range 
of  vertical  precipices,  with  a  terrace  at  their  base.  2.  A  weathered 
state  of  the  surface  of  the  naked  rock,  such  as  the  spray  of  the  sea 
produces.  3.  A  line  of  littoral  caverns  at  the  foot  of  the  cliffs.  4.  A 
consolidated  beach  or  breccia  with  occasional  marine  shells,  found  at 
the  base  of  the  cliffs,  or  in  the  caves.  5.  Lithodomous  perforations. 

In  regard  to  the  first  of  these,  it  would  be  superfluous  to  dwell  on 
the  evidence  afforded  of  the  undermining  power  of  waves  and  currents 
by  perpendicular  precipices.  The  littoral  caves,  also,  will  be  familiar 
to  those  who  have  had  opportunities  of  observing  the  manner  in 
which  the  waves  of  the  sea,  when  they  beat  against  rocks,  have 
power  to  scoop  out  caserns.  As  to  the  breccia,  it  is  composed  of 
pieces  of  limestone  and  rolled  fragments  of  thick  solid  shell,  such  as 
Strombus  and  Spondylus,  all  bound  together  by  a  crystalline  cal- 
careous cement.  Similar  aggregations  are  now  forming  on  the 
modern  beaches  of  Greece,  and  in  caverns  on  the  sea-side ;  and  they 
are  only  distinguishable  in  character  from  those  of  more  ancient 
date,  by  including  many  pieces  of  pottery.  In  regard  to  the  litho- 
domi  above  alluded  to,  these  bivalve  mollusks  are  well  known  to 
have  the  power  of  excavating  holes  in  the  hardest  limestones,  the 
size  of  the  cavity  keeping  pace  with  the  growth  of  the  shell.  When 
Hying  they  require  to  be  always  covered  by  salt  water,  but  similar 
pear-shaped  hollows,  containing  the  dead  shells  of  these  creatures, 
are  found  at  different  heights  on  the  face  of  the  inland  cliffs  above 
mentioned.  Thus,  for  example,  they  have  been  observed  near  Modon 
and  Navarino  on  cliffs  in  the  interior  125  feet  high  above  the  Medi- 
terranean. As  to  the  weathered  surface  of  the  calcareous  rocks,  all 
limestones  are  known  to  suffer  chemical  decomposition  when  moistened 
by  the  spray  of  the  salt  water,  and  are  corroded  still  more  deeply  at 
points  lower  down  where  they  are  just  reached  by  the  breakers.  By 
this  action  the  stone  acquires  a  wrinkled  and  furrowed  outline,  and 
very  near  the  sea  it  becomes  rough  and  branching,  as  if  covered  with 


74  INLAND   SEA-CLIFFS  [Cn.  VI. 

corals.  Such  effects  are  traced  not  only  on  the  present  shore,  but  at 
the  base  of  the  ancient  cliffs  far  in  the  interior.  Lastly,  it.  remains 
only  to  speak  of  the  terraces,  which  extend  with  a  gentle  slope  from 
the  base  of  almost  all  the  inland  cliffs,  and  are  for  the  most  part 
narrow  where  the  rock  is  hard,  but  sometimes  half  a  mile  or  more  in 
breadth  where  it  is  soft.  They  are  the  effects  of  the  encroachment 
of  the  ancient  sea  upon  the  shore  at  those  levels  at  which  the  land 
remained  for  a  long  time  stationary.  The  justness  of  this  view  is 
apparent  on  examining  the  shape  of  the  modern  shore  wherever  the 
sea  is  advancing  upon  the  land,  and  removing  annually  small 
portions  of  undermined  rock.  By  this  agency  a  submarine  platform 
is  produced  on  which  we  may  walk  for  some  distance  from  the  beach 
in  shallow  water,  the  increase  of  depth  being  very  gradual,  until  we 
reach  a  point  where  the  bottom  plunges  down  suddenly.  This  plat- 
form is  widened  with  more  or  less  rapidity  according  to  the  hardness 
of  the  rocks,  and  when  upraised  it  constitutes  an  inland  terrace. 

But  the  four  principal  lines  of  cliff  observed  in  the  Morea  do  not 
imply,  as  some  have  imagined,  four  great  eras  of  sudden  upheaval ; 
they  simply  indicate  the  intermittence  of  the  upheaving  force.  Had 
the  rise  of  the  land  been  continuous  and  uninterrupted,  there  would 
have  been  no  one  prominent  line  of  cliff;  for  every  portion  of  the 
surface  having  been,  in  its  turn,  and  for  an  equal  period  of  time,  a 
sea-shore,  would  have  presented  a  nearly  similar  aspect.  But  if 
pauses  occur  in  the  process  of  upheaval,  the  waves  and  currents  have 
time  to  sap,  throw  down,  and  clear  away  considerable  masses  of  rock, 
and  to  shape  out  at  several  successive  levels  lofty  ranges  of  cliffs 
with  broad  terraces  at  their  base. 

There  are  some  levelled  spaces,  however,  both  ancient  and  modern, 
in  the  Morea,  which  are  not  due  to  denudation,  although  resembling 
in  outline  the  terraces  above  described.  They  may  be  called  Terraces 
of  Deposition,  since  they  have  resulted  from  the  gain  of  land  upon 
the  sea  where  rivers  and  torrents  have  produced  deltas.  If  the  sedi- 
mentary matter  has  filled  up  a  bay  or  gulf  surrounded  by  steep 
mountains,  a  flat  plain  is  formed  skirting  the  inland  precipices  ;  and 
if  these  deposits  are  upraised,  they  form  a  feature  in  the  landscape 
very  similar  to  the  areas  of  denudation  before  described. 

In  the  island  of  Sicily  I  have  examined  many  inland  cliffs  like 
those  of  the  Morea ;  as,  for  example,  near  Palermo,  where  a  precipice 
is  seen  consisting  of  limestone  at  the  base  of  which  are  numerous 
caves.  One  of  these,  called  San  Ciro,  about  2  miles  distant  from 
Palermo,  is  about  20  feet  high,  10  wide,  and  180  above  the  sea. 
Within  it  is  found  an  ancient  beach  (b,  fig.  93.),  formed  of  pebbles 
of  various  rocks,  many  of  which  must  have  come  from  places  far 
remote.  Broken  pieces  of  coral  and  shell,  especially  of  oysters  and 
pectens,  are  seen  intermingled  with  the  pebbles.  Immediately  above 
the  level  of  this  beach,  serpulce  are  still  found  adhering  to  the  face  of 
the  rock,  and  the  limestone  is  perforated  by  lithodomi.  Within  the 
grotto,  also,  at  the  same  level,  similar  perforations  occur ;  and  so 
numerous  are  the  holes,  that  the  rock  is  compared  by  Hoffmann  to  a 


CH.  VI.]  IX   THE   ISLAND    OF    SICILY.  75 

target  pierced  by  musket  balls.     But  in  order  to  expose  to  view  these 

• 

Fig.  93. 


a.  Monte  Grifone.  .    b.  Cave  of  San  Ciro.» 

c.  Plain  of  Palermo,  in  which  are  Newer  Pliocene  strata  of 
limestone  and  sand.  d.  Bay  of  Palermo. 

marks  of  boring-shells  in  the  interior  of  the  cave,  it  was  necessary 
first  to  remove  a  mass  of  breccia,  which  consisted  of  numerous  frag- 
ments of  rock  and  an  immense  quantity  of  bones  of  the  mammoth, 
hippopotamus,  and  other  quadrupeds,  imbedded  in  a  dark  brown  cal- 
careous marl.  Many  of  the  bones  were  rolled  as  if  partially  subjected 
to  the  action  of  the  waves.  Below  this  breccia,  which  is  about  20 
feet  thick,  was  found  a  bed  of  sand  filled  with  sea-shells  of  recent 
species  ;  and  underneath  the  sand,  again,  is  the  secondary  limestone 
of  Monte  Grifone.  The  state  of  the  surface  of  the  limestone  in  the 
cave  above  the  level  of  the  marine  sand  is  very  different  from  that 
below  it.  Above,  the  rock  is  jagged  and  uneven,  as  is  usual  in  the 
roofs  and  sides  of  limestone  caverns  ;  below,  the  surface  is  smooth  and 
polished,  as  if  by  the  attrition  of  the  waves. 

The  platform  indicated  at  c,  fig.  93.,  is  formed  by  a  tertiary  de- 
posit containing  marine  shells  almost  all  of  -living  species,  and  it 
affords  an  illustration  of  the  terrace  of  deposition,  or  the  last  of  the 
two  kinds  before  mentioned  (p.  74.). 

There  are  also  numerous  instances  in  Sicily  of  terraces  of  denuda- 
tion. One  of  these  occurs  on  the  east  coast  to  the  north  of  Syracuse, 
and  the  same  is  resumed  to  the  south  beyond  the  town  of  Noto,  where 
it  may  be  traced  forming  a  continuous  and  lofty  precipice,  a  b,  fig.  94., 
facing  towards  the  sea,  and  constituting  the  abrupt  termination  of  a  cal- 
careous formation,  which  extends  in  horizontal  strata  far  inland.  This 
precipice  varies  in  height  from  500  to  700  feet,  and  between  its  base 
and  the  sea  is  an  inferior  platform,  c  b,  consisting  of  similar  white 
limestone.  All  the  beds  dip  towards  the  sea,  but  are  usually  inclined 
at  a  very  slight  angle :  they  are  seen  to  extend  uninterruptedly  from 
the  base  of  the  escarpment  into  the  platform,  showing  distinctly  that 
the  lofty  cliff  was  not  produced,  by  a  fault  or  vertical  shift  of  the 
beds,  but  by  the  removal  of  a  considerable  mass  of  rock.  Hence  we 
may  conclude  that  the  sea,  which  is  now  undermining  the  cliffs  of 
the  Sicilian  coast,  reached  at  some  former  period  the  base  of  the  pre- 
cipice a  b,  at  which  time  the  surface  of  the  terrace  c  b  must  have 


*  Section  given  by  Dr.  Christie,  Edin. 
New  Phil.  Journ.  No.  xxiil,  called  by 
mistake  the  Cave  of  Mardolce,  by  the 


late  M.  Hoffmann.  See  account  by  Mr. 
S.  P.  Pratt,  F.  G.  S.,  Proceedings  of  Geol. 
Soc.  No.  32.  1833. 


76 


INLAND   SEA-CLIFFS  AND 

Fig.  94. 


[Cn.  VI. 


f: ~! 


fe.. 


Sea 


been  covered  by  the  Mediterranean.  There  was  a  pause,  therefore, 
in  the  upward  movement,  when  the  waves  of  the  sea  had  time  to 
carve  out  the  platform  c  b ;  but  there  may  have  been  many  other 
stationary  periods  of  minor  duration.  Suppose,  for  example,  that  a 
series  of  escarpments  e,  /,  g,  h,  once  existed,  and  that  the  sea,  during 
a  long  interval  free  from  subterranean  movements,  advances  along 
the  line  c  b,  all  preceding  cliffs  must  have  been  swept  away  one  after 
the  other,  and  reduced  to  the  single  precipice  a  b. 

That  such  a  series  of  smaller  cliffs,  as  those  represented  at  e,  /,  g,  h, 
fig.  94.,  did  really  once  exist  at  intermediate  heights  in  place  of  the 
single  precipice  a  b,  is  rendered  highly  probable  by  the  fact,  that  in 
certain  bays  and  inland  valleys  opening  towards  the  east  coast  of 
Sicily,  and  not  far  from  the  section  given  in  fig.  94.,  the  solid  lime- 
stone is  shaped  out  into  a  great  succession  of  ledges,  separated  from 
each  other  by  small  vertical  cliffs.  These  are  sometimes  so  nume- 

Fig.  95. 


Valley  called  Gozzo  degli  Martiri,  below  Melilli,  Val  di  Noto. 

rous,  one  above  the  other,  that  where  there  is  a  bend  at  the  head  of  a 
valley,  they  produce  an  effect  singularly  resembling  the  seats  of  a 
Roman  amphitheatre.  A  good  example  of  this  configuration  occurs 
near  the  town  of  Melilli,  as  seen  in  the  annexed  view  (fig.  95.).  In 
the  south  of  the  island,  near  Spaccaforno  Scicli,  and  Modica,  preci- 


CH.  VI.]  TERRACES   IN   SICILY.  77 

pitous  rocks  of  white  limestone,  ascending  to  the  height  of  500  feet, 
have  been  carved  out  into  similar  forms. 

This  appearance  of  a  range  of  marble  seats  circling  round  the 
head  of  a  valley,  or  of  great  flights  of  steps  descending  from  the  top 
to  the  bottom,  on  the  opposite  sides  of  a  gorge,  may  be  accounted  for, 
as  already  hinted,  by  supposing  the  sea  to  have  stood  successively  at 
many  different  levels,  as  at  a  a,  b  b,  c  c,  in  the  accompanying  fig.  96. 
But  the  causes  of  the  gradual  contraction  of  the  valley  from  above 

Fig.  96. 


downwards  may  still  be  matter  of  speculation.  Such  contraction 
may  be  due  to  the  greater  force  exerted  by  the  waves  when  the  land 
at  its  first  emergence  was  smaller  in  quantity,  and  more  exposed  to 
denudation  in  an  open  sea  ;  whereas  the  wear  and  tear  of  the  rocks 
might  diminish  in  proportion  as  this  action  became  confined  within 
bays  or  channels  closed  in  on  two  or  three  sides.  Or,  secondly,  the 
separate  movements  of  elevation  may  have  followed  each  other  more 
rapidly  as  the  land  continued  to  rise,  so  that  the  times  of  those  pauses, 
during  which  the  greatest  denudation  was  accomplished  at  certain 
levels,  were  always  growing  shorter.  It  shQuld  be  remarked,  that 
the  cliffs  and  small  terraces  are  rarely  found  on  the  opposite  sides  of 
the  Sicilian  valleys  at  heights  so  precisely  answering  to  each  other  as 
those  given  in  fig.  96.,  and  this  might  have  been  expected,  to  which- 
ever of  the  two  hypotheses  above  explained  we  incline ;  for,  accord- 
ing to  the  direction  of  the  prevailing  winds  and  currents,  the  waves 
may  beat  with  unequal  force  on  different  parts  of  the  shore,  so  that 
while  no  impression  is  made  on  one  side  of  a  bay,  the  sea  may  en- 
croach so  far  on  the  other  as  to  unite  several  smaller  cliffs  into  one. 

Before  quitting  the  subject  of  ancient  sea-cliffs,  carved  out  of 
limestone,  I  shall  mention  the  range  of  precipitous  rocks,  composed 
of  a  white  marble  of  the  Oolitic  period,  which  I  hare  seen  near  the 
northern  gate  of  St.  Mihiel  in  France.  They  are  situated  on  the 
right  bank  of  the  Meuse,  at  a  distance  of  200  miles  from  the  nearest 
sea,  and  they  present  on  the  precipice  facing  the  river  three  or  four 
horizontal  grooves,  one  above  the  other,  precisely  resembling  those 
which  are  scooped  out  by  the  undermining  waves.  The  summits  of 
several  of  these  masses  are  detached  from  the  adjoining  hill,  in 
which  case  the  grooves  pass  all  round  them,  facing  towards  all  points 
of  the  compass,  as  if  they  had  once  formed  rocky  islets  near  the 
shore.* 

*  I  was  directed  by  M.  Deshayes  to  this  spot,  which  I  visited  in  June,  1833. 


78 


ROCKS   WORN   BY   THE    SEA. 


[On.  VI. 


Captain  Bayfield,  in  his  survey  of  the  Gulf  of  St.  Lawrence,  dis- 
covered in  several  places,  especially  in  the  Mingan  islands,  a  coun- 
terpart of  the  inland  cliffs  of  St.  Mihiel,  and  traced  a  succession  of 
shingle  beaches,  one  above  the  other,  which  agreed  in  their  level 
with  some  of  the  principal  grooves  scooped  out  of  the  limestone 
pillars.  These  beaches  consisted  of  calcareous  shingle,  with  shells  of 
recent  species,  the  farthest  from  the  shore  being  60  feet  above  the 
level  of  the  highest  tides.  In  addition  to  the  drawings  of  the  pillars 
called  the  flower-pots,  which  he  has  published*,  I  have  been  favoured 
with  other  views  of  rocks  on  the  same  coast,  drawn  by  Lieut.  A. 
Bowen,  K.N.  (See  fig.  97.) 

Fig.  97. 


Limestone  columns  in  Niapiscn  Island,  in  the  Gulf  of  St.  Lawrence.    Height 
oi  the  second  column  on  the  left,  60  feet. 

In  the  North-American  beaches  above  mentioned  rounded  frag- 
ments of  limestone  have  been  found  perforated  by  lithodomi;  and 
holes  drilled  by  the  same  mollusks  have  been  detected  in  the 
columnar  rocks  or  "flower-pots,"  showing  that  there  has  been  no 
great  amount  of  atmospheric  decomposition  on  the  surface,  or  the 
cavities  alluded  to  would  have  disappeared. 

We  have  an  opportunity  of  seeing  in  the  Bermuda  islands  the 

Fig.  98. 

A 


The  North  Rocks.  Bermuda,  lying  outside  the  great  coral  reef. 
A.  16  feet  high,  and  B.  12  feet.  c.  c.  Hollows  worn  by  the  sea. 

manner  in  which  the  waves  of  the  Atlantic  have  worn,  and  are  now 
wearing  out,  deep  smooth  hollows  on  every  side  of  projecting  masses 
of  hard  limestone.  In  the  annexed  drawing,  communicated  to  me 

*  See  Trans,  of  Geol.  Soc.,  second  series,  vol.  v.  plate  v. 


Cn.  VII.]  ALLUVIUM.  79 

by  Capt.  Nelson,  R.E.,  the  excavations  c,  c,  c,  have  been  scooped  out 
by  the  waves  in  a  stone  of  very  modern  date,  which,  although  ex- 
tremely hard,  is  full  of  recent  corals  and  shells,  some  of  which  retain 
their  colour. 

When  the  forms  of  these  horizontal  grooves,  of  which  the  surface 
is  sometimes  smooth  and  almost  polished,  and  the  roofs  of  which 
often  overhang  to  the  extent  of  5  feet  or  more,  have  been  care- 
fully studied  by  geologists,  they  will  serve  to  testify  the  former 
action  of  the  waves  at  innumerable  points  far  in  the  interior  of  the 
continents.  But  we  must  learn  to  distinguish  the  indentations  due 
to  the  original  action  of  the  sea,  and  those  caused  by  subsequent 
chemical  decomposition  of  calcareous  rocks,  to  which  they  are  liable 
in  the  atmosphere. 

I  shall  conclude  with  a  warning  to  beginners  not  to  feel  surprise 
if  they  can  detect  no  evidence  of  the  former  sojourn  of  the  sea  on 
lands  which  we  are  nevertheless  sure  have  been  submerged  at  periods 
comparatively  modern ;  for  notwithstanding  the  enduring  nature  of 
the  marks  left  by  littoral  action  on  calcareous  rocks,  we  can  by  no 
means  detect  sea-beaches  and  inland  cliffs  everywhere,  even  in  Sicily 
and  the  Morea.  On  the  contrary,  they  are,  upon  the  whole,  ex- 
tremely partial,  and  are  often  entirely  wanting  in  districts  composed 
of  argillaceous  and  sandy  formations,  which  must,  nevertheless,  have 
been  upheaved  at  the  same  time,  and  by  the  same  intermittent  move- 
ments, as  the  adjoining  calcareous  rocks. 


CHAPTER  VII. 

ALLUVIUM. 

Alluvium  described — Due  to  complicated  causes — Of  various  ages,  as  shown  in 
Auvergne — How  distinguished  from  rocks  in  situ — Kiver  terraces — Parallel 
roads  of  Glen  Koy — Various  theories  respecting  their  origin. 

BETWEEN  the  superficial  covering  of  vegetable  mould  and  the  sub- 
jacent rock  there  usually  intervenes  in  every  district  a  deposit  of 
loose  gravel,  sand,  and  mud,  to  which  the  name  of  alluvium  has 
been  applied.  The  term  is  derived  from  alluvio,  an  inundation,  or 
alluo,  to  wash,  because  the  pebbles  and  sand  commonly  resemble 
those  of  a  river's  bed  or  the  mud  and  gravel  washed  over  low  lands 
by  a  flood. 

A  partial  covering  of  such  alluvium  is  found  alike  in  all  climates, 
from  the  equatorial  to  the  polar  regions ;  but  in  the  higher  latitudes 
of  Europe  and  North  America  it  assumes  a  distinct  character,  being 
very  frequently  devoid  of  stratification,  and  containing  huge  frag- 
ments of  rock,  some  angular  and  others  rounded,  which  have  been 
transported  to  great  distances  from  their  parent  mountains.  When 
it  presents  itself  in  this  form,  it  has  been  called  "  diluvium,"  "  drift," 
or  the  "  boulder  formation ; "  and  its  probable  connexion  with  the 


80 


ALLUVIUM   IN  AUVERGNE. 


[Cn.  VII. 


agency  of  floating  ice  and  glaciers  will  be  treated  of  more  particularly 
in  the  eleventh  and  twelfth  chapters. 

The  student  will  be  prepared,  by  what  I  have  said  in  the  last 
chapter  on  denudation,  to  hear  that  loose  gravel  and  sand  are  often 
met  with,  not  only  on  the  low  grounds  bordering  rivers,  but  also  at 
various  points  on  the  sides  or  even  summits  of  mountains.  For,  in 
the  course  of  those  changes  in  physical  geography  which  may  take 
place  during  the  gradual  emergence  of  the  bottom  of  the  sea  and  its 
conversion  into  dry  land,  any  spot  may  either  have  been  a  sunken 
reef,  or  a  bay,  or  estuary,  or  sea-shore,  or  the  bed  of  a  river.  The 
drainage,  moreover,  may  have  been  deranged  again  and  again  by 
earthquakes,  during  which  temporary  lakes  are  caused  by  landslips, 
and  partial  deluges  occasioned  by  the  bursting  of  the  barriers  of  such 
lakes.  For  this  reason  it  would  be  unreasonable  to  hope  that  we 
should  ever  be  able  to  account  for  all  the  alluvial  phenomena  of  each 
particular  country,  seeing  that  the  causes  of  their  origin  are  so  various. 
Besides,  the  last  operations  of  water  have  a  tendency  to  disturb  and 
confound  together  all  pre-existing  alluviums.  Hence  we  are  always 
in  danger  of  regarding  as  the  work  of  a  single  era,  and  the  effect  of 
one  cause,  what  has  in  reality  been  the  result  of  a  variety  of  distinct 
agents,  during  a  long  succession  of  geological  epochs.  Much  useful 
instruction  may  therefore  be  gained  from  the  exploration  of  a  country 
like  Auvergne,  where  the  superficial  gravel  of  very  different  eras 
happens  to  have  been  preserved  by  sheets  of  lava,  which  were 
poured  out  one  after  the  other  at  periods  when  the  denudation,  and 
probably  the  upheaval,  of  rocks  were  in  progress.  That  region  had 
already  acquired  in  some  degree  its  present  configuration  before  any 
volcanoes  were  in  activity,  and  before  any  igneous  matter  was  super- 
imposed upon  the  granitic  and  fossiliferous  formations.  The  pebbles 
therefore  in  the  older  gravels  are  exclusively  constituted  of  granite 
and  other  aboriginal  rocks;  and  afterwards,  when  volcanic  vents 
burst  forth  into  eruption,  those  earlier  alluviums  were  covered  by 

Fig.  99. 


Lavas  of  Auvergne  resting  on  alluviums  of  different  ages. 

streams  of  lava,  which  protected  them  from  intermixture  with  gravel 
of  subsequent  date.  In  the  course  of  ages,  a  new  system  of  valleys 
was  excavated,  so  that  the  rivers  ran  at  lower  levels  than  those  at 
which  the  first  alluviums  and  sheets  of  lava  were  formed.  When, 
therefore,  fresh  eruptions  gave  rise  to  new  lava,  the  melted  matter 
was  poured  out  over  lower  grounds  ;  and  the  gravel  of  these  plains 


On.  VII.]  ALLUVIUM.  81 

differed  from  the  first  or  upland  alluvium,  by  containing  in  it  rounded 
fragments  of  various  volcanic  rocks,  and  often  bones  belonging  to 
distinct  groups  of  land  animals  which  flourished  in  the  country  in 
succession. 

The  annexed  drawing  will  explain  the  different  heights  at  which 
beds  of  lava  and  gravel,  each  distinct  from  the  other  in  composition 
and  age,  are  observed,  some  on  the  flat  tops  of  hills,  700  or  800  feet 
high,  others  on  the  slope  of  the  same  hills,  and  the  newest  of  all  in 
the  channel  of  the  existing  river  where  there  is  usually  gravel  alone, 
but  in  some  cases  a  narrow  stripe  of  solid  lava  sharing  the  bottom  of 
the  valley  with  the  river.  In  all  these  accumulations  of  transported 
matter  of  different  ages  the  bones  of  extinct  mammalia  have  been 
found  belonging  to  assemblages  of  land  quadrupeds,  which  flourished 
in  the  country  in  succession,  and  which  vary  specifically,  the  one  set 
from  the  other,  in  a  greater  or  less  degree,  in  proportion  as  the  time 
which  separated  their  entombment  has  been  more  or  less  protracted. 
The  streams  in  the  same  district  are  still  undermining  their  banks  and 
grinding  down  into  pebbles  or  sand,  columns  of  basalt  and  frag- 
ments of  granite  and  gneiss ;  but  portions  of  the  older  alluviums,  with 
the  fossil  remains  belonging  to  them,  are  prevented  from  being  mingled 
with  the  gravel  of  recent  date  by  the  cappings  of  lava  before  mentioned. 
But  for  the  accidental  interference,  therefore,  of  this  peculiar  cause, 
all  the  alluviums  might  have  passed  so  insensibly  the  one  into  the 
other,  that  those  formed  at  the  remotest  era  might  have  appeared 
of  the  same  date  as  the  newest,  and  the  whole  formation  might  have 
been  regarded  by  some  geologists  as  the  result  of  one  sudden  and 
violent  catastrophe. 

In  almost  every  country,  the  alluvium  consists  in  its  upper  part  of 
transported  materials,  but  it  often  passes  downwards  into  a  mass  of 
broken  and  angular  fragments  derived  from  the  subjacent  rock.  To 
this  mass  the  provincial  name  of  "  rubble,"  or  "  brash,"  is  given  in 
many  parts  of  England.  It  may  be  referred  to  the  weathering  or 
disintegration  of  stone  on  the  spot,  the  effects  of  air  and  water,  sun 
and  frost,  and  chemical  decomposition. 

The  inferior  surface  of  alluvial  deposits  is  often  very  irregular, 
conforming  to  all  the  inequalities  of  the  fundamental  rocks  (fig.  100.). 
Fig.  100.  Occasionally,    a    small    mass,    as   at   c, 

appears  detached,  and  as  if  included  in 
the  subjacent  formation.  Such  isolated 
portions  are  usually  sections  of  winding 
subterranean  hollows  filled  up  with  allu- 
vium. They  may  have  been  the  courses 
of  springs  or  subterranean  streamlets, 
which  have  flowed  through  and  enlarged 
natural  rents ;  or,  when  on  a  small  scale 
and  in  soft  strata,  they  may  be  spaces 
a.  vegetable  soil.  b.  Alluvium,  which  the  roots  of  large  trees  have  once 

c.  Mass  of  same,  apparently  detached.    occupiedj   gravel   and    gand   havin 

introduced  after  their  decay. 


82 


SAND-PIPES. 


[Cn.  VII. 


But  there  are  other  deep  hollows  of  a  cylindrical  form  found  in 
England,  France,  and  elsewhere,  penetrating  the  white  chalk,  and 
filled  with  sand  and  gravel,  which  are  not  so  readily  explained. 
They  are  sometimes  called  "  sand-pipes,"  or  "  sand-galls,"  and  "  puits 
naturels,"  in  France.  Those  represented  in  the  annexed  cut  were 


Fig.  101. 


Sand-pipes  in  the  chalk  at  Eaton,  near  Norwich. 

observed  by  me  in  1839,  laid  open  in  a  large  chalk-pit  near  Norwich. 
They  were  of  very  symmetrical  form,  the  largest  more  than  12  feet 
in  diameter,  and  some  of  them  had  been  traced,  by  boring,  to  the 
depth  of  more  than  60  feet.  The  smaller  ones  varied  from  a  few 
inches  to  a  foot  in  diameter,  and  seldom  descended  more  than  12  feet 
below  the  surface.  Even  where  three  of  them  occurred,  as  at  «, 
fig.  101.,  very  close  together,  the  parting  walls  of  soft  white  chalk 
were  not  broken  through.  They  all  taper  downwards  and  end  in  a 
point.  As  a  general  rule,  sand  and  pebbles  occupy  the  central  parts 
of  each  pipe,  while  the  sides  and  bottom  are  lined  with  clay. 

Mr.  Trimmer,  in  speaking  of  appearances  of  the  same  kind  in  the 
Kentish  chalk,  attributes  the  origin  of  such  "sand-galls"  to  the 
action  of  the  sea  on  a  beach  or  shoal,  where  the  waves,  charged 
with  shingle  and  sand,  not  only  wear  out  longitudinal  furrows,  such 
as  may  be  observed  on  the  surface  of  the  above-mentioned  chalk  near 
Norwich  when  the  incumbent  gravel  is  removed,  but  also  drill  deep 
circular  hollows  by  the  rotatory  motion  imparted  to  sand  and  pebbles. 
Such  furrows,  as  well  as  vertical  cavities,  are  now  formed,  he  observes, 
on  the  coast  where  the  shores  are  composed  of  chalk.* 

That  the  commencement  of  many  of  the  tubular  cavities  now  under 
consideration  has  been  due  to  the  cause  here  assigned,  I  have  little 
doubt.  But  such  mechanical  action  could  not  have  hollowed  out  the 
whole  of  the  sand-pipes  c  and  d,  fig.  101.,  because  several  large  chalk- 
flints  seen  protruding  from  the  walls  of  the  pipes  have  not  been 
eroded,  while  sand  and  gravel  have  penetrated  many  feet  below  them. 
In  other  cases,  as  at  bb,  similar  unrounded  nodules  of  flint,  still 
preserving  their  irregular  form  and  white  coating,  are  found  at 

*  Trimmer,  Proceedings  of  Geol.  Soc.  vol.  iv.  p.  7.  1842. 


Cn.  VII.]  ALLUVIUM.  83 

various  depths  in  the  midst  of  the  loose  materials  filling  the  pipe. 
These  have  evidently  been  detached  from  regular  layers  of  flints  oc- 
curring above.  It  is  also  to  be  remarked  that  the  course  of  the  same 
sand- pipe,  b  b,  is  traceable  above  the  level  of  the  chalk  for  some 
distance  upwards,  through  the  incumbent  gravel  and  sand,  by  the 
obliteration  of  all  signs  of  stratification.  Occasionally,  also,  as  in 
the  pipe  </,  the  overlying  beds  of  gravel  bend  downwards  into  the 
mouth  of  the  pipe,  so  as  to  become  in  parl  vertical,  as  would  happen 
if  horizontal  layers  had  sunk  gradually  in  consequence  of  a  failure  of 
support.  All  these  phenomena  may  be  accounted  for  by  attributing 
the  enlargement  and  deepening  of  the  sand-pipes  to  the  chemical 
action  of  water  charged  with  carbonic  acid,  derived  from  the  vegetable 
soil  and  the  decaying  roots  of  trees.  Such  acid  might  corrode  the 
chalk,  and  deepen  indefinitely  any  previously  existing  hollow,  but 
could  not  dissolve  the  flints.  The  water,  after  it  had  become  saturated 
with  carbonate  of  lime,  might  freely  percolate  the  surrounding  porous 
walls  of  chalk,  and  escape  through  them  and  from  the  bottom  of  the 
tube,  so  as  to  carry  away  in  the  course  of  time  large  masses  of 
dissolved  calcareous  rock  *,  and  leave  behind  it  on  the  edges  of  each 
tubular  hollow  a  coating  of  fine  clay,  which  the  white  chalk  contains. 

I  have  seen  tubes  precisely  similar  and  from  1  to  5  feet  in  diameter 
traversing  vertically  the  upper  half  of  the  soft  calcareous  building 
stone,  or  chalk  without  flints,  constituting  St.  Peter's  Mount,  Maes- 
tricht.  These  hollows  are  filled  with  pebbles  and  clay,  derived  from 
overlying  beds  of  gravel,  and  all  terminate  downwards  like  those 
of  Norfolk.  I  was  informed  that,  6  miles  from  Maestricht,  one  of 
these  pipes,  2  feet  in  diameter,  was  traced  dowiuvards  to  a  bed  of 
flattened  flints,  forming  an  almost  continuous  layer  in  the  chalk. 
Here  it  terminated  abruptly,  but  a  few  small  root-like  prolongations 
of  it  were  detected  immediately  below,  probably  where  the  dissolving 
substance  had  penetrated  at  some  points  through  openings  in  the 
siliceous  mass. 

It  is  not  so  easy  as  may  at  first  appear  to  draw  a  clear  line  of 
distinction  between  the  fixed  rocks,  or  regular  strata  (rocks  in  situ 
or  in  place),  and  alluvium.  If  the  bed  of  a  torrent  or  river  be  dried 
up,  we  call  the  gravel,  sand,  and  mud,  left  in  their  channels,  or 
whatever,  during  floods,  they  may  have  scattered  over  the  neighbour- 
ing plains,  alluvium.  The  very  same  materials  carried  into  a  lake, 
where  they  become  sorted  by  water  and  arranged  in  more  distinct 
layers,  especially  if  .they  inclose  the  remains  of  plants,  shells,  or  other 
fossils,  are  termed  regular  strata. 

In  like  manner  we  may  sometimes  compare  the  gravel,  sand,  and 
broken  shells,  strewed  along  the  path  of  a  rapid  marine  current,  with 
a  deposit  formed  contemporaneously  by  the  discharge  of  similar  ma- 
terials year  after  year,  into  a  deeper  and  more  tranquil  part  of  the 
sea.  In  such  cases,  when  we  detect  marine  shells  or  other  organic 
remains  entombed  in  the  strata  which  enable  us  to  determine  their 

*  See  Lyell  on  Sand-pipes,  &c.,  Phil  Mag.,  third  series,  vol.  xv.  p.  257.,  Oct.  1839, 

G  2 


84  ALLUVIUM.  [Cn.  VII. 

age  and  mode  of  origin,  we  regard  them  as  part  of  the  regular  series 
of  fossiliferous  formations,  whereas,  if  there  are  no  fossils,  we  have 
frequently  no  power  of  separating  them  from  the  general  mass  of 
superficial  alluvium. 

The  usual  rarity  of  organic  remains  in  beds  of  loose  gravel  is  partly 
owing  to  the  friction  which  originally  ground  down  rocks  into  pebbles, 
or  sand,  and  organic  bodies  into  small  fragments,  and  it  is  partly  owing 
to  the  porous  nature  of  alluvium  when  it  has  emerged,  which  allows 
the  free  percolation  through  it  of  rain-water,  and  promotes  the  de- 
composition and  solution  of  fossil  remains. 

It  has  long  been  a  matter  of  common  observation  that  most  rivers 
are  now  cutting  their  channels  through  alluvial  deposits  of  greater 
depth  and  extent  than  could  ever  have  been  formed  by  the  present 
streams.  From  this  fact  a  rash  inference  has  sometimes  been  drawn, 
that  rivers  in  general  have  grown  smaller,  or  become  less  liable  to  be 
flooded  than  formerly.  But  such  phenomena  would  be  a  natural  result 
of  considerable  oscillations  in  the  level  of  the  land  experienced  since 
the  existing  valleys  originated. 

Suppose  part  of  a  continent,  comprising  within  it  a  large  hydro- 
graphical  basin  like  that  of  the  Mississippi,  to  subside  several  inches 
or  feet  in  a  century,  as  the  west  coast  of  Greenland,  extending  600 
miles  north  and  south,  has  been  sinking  for  three  or  four  centuries, 
between  the  latitudes  60°  and  69°  N.  *  It  will  rarely  happen  that 
the  rate  of  subsidence  will  be  everywhere  equal,  and  in  many  cases 
the  amount  of  depression  in  the  interior  will  regularly  exceed  that  of 
the  region  nearer  the  sea.  Whenever  this  happens,  the  fall  of  the 
waters  flowing  from  the  upland  country  will  be  diminished,  and  each 
tributary  stream  will  have  less  power  to  carry  its  sand  and  sediment 
into  the  main  river,  and  the  main  river  less  power  to  convey  its 
annual  burden  of  transported  matter  to  the  sea.  All  the  rivers,  there- 
fore, will  proceed  to  fill  up  partially  their  ancient  channels,  and, 
during  frequent  inundations,  will  raise  their  alluvial  plains  by  new 
deposits.  If  then  the  same  area  of  land  be  again  upheaved  to  its 
former  height,  the  fall,  and  consequently  the  velocity,  of  every  river 
will  begin  to  augment.  Each  of  them  will  be  less  given  to  overflow 
its  alluvial  plain ;  and  their  power  of  carrying  earthy  matter  sea- 
ward, and  of  scouring  out  and  deepening  their  channels,  will  be 
sustained  till,  after  a  lapse  of  many  thousand  years,  each  of  them 
has  eroded  a  new  channel  or  valley  through  a  fluviatile  formation 
of  comparatively  modern  date.  The  surface  of  what  was  once  the 
river-plain  at  the  period  of  greatest  depression,  will  then  remain  fring- 
ing the  valley-sides  in  the  form  of  a  terrace  apparently  flat,  but  in 
reality  sloping  down  with  the  general  inclination  of  the  river.  Every- 
where this  terrace  will  present  cliffs  of  gravel  and  sand,  facing  the 
river.  That  such  a  series  of  movements  has  actually  taken  place  in  the 
main  valley  of  the  Mississippi  and  in  its  tributary  valleys  during  oscil- 
lations of  level,  I  have  endeavoured  to  show  in  my  description  of  that 

»  Principles  of  Geology,  7th  ed.  p.  506.,  8th  ed.  p.  509. 


CH.  VII.]  RIVER    TERRACES.  85 

country  *  ;  and  the  freshwater  shells  of  existing  species  and  bones  of 
land  quadrupeds,  partly  of  extinct  races,  preserved  in  the  terraces  of 
fluviatile  origin,  attest  the  exclusion  of  the  sea  during  the  whole  pro- 
cess of  filling  up  and  partial  re-excavation. 

In  many  cases,  the  alluvium  in  which  rivers  are  now  cutting  their 
channels,  originated  when  the  land  first  rose  out  of  the  sea.  If, 
for  example,  the  emergence  was  caused  by  a  gradual  and  uniform 
motion,  every  bay  and  estuary,  or  the  straits  between  islands,  would 
dry  up  slowly,  and  during  their  conversion  into  valleys,  every  part 
of  the  upheaved  area  would  in  its  turn  be  a  sea-shore,  and  might  be 
strewed  over  with  littoral  sand  and  pebbles,  or  each  spot  might  be 
the  point  where  a  delta  accumulated  during  the  retreat  and  exclusion 
of  the  sea.  Materials  so  accumulated  would  conform  to  the  general 
slope  of  a  valley  from  its  head  to  the  sea-coast. 

River  terraces.  —  We  often  observe  at  a  short  distance  from  the 
present  bed  of  a  river  a  steep  cliff  a  few  feet  or  yards  high,  and  on  a 
level  with  the  top  of  it  a  flat  terrace  corresponding  in  appearance  to 
the  alluvial  plain  which  immediately  borders  the  river.  This  terrace 
is  again  bounded  by  another  cliff,  above  which  a  second  terrace 
sometimes  occurs  ;  and  in  this  manner  two  or  three  ranges  of  cliffs 
and  terraces  are  occasionally  seen  on  one  or  both  sides  of  the  stream, 
the  number  varying,  but  those  on  the  opposite  sides  often  corre- 
sponding in  height. 

Fig.  102. 


River  Terraces  and  Parallel  Roads. 

These  terraces  are  seldom  continuous  for  great  distances,  and  their 
surface  slopes  downwards  with  an  inclination  similar  to  that  of  the 
river.  They  are  readily  explained  if  we  adopt  the  hypothesis  before 
suggested,  of  a  gradual  rise  of  the  land ;  especially  if,  while  rivers  are 
shaping  out  their  beds,  the  upheaving  movement  be  intermittent,  so 
that  long  pauses  shall  occur,  during  which  the  stream  will  have  time 
to  encroach  upon  one  of  its  banks,  so  as  to  clear  away  and  flatten  a 
large  space.  This  operation  being  afterwards  repeated  at  lower 
levels,  there  will  be  several  successive  cliffs  and  terraces. 


*  Second  Visit  to  the  U.  S.  vol.  ii.  chap.  34. 
o  3 


86  PARALLEL   EOADS  [Cn.  VII. 

Parallel  roads.  —  The  parallel  shelves,  or  roads,  as  they  have  been 
called,  of  Lochaber  or  Glen  Roy  and  other  contiguous  valleys  in 
Scotland,  are  distinct  both  in  character  and  origin  from  the  terraces 
above  described;  for  they  have  no  slope  towards  the  sea  like  the 
channel  of  a  river,  nor  are  they  the  effect  of  denudation.  Glen 
Roy  is  situated  in  the  Western  Highlands,  about  ten  miles  north  of 
Fort  William,  near  the  western  end  of  the  great  glen  of  Scotland,  or 
Caledonian  Canal,  and  near  the  foot  of  the  highest  of  the  Grampians, 
Ben  Nevis.  Throughout  its  .whole  length,  a  distance  of  more  than 
ten  miles,  two,  and  in  its  lower  part  three,  parallel  roads  or  shelves 
are  traced  along  the  steep  sides  of  the  mountains,  as  represented  in 
the  annexed  figure,  fig.  102.,  each  maintaining  a  perfect  horizontality, 
and  continuing  at  exactly  the  same  level  on  the  opposite  sides  of  the 
glen.  Seen  at  a  distance,  they  appear  like  ledges  or  roads,  cut  arti- 
ficially out  of  the  sides  of  the  hills  ;  but  when  we  are  upon  them  we 
can  scarcely  recognize  their  existence,  so  uneven  is  their  surface, 
and  so  covered  with  boulders.  They  are  from  10  to  60  feet  broad, 
and  merely  differ  from  the  side  of  the  mountain  by  being  somewhac 
less  steep. 

On  closer  inspection,  we  find  that  these  terraces  are  stratified  in 
the  ordinary  manner  of  alluvial  or  littoral  deposits,  as  may  be  seen  at 
those  points  where  ravines  have  been  excavated  by  torrents.  The 
parallel  shelves,  therefore,  have  not  been  caused  by  denudation,  but 
by  the  deposition  of  detritus,  precisely  similar  to  that  which  is  dis- 
persed in  smaller  quantities  over  the  declivities  of  the  hills  above. 
These  hills  consist  of  clay-slate,  mica-schist,  and  granite,  which  rocks 
have  been  worn  away  and  laid  bare  at  a  few  points  only,  in  a  line 
just  above  the  parallel  roads.  The  highest  of  these  roads  is  about 
1250  feet  above  the  level  of  the  sea,  the  next  about  200  feet  lower 
than  the  uppermost,  and  the  third  still  lower  by  about  50  feet.  It  is 
only  this  last,  or  the  lowest  of  the  three,  which  is  continued  through- 
out Glen  Spean,  a  large  valley  with  which  Glen  Roy  unites.  As 
the  shelves  are  always  at  the  same  height  above  the  sea,  they  become 
continually  more  elevated  above  the  river  in  proportion  as  we  descend 
each  valley;  and  they  at  length  terminate  very  abruptly,  without 
any  obvious  cause,  or  any  change  either  in  the  shape  of  the  ground 
or  in  the  composition  or  hardness  of  the  rocks.  I  should  exceed  the 
limits  of  this  work,  were  I  to  attempt  to  give  a  full  description  of  all 
the  geographical  circumstances  attending  these  singular  terraces,  or 
to  discuss  the  ingenious  theories  which  have  been  severally  proposed 
to  account  for  them  by  Dr.  Macculloch,  Sir  T.  D.  Lauder,  and  Messrs. 
Darwin,  Agassiz,  Milne,  and  Chambers.  There  is  one  point,  how- 
ever, on  which  all  are  agreed,  namely,  that  these  shelves  are  ancient 
beaches,  or  littoral  formations  accumulated  round  the  edges  of  one  or 
more  sheets  of  water  which  once  stood  at  the  level,  first  of  the 
highest  shelf,  and  successively  at  the  height  of  the  two  others.  It  is 
well  known,  that  wherever  a  lake  or  marine  fiord  exists  surrounded 
by  steep  mountains  subject  to  disintegration  by  frost  or  the  action 
of  torrents,  some  loose  matter  is  washed  down  annually,  especially 


CH.  VIL]  OF  GLEN  EOT.  87 

during  the  melting  of  snow,  and  a  check  is  given  to  the  descent  of 
this  detritus  at  the  point  where  it  reaches 
the  waters  of  the  lake.  The  waves  then 
spread  out  the  materials  along  the  shore, 
and  throw  some  of  them  upon  the  beach ; 
their  dispersing  power  being  aided  by  the 
ice,  which  often  adheres  to  pebbles  during 
the  winter  months,  and  gives  buoyancy  to 
them.  The  annexed  diagram  illustrates 
the  manner  in  which  Dr.  Macculloch  and 
Mr.  Darwin  suppose  "  the  roads  "  to  con- 
stitute mere  indentations  in  a  superficial 
A  B.  supposed  original  surface  of  alluvial  coating  which  rests  upon  the  hill- 
c T)Ck'RoadS  or  shelves  in  the  outer  side,  and  consists  chiefly  of  clay  and  sharp 

unrounded  stones. 

Among  other  proofs  that  the  parallel  roads  have  really  been  formed 
along  the  margin  of  a  sheet  of  water,  it  may  be  mentioned,  that 
wherever  an  isolated  hill  rises  in  the  middle  of  the  glen  above  the 
level  of  any  particular  shelf,  a  corresponding  shelf  is  seen  at  the 
same  level  passing  round  the  hill,  as  would  have  happened  if  it  had 
once  formed  an  island  in  a  lake  or  fiord.  Another  very  remarkable 
peculiarity  in  these  terraces  is  this;  each  of  them  comes  in  some 
portion  of  its  course  to  a  col,  or  passage  between  the  heads  of  glens, 
the  explanation  of  which  will  be  considered  in  the  sequel. 

Those  writers  who  first  advocated  the  doctrine  that  the  roads  were 
the  ancient  beaches  of  freshwater  lakes,  were  unable  to  offer  any 
probable  hypothesis  respecting  the  formation  and  subsequent  removal 
of  barriers  of  sufficient  height  and  solidity  to  jdam  up  the  water.  To 
introduce  any  violent  convulsion  for  their  removal  was  inconsistent 
with  the  uninterrupted  horizontality  of  the  roads,  and  with  the 
undisturbed  aspect  of  those  parts  of  the  glens  where  the  shelves 
come  suddenly  to  an  end.  Mr.  Agassiz  and  Dr.  Buckland,  desirous, 
like  the  defenders  of  the  lake  theory,  to  account  for  the  limitation  of 
the  shelves  to  certain  glens,  and  their  absence  in  contiguous  glens, 
where  the  rocks  are  of  the  same  composition,  and  the  slope  and 
inclination  of  the  ground  very  similar,  started  the  conjecture  that 
these  valleys  were  once  blocked  up  by  enormous  glaciers  descending 
from  Ben  Nevis,  giving  rise  to  what  are  called  in  Switzerland  and  in 
the  Tyrol,  glacier-lakes.  After  a  time  the  icy  barrier  was  broken 
down,  or  melted,  first,  to  the  level  of  the  second,  and  afterwards  to 
that  of  the  third  road  or  shelf. 

In  corroboration  of  this  view,  they  contended  that  the  alluvium  of 
Glen  Roy,  as  well  as  of  other  parts  of  Scotland,  agrees  in  character 
with  the  moraines  of  glaciers  seen  in  the  Alpine  valleys  of  Switzer- 
land. Allusion  will  be  made  in  the  eleventh  chapter  to  the  former 
existence  of  glaciers  in  the  Grampians :  in  the  mean  time  it  will 
readily  be  conceded  that  this  hypothesis  is  preferable  to  any  pre- 
vious lacustrine  theory,  by  accounting  more  easily  for  the  temporary 
existence  and  entire  disappearance  of  lofty  transverse  barriers,  al- 

G  4 


88  PARALLEL    ROADS    OF    GLEN    ROY.  [Cn.  VII. 

though  the  height  required  for  the  imaginary  dams  of  ice  may  be 
startling. 

Before  the  idea  last  alluded  to  had  been  entertained,  Mr.  Darwin 
examined  Glen  Roy,  and  came  to  the  opinion  that  the  shelves  were 
formed  when  the  glens  were  still  arms  of  the  sea,  and,  consequently, 
that  there  never  were  any  seaward  barriers.  According  to  him,  the 
land  emerged  during  a  slow  and  uniform  upward  movement,  like  that 
now  experienced  throughout  a  large  part  of  Sweden  and  Finland ;  but 
there  were  certain  pauses  in  the  upheaving  process,  at  which  times 
the  waters  of  the  sea  remained  stationary  for  so  many  centuries  as  to 
allow  of  the  accumulation  of  an  extraordinary  quantity  of  detrital 
matter,  and  the  excavation,  at  many  points  immediately  above,  of 
deep  notches  and  bare  cliffs  in  the  hard  and  solid  rock. 

The  phenomena  which  are  most  difficult  to  reconcile  with  this 
theory  are,  first,  the  abrupt  cessation  of  the  roads  at  certain  points 
in  the  different  glens ;  secondly,  their  unequal  number  in  different 
valleys  connecting  with  each  other,  there  being  three,  for  example, 
in  Glen  Roy  and  only  one  in  Glen  Spean  ;  thirdly,  the  precise  hori- 
zontality  of  level  maintained  by  the  same  shelf  over  a  space  many 
leagues  in  length  requiring  us  to  assume,  that  during  a  rise  of  1250 
feet  no  one  portion  of  the  land  was  raised  even  a  few  yards  above 
another ;  fourthly,  the  coincidence  of  level  already  alluded  to  of  each 
shelf  with  a  col,  or  the  point  forming  the  head  of  two  glens,  from 
which  the  rain-waters  flow  in  opposite  directions.  This  last-men- 
tioned feature  in  the  physical  geography  of  Lochaber  seems  to  have 
been  explained  in  a  satisfactory  manner  by  Mr.  Darwin.  He  calls 
these  cols  "  landstraits,"  and  regards  them  as  having  been  anciently 
sounds  or  channels  between  islands.  He  points  out  that  there  is  a 
tendency  in  such  sounds  to  be  silted  up,  and  always  the  more  so  in 
proportion  to  their  narrowness.  In  a  chart  of  the  Falkland  Islands, 
by  Capt.  Sullivan,  R.  N.,  it  appears  that  there  are  several  examples 
there  of  straits  where  the  soundings  diminish  regularly  towards  the 
narrowest  part.  One  is  so  nearly  dry  that  it  can  be  walked  over  at 
low  water,  and  another,  no  longer  covered  by  the  sea,  is  supposed  to 
have  recently  dried  up  in  consequence  of  a  small  alteration  in  the  re- 
lative level  of  sea  and  land.  "  Similar  straits,"  observes  Mr.  Chambers, 
"  hovering,  in  character,  between  sea  and  land,  and  which  may  be 
called  fords,  are  met  with  in  the  Hebrides.  Such,  for  example,  is  the 
passage  dividing  the  islands  of  Lewis  and  Harris,  and  that  between 
North  Uist  and  Benbecula,  both  of  which  would  undoubtedly  appear 
as  cols,  coinciding  with  a  terrace  or  raised  beach,  all  round  the  islands, 
if  the  sea  were  to  subside."* 

The  first  of  the  difficulties  above  alluded  to,  namely,  the  non-exten- 
sion of  the  shelves  over  certain  parts  of  the  glens,  may  be  explained, 
as  Mr.  Darwin  suggests,  by  supposing  in  certain  places  a  quick  growth 
of  green  turf  on  a  good  soil,  which  prevented  the  rain  from  washing 
away  any  loose  materials  lying  on  the  surface.  But  wherever  the 
soil  was  barren,  and  where  green  sward  took  long  to  form,  there  may 

*  "  Ancient  Sea  Margins,"  p.  114.,  by  K.  Chambers. 


CH.  VII.]  CHRONOLOGY   OF    ROCKS. 

have  been  time  for  the  removal  of  the  gravel.  In  one  case  an  inter- 
mediate shelf  appears  for  a  short  distance  (three  quarters  of  a  mile)  on 
the  face  of  the  mountain  called  Tombhran,  between  the  two  upper 
shelves,  and  is  seen  nowhere  else.  It  occurs  where  there  was  the  longest 
space  of  open  water,  and  where,  perhaps,  the  waves  acquired  a  greater 
than  ordinary  power  in  heaping  up  detritus. 

Next  as  to  the  precise  horizontality  of  level  maintained  by  the 
parallel  roads  of  Lochaber  over  an  area  many  leagues  in  length  and 
breadth,  this  is  a  difficulty  common  in  some  degree  to  all  the  rival 
hypotheses,  whether  of  lakes,  or  glaciers,  or  of  the  simple  upheaval 
of  the  land  above  the  sea.  For  we  cannot  suppose  the  roads  to  be 
more  ancient  than  the  glacial  period,  or  the  era  of  the  boulder  form- 
ation of  Scotland,  of  which  I  shall  speak  in  the  eleventh  and  twelfth 
chapters.  Strata  of  that  era  of  marine  origin  containing  northern 
shells  of  existing  species  have  been  found  at  various  heights  in 
Scotland,  some  on  the  east,  and  others  on  the  west  coast,  from  20  to 
400  feet  high ;  and  in  one  region  in  Lanarkshire  not  less  than  524 
feet  above  high-water  mark.  It  seems,  therefore,  in  the  highest  degree 
improbable  that  Glen  Roy  should  have  escaped  entirely  the  upward 
movement  experienced  in  so  many  surrounding  regions, — a  movement 
implied  by  the  position  of  these  marine  deposits,  in  which  the  shells 
are  almost  all  of  known  recent  species.  But  if  the  motion  has  really 
extended  to  Glen  Roy  and  the  contiguous  glens,  it  must  have  up- 
lifted them  bodily,  without  in  the  slightest  degree  affecting  their 
horizontality ;  and  this  being  admitted,  the  principal  objection  to  the 
theory  of  marine  beaches,  founded  on  the  uniformity  of  upheaval,  is 
removed,  or  is  at  least  common  to  every  theory  hitherto  proposed. 

To  assume  that  the  ocean  has  gone  down  from  the  level  of  the 
uppermost  shelf,  or  1250  feet,  simultaneously  all  over  the  globe, 
while  the  land  remained  unmoved,  is  a  view  which  will  find  favour 
with  very  few  geologists,  for  the  reasons  explained  in  the  fifth  chapter. 

The  student  will  perceive,  from  the  above  sketch  of  the  controversy 
respecting  the  formation  of  these  curious  shelves,  that  this  problem, 
like  many  others  in  geology,  is  as  yet  only  solved  in  part ;  and  that  a 
larger  number  of  facts  must  be  collected  and  reasoned  upon  before 
the  question  can  be  finally  settled. 


90  CHRONOLOGY   OF    ROCKS.  [Cn.  VIII. 


CHAPTER  VIII. 

CHRONOLOGICAL  CLASSIFICATION  OP  ROCKS. 

Aqueous,  plutonic,  volcanic,  and  metamorphic  rocks,  considered  chronologically — 
Lehman's  division  into  primitive  and  secondary — Werner's  addition  of  a  tran- 
sition class — Neptunian  theory  —  Button  on  igneous  origin  of  granite — How 
the  name  of  primary  was  still  retained  for  granite —  The  term  "  transition,"  why 
faulty — The  adherence  to  the  old  chronological  nomenclature  retarded  the 
progress  of  geology — New  hypothesis  invented  to  reconcile  the  igneous  origin 
of  granite  to  the  notion  of  its  high  antiquity — Explanation  of  the  chronological 
nomenclature  adopted  in  this  work,  so  far  as  regards  primary,  secondary,  and 
tertiary  periods. 

IN  the  first  chapter  it  was  stated  that  the  four  great  classes  of  rocks, 
the  aqueous,  the  volcanic,  the  plutonic,  and  the  metamorphic,  would 
each  be  considered  not  only  in  reference  to  their  mineral  characters, 
and  mode  of  origin,  but  also  to  their  relative  age.  In  regard  to  the 
aqueous  rocks,  we  have  already  seen  that  they  are  stratified,  that 
some  are  calcareous,  others  argillaceous  or  siliceous,  some  made  up 
of  sand,  others  of  pebbles;  that  some  contain  freshwater,  others 
marine  fossils,  and  so  forth ;  but  the  student  has  still  to  learn  which 
rocks,  exhibiting  some  or  all  of  these  characters,  have  originated  at 
one  period  of  the  earth's  history,  and  which  at  another. 

To  determine  this  point  in  reference  to  the  fossiliferous  formations 
is  more  easy  than  in  any  other  class,  and  it  is  therefore  the  most  con- 
venient and  natural  method  to  begin  by  establishing  a  chronology  for 
these  strata,  and  then  to  refer  as  far  as  possible  to  the  same  divisions, 
the  several  groups  of  plutonic,  volcanic,  and  metamorphic  rocks. 
Such  a  system  of  classification  is  not  only  recommended  by  its  greater 
clearness  and  facility  of  application,  but  is  also  best  fitted  to  strike 
the  imagination  by  bringing  into  one  view  the  contemporaneous  rero- 
lutions  of  the  inorganic  and  organic  creations  of  former  times.  For 
the  sedimentary  formations  are  most  readily  distinguished  by  the 
different  species  of  fossil  animals  and, plants  which  they  inclose, 
and  of  which  one  assemblage  after  another  has  flourished  and  then 
disappeared  from  the  earth  in  succession. 

But  before  entering  specially  on  the  subdivisions  of  the  aqueous 
rocks  arranged  according  to  the  order  of  time,  it  will  be  desirable  to 
say  a  few  words  on  the  chronology  of  rocks  in  general,  although  in 
doing  so  we  shall  be  unavoidably  led  to  allude  to  some  classes  of 
phenomena  which  the  beginner  must  not  yet  expect  fully  to  com- 
prehend. 

It  was  for  many  years  a  received  opinion  that  the  formation  of 
entire  families  of  rocks,  such  as  the  plutonic  and  those  crystalline 
schists  spoken  of  in  the  first  chapter  as  metamorphic,  began  and 
ended  before  any  members  of  the  aqueous  and  volcanic  orders  were 


OH.  VIII.]  CLASSIFICATION   OF   KOCKS.  91 

produced;  and  although  this  idea  has  long  been  modified,  and  is 
nearly  exploded,  it  will  be  necessary  to  give  some  account  of  the 
ancient  doctrine,  in  order  that  beginners  may  understand  whence 
many  prevailing  opinions,  and  some  part  of  the  nomenclature  of 
geology,  still  partially  in  use,  was  derived. 

About  the  middle  of  the  last  century,  Lehman,  a  German  miner, 
proposed  to  divide  rocks  into  three  classes,  the  first  and  oldest  to  be 
called  primitive,  comprising  the  hypogene,  or  plutonic  and  metamor- 
phic  rocks;  the  next  to  be  termed  secondary,  comprehending  the 
aqueous  or  fossiliferous  strata;  and  the  remainder,  or  third  class, 
corresponding  to  our  alluvium,  ancient  and  modern,  which  he  referred 
to  "  local  floods,  and  the  deluge  of  Noah."  In  the  primitive  class,  he 
said,  such  as  granite  and  gneiss,  there  are  no  organic  remains,  nor 
any  signs  of  materials  derived  from  the  ruins  of  pre-existing  rocks. 
Their  origin,  therefore,  may  have  been  purely  chemical,  antecedent 
to  the  creation  of  living  beings,  and  probably  coeval  with  the  birth  of 
the  world  itself.  The  secondary  formations,  on  the  contrary,  which 
often  contain  sand,  pebbles,  and  organic  remains,  must  have  been 
mechanical  deposits,  produced  after  the  planet  had  become  the  habi- 
tation of  animals  and  plants.  This  bold  generalization,  although  an- 
ticipated in  some  measure  by  Steno,  a  century  before,  in  Italy, 
formed  at  the  time  an  important  step  in  the  progress  of  geology,  and 
sketched  out  correctly  some  of  the  leading  divisions  into  which  rocks 
may  be  separated.  About  half  a  century  later,  Werner,  so  justly 
celebrated  for  his  improved  methods  of  discriminating  the  mineralo- 
gical  characters  of  rocks,  attempted  to  improve  Lehman's  classification, 
and  with  this  view  intercalated  a  class,  called  by  him  "  the  transition 
formations,"  between  the  primitive  and  secondary.  Between  these 
last  he  had  discovered,  in  northern  Germany,  a  series  of  strata, 
which  in  their  mineral  peculiarities  were  of  an  intermediate  character, 
partaking  in  some  degree  of  the  crystalline  nature  of  micaceous  schist 
and  clay-slate,  and  yet  exhibiting  here  and  there  signs  of  a  mechani- 
cal origin  and  organic  remains.  For  this  group,  therefore,  forming  a 
passage  between  Lehman's  primitive  and  secondary  rocks,  the  name 
of  ilbergang  or  transition  was  proposed.  They  consisted  principally 
of  clay-slate  and  an  argillaceous  sandstone,  called  grauwacke,  and 
partly  of  calcareous  beds.  It  happened  in  the  district  which  Werner 
first  investigated,  that  both  the  primitive  and  transition  strata  were 
highly  inclined,  while  the  beds  of  the  newer  fossiliferous  rocks,  the 
secondary  of  Lehman,  were  horizontal.  To  these  latter,  therefore, 
he  gave  the  name  offlotz,  or  "  a  level  floor;"  and  every  deposit  more 
modern  than  the  chalk,  which  was  classed  as  the  uppermost  of  the 
flbtz  series,  was  designated  "  the  overflowed  land,"  an  expression  which 
may  be  regarded  as  equivalent  to  alluvium,  although  under  this  appel- 
lation were  confounded  all  the  strata  afterwards  called  tertiary,  of 
which  Werner  had  scarcely  any  'knowledge.  As  the  followers  of 
Werner  soon  discovered  that  the  inclined  position  of  the  "  transition 
beds,"  and  the  horizontality  of  the  flotz,  or  newer  fossiliferous  strata, 
were  mere  local  accidents,  they  soon  abandoned  the  term  flotz ;  and 


92  NEPTUNIAN   THEORY.  [Cu.  VIII. 

the  four  dirisions  of  the  Wernerian  school  were  then  named  primitive, 
transition,  secondary,  and  alluvial. 

As  to  the  trappean  rocks,  although  their  igneous  origin  had  been 
already  demonstrated  by  Arduino,  Fortis,  Faujas,  and  others,  and 
especially  by  Desmarest,  they  were  all  regarded  by  Werner  as  aqueous, 
and  as  mere  subordinate  members  of  the  secondary  series.* 

This  theory  of  Werner's  was  called  the  "  Neptunian,"  and  for  many 
years  enjoyed  much  popularity.  It  assumed  that  the  globe  had  been 
at  first  invested  by  an  universal  chaotic  ocean,  holding  the  materials 
of  all  rocks  in  solution.  From  the  waters  of  this  ocean,  granite, 
gneiss,  and  other  crystalline  formations,  were  first  precipitated ;  and 
afterwards,  when  the  waters  were  purged  of  these  ingredients,  and 
more  nearly  resembled  those  of  our  actual  seas,  the  transition  strata 
were  deposited.  These  were  of  a  mixed  character,  not  purely  che- 
mical, because  the  waves  and  currents  had  already  begun  to  wear 
down  solid  land,  and  to  give  rise  to  pebbles,  sand,  and  mud ;  nor  en- 
tirely without  fossils,  because  a  few  of  the  first  marine  animals  had 
begun  to  exist.  After  this  period,  the  secondary  formations  were 
accumulated  in  waters  resembling  those  of  the  present  ocean,  except 
at  certain  intervals,  when,  from  causes  wholly  unexplained,  a  partial 
recurrence  of  the  "  chaotic  fluid  "  took  place,  during  which  various 
trap  rocks,  some  highly  crystalline,  were  formed.  This  arbitrary 
hypothesis  rejected  all  intervention  of  igneous  agency,  volcanos  being 
regarded  as  modern,  partial,  and  superficial  accidents,  of  trifling 
account  among  the  great  causes  which  have  modified  the  external 
structure  of  the  globe. 

Meanwhile  Hutton,  a  contemporary  of  Werner,  began  to  teach,  in 
Scotland,  that  granite  as  well  as  trap  was  of  igneous  origin,  and  had 
at  various  periods  intruded  itself  in  a  fluid  state  into  different  parts  of 
the  earth's  crust.  He  recognized  and  faithfully  described  many  of  the 
phenomena  of  granitic  veins,  and  the  alterations  produced  by  them 
on  the  invaded  strata,  which  will  be  treated  of  in  the  thirty-third 
chapter.  He,  moreover,  advanced  the  opinion,  that  the  crystalline 
strata  called  primitive  had  not  been  precipitated  from  a  primaeval 
ocean,  but  were  sedimentary  strata  altered  by  heat.  In  his  writings, 
therefore,  and  in  those  of  his  illustrator,  Playfair,  we  find  the  germ 
of  that  metamorphic  theory  which  has  been  already  hinted  at  in  the 
first  chapter,  and  which  will  be  more  fully  expounded  in  the  thirty- 
fourth  and  thirty-fifth  chapters. 

At  length,  after  much  controversy,  the  doctrine  of  the  igneous 
origin  of  trap  and  granite  made  its  way  into  general  favour ;  but 
although  it  was,  in  consequence,  admitted  that  both  granite  and  trap 
had  been  produced  at  many  successive  periods,  the  term  primitive  or 
primary  still  continued  to  be  applied  to  the  crystalline  formations 
in  general,  whether  stratified,  like  gneiss,  or  unstratified,  like  granite. 
The  pupil  was  told  that  granite  was  a  primary  rock,  but  that  some 
granites  were  newer  than  certain  secondary  formations ;  and  in  con- 

*  See  Principles  of  Geology,  vol.  i.  chap.  iv. 


CH.  VIII.]  ON   THE   TEEM    "  TRANSITION."  93 

formity  with  the  spirit  of  the  ancient  language,  to  which  the  teacher 
was  still  determined  to  adhere,  a  desire  was  naturally  engendered  of 
extenuating  the  importance  of  those  more  modern  granites,  the  true 
dates  of  which  new  observations  were  continually  bringing  to  light. 

A  no  less  decided  inclination  was  shown  to  persist  in  the  use  of 
the  term  "transition,"  after  it  had  been  proved  to  be  almost  as 
faulty  in  its  original  application  as  that  of  flotz.  The  name  of 
transition,  as  already  stated,  was  first  given  by  Werner,  to  designate 
a  mineral  character,  intermediate  between  the  highly  crystalline  or 
metamorphic  state  and  that  of  an  ordinary  fossiliferous  rock.  But 
the  term  acquired  also  from  the  first  a  chronological  import,  because 
it  had  been  appropriated  to  sedimentary  formations,  which,  in  the 
Hartz  and  other  parts  of  Germany,  were  more  ancient  than  the 
oldest  of  the  secondary  series,  and  were  characterized  by  peculiar 
fossil  zoophytes  and  shells.  When,  therefore,  geologists  found  in 
other  districts  stratified  rocks  occupying  the  same  position,,  and 
inclosing  similar  fossils,  they  gave  to  them  also  the  name  of  tran- 
sition^ according  to  rules  which  will  be  explained  in  the  next 
chapter ;  yet,  in  many  cases,  such  rocks  were  found  not  to  exhibit 
the  same  mineral  texture  which  Werner  had  called  transition.  On 
the  contrary,  many  of  them  were  not  more  crystalline  than  different 
members  of  the  secondary  class ;  while,  on  the  other  hand,  these 
last  were  sometimes  found  to  assume  a  semi-crystalline  and  almost 
metamorphic  aspect,  and  thus,  on  lithological  grounds,  to  deserve 
equally  the  name  of  transition.  So  remarkably  was  this  the  case  in  ' 
the  Swiss  Alps,  that  certain  rocks,  which  had  for  years  been  regarded 
by  some  of  the  most  skilful  disciples  of  Werner  to  be  transition,  were 
at  last  acknowledged,  when  their  relative  position  and  fossils  were 
better  understood,  to  belong  to  the  newest  of  the  secondary  groups  ; 
nay,  some  of  them  have  actually  been  discovered  to  be  members  of 
the  lower  tertiary  series  !  If,  under  such  circumstances,  the  name  of 
transition  was  retained,  it  is  clear  that  it  ought  to  have  been  applied 
without  reference  to  the  age  of  strata,  and  simply  as  expressive  of  a 
mineral  peculiarity.  The  continued  appropriation  of  the  term  to 
formations  of  a  given  date,  induced  geologists  to  go  on  believino-  that 
the  ancient  strata  so  designated  bore  a  less  resemblance  to  the 
secondary  than  is  really  the  case,  and  to  imagine  that  these  last  never 
pass,  as  they  frequently  do,  into  metamorphic  rocks. 

The  poet  Waller,  when  lamenting  over  the  antiquated  style  of 
Chaucer,  complains  that  — 

We  write  in  sand,  our  language  grows, 
And,  like  the  tide,  our  work  o'erflows. 

But  the  reverse  is  true  in  geology ;  for  here  it  is  our  work  which 
continually  outgrows  the  language.  The  tide  of  observation  advances 
with  such  speed  that  improvements  in  theory  outrun  the  changes  of 
nomenclature ;  and  the  attempt  to  inculcate  new  truths  by  words 
invented  to  express  a  different  or  opposite  opinion,  tends  constantly, 


94  CHRONOLOGICAL   ARRANGEMENT  [Cn.  VIII. 

by  the  force  of  association,  to  perpetuate  error ;  so  that  dogmas 
renounced  by  the  reason  still  retain  a  strong  hold  upon  the  imagi- 
nation. 

In  order  to  reconcile  the  old  chronological  views  with  the  new 
doctrine  of  the  igneous  origin  of  granite,  the  following  hypothesis 
was  substituted  for  that  of  the  Neptunists.  Instead  of  beginning 
with  an  aqueous  menstruum  or  chaotic  fluid,  the  materials  of  the 
present  crust  of  the  earth  were  supposed  to  have  been  at  first  in  a 
state  of  igneous  fusion,  until  part  of  the  heat  having  been  diffused 
into  surrounding  space,  the  surface  of  the  fluid  consolidated,  and 
formed  a  crust  of  granite.  This  covering  of  crystalline  stone,  which 
afterwards  grew  thicker  and  thicker  as  it  cooled,  was  so  hot,  at  first, 
that  no  water  could  exist  upon  it ;  but  -  as  the  refrigeration  pro- 
ceeded, the  aqueous  vapour  in  the  atmosphere  was  condensed,  and, 
falling  in  rain,  gave  rise  to  the  first  thermal  ocean.  So  high  was  the 
temperature  of  this  boiling  sea,  that  no  aquatic  beings  could  inhabit 
its  waters,  and  its  deposits  were  not  only  devoid  of  fossils,  but,  like 
those  of  some  hot  springs,  were  highly  crystalline.  Hence  the 
origin  of  the  primary  or  crystalline  strata,  —  gneiss,  mica-schist,  and 
the  rest. 

Afterwards,  when  the  granitic  crust  had  been  partially  broken  up, 
land  and  mountains  began  to  rise  above  the  waters,  and  rains  and 
torrents  to  grind  down  rock,  so  that  sediment  was  spread  over  the 
bottom  of  the  seas.  Yet  the  heat  still  remaining  in  the  solid 
supporting  substances  was  sufficient  to  increase  the  chemical  action 
exerted  by  the  water,  although  not  so  intense  as  to  prevent  the  intro- 
duction and  increase  of  some  living  beings.  During  this  state  of 
things  some  of  the  residuary  mineral  ingredients  of  the  primaeval 
ocean  were  precipitated,  and  formed  deposits  (the  transition  strata 
of  Werner),  half  chemical  and  half  mechanical,  and  containing  a  few 
fossils. 

By  this  new  theory,  which  was  in  part  a  revival  of  the  doctrine  of 
Leibnitz,  published  in  1680,  on  the  igneous  origin  of  the  planet,  the 
old  ideas  respecting  the  priority  of  all  crystalline  rocks  to  the  creation 
of  organic  beings,  were  still  preserved ;  and  the  mistaken  notion  that 
all  the  semi-crystalline  and  partially  fossiliferous  rocks  belonged  to 
one  period,  while  all  the  earthy  and  uncrystalline  formations  origin- 
ated at  a  subsequent  epoch,  was  also  perpetuated. 

It  may  or  may  not  be  true,  as  the  great  Leibnitz  imagined,  that 
the  whole  planet  was  once  in  a  state  of  liquefaction  by  heat ;  but 
there  are  certainly  no  geological  proofs  that  the  granite  which  con- 
stitutes the  foundation  of  so  much  of  the  earth's  crust  was  ever  at  once 
in  a  state  of  universal  fusion.  On  the  contrary,  all  our  evidence 
tends  to  show  that  the  formation  of  granite,  like  the  deposition  of 
the  stratified  rocks,  has  been  successive,  and  that  different  portions  of 
granite  have  been  in  a  melted  state  at  distinct  and  often  distant 
periods.  One  mass  was  solid,  and  had  been  fractured,  before  another 
body  of  granitic  matter  was  injected  into  it,  or  through  it,  in  the  form 
of  veins.  Some  granites  are  more  ancient  than  any  known  fossiliferous 


Cn.  VIII.]  OF   HOCKS   IN   GENERAL.  95 

rocks ;  others  are  of  secondary ;  and  some,  such  as  that  of  Mont 
Blanc  and  part  of  the  central  axis  of  the  Alps,  of  tertiary  origin.  In 
short,  the  universal  fluidity  of  the  crystalline  foundations  of  the 
earth's  crust,  can  only  be  understood  in  the  same  sense  as  the  uni- 
versality of  the  ancient  ocean.  All  the  land  has  been  under  water, 
but  not  all  at  one  time  ;  so  all  the  subterranean  unstratified  rocks  to 
which  man  can  obtain  access  have  been  melted,  but  not  simulta- 
neously. 

In  the  present  work  the  four  great  classes  of  rocks,  the  aqueous, 
plutonic,  volcanic,  and  metamorphic,  will  form  four  parallel,  or 
nearly  parallel,  columns  in  one  chronological  table.  They  will  be 
considered  as  four  sets  of  monuments  relating  to  four  contempo- 
raneous, or  nearly  contemporaneous,  series  of  events.  I  shall  en- 
deavour, in  a  subsequent  chapter  on  the  plutonic  rocks,  to  explain 
the  manner  in  which  certain  masses  belonging  to  each  of  the  four 
classes  of  rocks  may  have  originated  simultaneously  at  every  geolo- 
gical period,  and  how  the  earth's  crust  may  have  been  continually 
remodelled,  above  and  below,  by  aqueous  and  igneous  causes,  from 
times  indefinitely  remote.  In  the  same  manner  as  aqueous  and 
fossiliferous  strata  are  now  formed  in  certain  seas  or  lakes,  while  in 
other  places  volcanic  rocks  break  out  at  the  surface,  and  are  con- 
nected with  reservoirs  of  melted  matter  at  vast  depths  in  the  bowels 
of  the  earth,  —  so,  at  every  era  of  the  past,  fossiliferous  deposits  and 
superficial  igneous  rocks  were  in  progress  contemporaneously  with 
others  of  subterranean  and  plutonic  origin,  and  some  sedimentary 
strata  were  exposed  to  heat,  and  made  to  assume  a  crystalline  or 
metamorphic  structure. 

It  can  by  no  means  be  taken  for  granted,  that  during  all  these 
changes  the  solid  crust  of  the  earth  has  been  increasing  in  thickness. 
It  has  been  shown,  that  so  far  as  aqueous  action  is  concerned,  the 
gain  by  fresh  deposits,  and  the  loss  by  denudation,  must  at  each 
period  have  been  equal  (see  above,  p.  68.) ;  and  in  like  manner,  in 
the  inferior  portion  of  the  earth's  crust,  the  acquisition  of  new  crys- 
talline rocks,  at  each  successive  era,  may  merely  have  counter- 
balanced the  loss  sustained  by  the  melting  of  materials  previously 
consolidated.  As  to  the  relative  antiquity  of  the  crystalline  found- 
ations of  the  earth's  crust,  when  compared  to  the  fossiliferous  and 
volcanic  rocks  which  they  support,  I  have  already  stated,  in  the  first 
chapter,  that  to  pronounce  an  opinion  on  this  matter  is  as  difficult  as 
at  once  to  decide  which  of  the  two,  whether  the  foundations  or  super- 
structure of  an  ancient  city  built  on  wooden  piles,  may  be  the  oldest. 
We  have  seen  that,  to  answer  this  question,  we  must  first  be  prepared 
to  say  whether  the  work  of  decay  and  restoration  had  gone  on  most 
rapidly  above  or  below ;  whether  the  average  duration  of  the  piles  has 
exceeded  that  of  the  stone  buildings,  or  the  contrary.  So  also  in 
regard  to  the  relative  age  of  the  superior  and  inferior  portions  of  the 
earth's  crust;  we  cannot  hazard  even  a  conjecture  on  this  point, 
until  we  know  whether,  upon  an  average,  the  power  of  water  above, 
or  that  of  heat  below,  is  most  efficacious  in  giving  new  forms  to  solid 
matter. 


96  CHRONOLOGICAL   ARRANGEMENT    OF   ROCKS.     [Cn.  VIII. 

After  the  observations  which  have  now  been  made,  the  reader  will 
perceive  that  the  term  primary  must  either  be  entirely  renounced,  or, 
if  retained,  must  be  differently  defined,  and  not  made  to  designate  a 
set  of  crystalline  rocks,  some  of  which  are  already  ascertained  to  be 
newer  than  all  the  secondary  formations.  In  this  work  I  shall  follow 
most  nearly  the  method  proposed  by  Mr.  Boue,  who  has  called  all 
fossiliferous  rocks  older  than  the  secondary  by  the  name  of  primary. 
To  prevent  confusion,  I  shall  sometimes  speak  of  these  last  as  the 
primary  fossiliferous  formations ;  because  the  word  primary  has 
hitherto  been  most  generally  connected  with  the  idea  of  a  non- 
fossiliferous  rock.  Some  geologists,  to  avoid  misapprehension,  have 
introduced  the  term  Paleozoic  for  primary,  from  TroXatov,  "  ancient," 
and  £wov,  "  an  organic  being,"  still  retaining  the  terms  secondary  and 
tertiary;  Mr.  Phillips,  for  the  sake  of  uniformity,  has  proposed 
Mesozoic,  for  secondary,  from  /xeo-oc,  "  middle,"  &c. ;  and  Cainozoic,  for 
tertiary,  from  /ccuvoe,  "  recent,"  &c. ;  but  the  terms  primary,  secondary, 
and  tertiary  are  synonymous,  and  have  the  claim  of  priority  in 
their  favour. 

If  we  can  prove  any  plutonic,  volcanic,  or  metamorphic  rocks  to  be 
older  than  the  secondary  formations,  such  rocks  will  also  be  primary, 
according  to  this  system.  Mr.  Boue  having  with  propriety  ex- 
cluded the  metamorphic  rocks,  as  a  class,  from  the  primary  form- 
ations, proposed  to  call  them  all  "  crystalline  schists." 

As  there  are  secondary  fossiliferous  strata,  so  we  shall  find  that 
there  are  plutonic,  volcanic,  and  metamorphic  rocks  of  contempora- 
neous origin,  which  I  shall  also  term  secondary. 

In  the  next  chapter  it  will  be  shown  that  the  strata  above  the 
chalk  have  been  called  tertiary.  If,  therefore,  we  discover  any  vol- 
canic, plutonic,  or  metamorphic  rocks,  which  have  originated  since 
the  deposition  of  the  chalk,  these  also  will  rank  as  tertiary  form- 
ations. 

It  may  perhaps  be  suggested  that  some  metamorphic  strata,  and 
some  granites,  may  be  anterior  in  date  to  the  oldest  of  the  primary 
fossiliferous  rocks.  This  opinion  is  doubtless  true,  and  will  be  dis- 
cussed in  future  chapters ;  but  I  may  here  observe,  that  when  we 
arrange  the  four  classes  of  rocks  in  four  parallel  columns  in  one  table 
of  chronology,  it  is  by  no  means  assumed  that  these  columns  are  all 
of  equal  length  ;  one  may  begin  at  an  earlier  period  than  the  rest,  and 
another  may  come  down  to  a  later  point  of  time.  In  the  small  part 
of  the  globe  hitherto  examined,  it  is  hardly  to  be  expected  that  we 
should  have  discovered  either  the  oldest  or  the  newest  members  of 
each  of  the  four  classes  of  rocks.  Thus,  if  there  be  primary,  second- 
ary, and  tertiary  rocks  of  the  aqueous  or  fossiliferous  class,  and  in 
like  manner  primary,  secondary,  and  tertiary  hypogene  formations, 
we  may  not  be  yet  acquainted  with  the  most  ancient  of  the  primary 
fossiliferous  beds,  or  with  the  newest  of  the  hypogene. 


CH.  IX.]  DIFFERENT  AGES   OF   AQUEOUS  ROCKS.  97 


CHAPTER  IX. 

ON  THE  DIFFERENT  AGES  OF  THE  AQUEOUS  ROCKS. 

On  the  three  principal  tests  of  relative  age  —  superposition,  mineral  character,  and 
fossils— Change  of  mineral  character  and  fossils  in  the  same  continuous  forma- 
tion— Proofs  that  distinct  species  of  animals  and  plants  have  lived  at  successive 
periods — Distinct  provinces  of  indigenous  species  — Great  extent  of  single  pro- 
vinces—Similar laws  prevailed  at  successive  geological  periods  — Eelative 
importance  of  mineral  and  palseontological  characters—  Test  of  age  by  included 
fragments — Frequent  absence  of  strata  of  intervening  periods — Principal  groups 
of  strata  in  western  Europe. 

IN  the  last  chapter  I  spoke  generally  of  the  chronological  relations  of 
the  four  great  classes  of  rocks,  and  I  shall  now  treat  of  the  aqueous 
rocks  in  particular,  or  of  the  successive  periods  at  which  the  different 
fossiliferous  formations  have  been  deposited. 

There  are  three  principal  tests  by  which  we  determine  the  age  of 
a  given  set  of  strata;  first,  superposition;  secondly,  mineral  cha- 
racter ;  and,  thirdly,  organic  remains.  Some  aid  can  occasionally  be 
derived  from  a  fourth  kind  of  proof,  namely,  the  fact  of  one  deposit 
including  in  it  fragments  of  a  pre-existing  rock,  by  which  the  rela- 
tive ages  of  the  two  may,  even  in  the  absence  of  all  other  evidence, 
be  determined. 

Superposition.  —  The  first  and  principal  test  of  the  age  of  one 
aqueous  deposit,  as  compared  to  another,  is  relative  position.  It  has 
been  already  stated,  that,  where  strata  are  horizontal,  the  bed  which 
lies  uppermost  is  the  newest  of  the  whole,  and  that  which  lies  at  the 
bottom  the  most  ancient.  So,  of  a  series  of  sedimentary  formations, 
they  are  like  volumes  of  history,  in  which  each  writer  has  recorded 
the  annals  of  his  own  times,  and  then  laid  down  the  book,  with  the 
last  written  page  uppermost,  upon  the  volume  in  which  the  events  of 
the  era  immediately  preceding  were  commemorated.  In  this  manner 
a  lofty  pile  of  chronicles  is  at  length  accumulated ;  and  they  are  so 
arranged  as  to  indicate,  by  their  position  alone,  the  order  in  which 
the  events  recorded  in  them  have  occurred. 

In  regard  to  the  crust  of  the  earth,  however,  there  are  some  re- 
gions where,  as  the  student  has  already  been  informed,  the  beds  have 
been  disturbed,  and  sometimes  extensively  thrown  over  and  turned 
upside  down.  (See  pp.  58,  59.)  But  an  experienced  geologist  can 
rarely  be  deceived  by  these  exceptional  cases.  When  he  finds  that 
the  strata  are  fractured,  curved,  inclined,  or  vertical,  he  knows  that 
the  original  order  of  superposition  must  be  doubtful,  and  he  then 
endeavours  to  find  sections  in  some  neighbouring  district  where  the 
strata  are  horizontal,  or  only  slightly  inclined.  Here,  the  true  order 
of  sequence  of  the  entire  series  of  deposits  being  ascertained,  a  key  is 

H 


98  TESTS   OF   THE   DIFFERENT   AGES  [Cn.  IX, 

furnished  for  settling  the  chronology  of  those  strata  where  the  dis- 
placement is  extreme. 

Mineral  character.  —  The  same  rocks  may  often  be  observed  to 
retain  for  miles,  or  even  hundreds  of  miles,  the  same  mineral  pecu- 
liarities, if  we  follow  the  planes  of  stratification,  or  trace  the  beds,  if 
they  be  undisturbed,  in  a  horizontal  direction.  But  if  we  pursue 
them  vertically,  or  in  any  direction  transverse  to  the  planes  of  strati- 
fication, this  uniformity  ceases  almost  immediately.  In  that  case  we 
can  scarcely  ever  penetrate  a  stratified  mass  for  a  few  hundred  yards 
without  beholding  a  succession  of  extremely  dissimilar  rocks,  some  of 
fine,  others  of  coarse  grain,  some  of  mechanical,  others  of  chemical 
origin ;  some  calcareous,  others  argillaceous,  and  others  siliceous. 
These  phenomena  lead  to  the  conclusion,  that  rivers  and  currents 
have  dispersed  the  same  sediment  over  wide  areas  at  one  period,  but 
at  successive  periods  have  been  charged,  in  the  same  region,  with 
very  different  kinds  of  matter.  The  first  observers  were  so  astonished 
at  the  vast  spaces  over  which  they  were  able  to  follow  the  same  homo- 
geneous rocks  in  a  horizontal  direction,  that  they  came  hastily  to  the 
opinion,  that  the  whole  globe  had  been  environed  by  a  succession  of 
distinct  aqueous  formations,  disposed  round  the  nucleus  of  the  planet, 
like  the  concentric  coats  of  an  onion.  But  although,  in  fact,  some 
formations  may  be  continuous  over  districts  as  large  as  half  of  Europe, 
or  even  more,  yet  most  of  them  either  terminate  wholly  within  narrower 
limits,  or  soon  change  their  lithological  character.  Sometimes  they 
thin  out  gradually,  as  if  the  supply  of  sediment  had  failed  in  that 
direction,  or  they  come  abruptly  to  an  end,  as  if  we  had  arrived  at  the 
borders  of  the  ancient  sea  or  lake  which  served  as  their  receptacle. 
It  no  less  frequently  happens  that  they  vary  in  mineral  aspect  and 
composition,  as  we  pursue  them  horizontally.  For  example,  we  trace 
a  limestone  for  a  hundred  miles,  until  it  becomes  more  arenaceous, 
and  finally  passes  into  sand,  or  sandstone.  We  may  then  follow  this 
sandstone,  already  proved  by  its  continuity  to  be  of  the  same  age, 
throughout  another  district  a  hundred  miles  or  more  in  length. 

Organic  remains.  —  This  character  must  be  used  as  a  criterion  of 
the  age  of  a  formation  or  of  the  contemporaneous  origin  of  two 
deposits  in  distant  places,  under  very  much  the  same  restrictions  as 
the  test  of  mineral  composition. 

First,  the  same  fossils  may  be  traced  over  wide  regions,  if  we 
examine  strata  in  the  direction  of  their  planes,  although  by  no  means 
for  indefinite  distances. 

Secondly,  while  the  same  fossils  prevail  in  a  particular  set  of 
strata  for  hundreds  of  miles  in  a  horizontal  direction,  we  seldom  meet 
with  the  same  remains  for  many  fathoms,  and  very  rarely  for  several 
hundred  yards,  in  a  vertical  line,  or  a  line  transverse  to  the  strata. 
This  fact  has  now  been  verified  in  almost  all  parts  of  the  globe,  and 
has  led  to  a  conviction,  that  at  successive  periods  of  the  past,  the 
same  area  of  land  and  water  has  been  inhabited  by  species  of  animals 
and  plants  even  more  distinct  than  those  which  now  people  the  anti- 
podes, or  which  now  co-exist  in  the  arctic,  temperate,  and  tropical 


CH.  IX.]  OF   AQUEOUS  ROCKS.  99 

zones.  It  appears,  that  from  the  remotest  periods  there  has  been 
ever  a  coming  in  of  new  organic  forms,  and  an  extinction  of  those 
which  pre-existed  on  the  earth ;  some  species  having  endured  for  a 
longer,  others  for  a  shorter,  time  ;  while  none  have  ever  re-appeared 
after  once  dying  out.  The  law  which  has  governed  the  creation  and 
extinction  of  species  seems  to  be  expressed  in  the  verse  of  the 
poet,— . 

Natura  il  fece,  e  poi  ruppe  la  stampa.        ARIOSTO. 

Nature  made  him,  and  then  broke  the  die. 

And  this  circumstance  it  is,  which  confers  on  fossils  their  highest 
value  as  chronological  tests,  giving  to  each  of  them,  in  the  eyes  of 
the  geologist,  that  authority  which  belongs  to  contemporary  medals 
in  history. 

The  same  cannot  be  said  of  each  peculiar  variety  of  rock;  for 
some  of  these,  as  red  marl  and  red  sandstone,  for  example,  may 
occur  at  once  at  the  top,  bottom,  and  middle  of  the  entire  sedi- 
mentary series ;  exhibiting  in  each  position  so  perfect  an  identity  of 
mineral  aspect  as  to  be  undistinguishable.  Such  exact  repetitions, 
however,  of  the  same  mixtures  of  sediment  have  not  often  been  pro- 
duced, at  distant  periods,  in  precisely  the  same  parts  of  the  globe ; 
and,  even  where  this  has  happened,  we  are  seldom  in  any  danger  of 
confounding  together  the  monuments  of  remote  eras,  when  we  have 
studied  their  imbedded  fossils  and  their  relative  position. 

It  was  remarked  that  the  same  species  of  organic  remains  cannot 
be  traced  horizontally,  or  in  the  direction  of  the  planes  of  strati- 
fication for  indefinite  distances.  This  might  have  been  expected 
from  analogy ;  for  when  we  inquire  into  the  present  distribution  of 
living  beings  we  find  that  the  habitable  surface  of  the  sea  and  land 
may  be  divided  into  a  considerable  number  of  distinct  provinces, 
each  peopled  by  a  peculiar  assemblage  of  animals  and  plants.  In  the 
Principles  of  Geology,  I  have  endeavoured  to  point  out  the  extent 
and  probable  origin  of  these  separate  divisions ;  and  it  was  shown 
that  climate  is  only  one  of  many  causes  on  which  they  depend,  and 
that  difference  of  longitude  as  well  as  latitude  is  generally  accom- 
panied by  a  dissimilarity  of  indigenous  species. 

As  different  seas,  therefore,  and  lakes  are  inhabited,  at  the  same 
period,  by  different  aquatic  animals  and  plants,  and  as  the  lands  ad- 
joining these  may  be  peopled  by  distinct  terrestrial  species,  it  follows 
that  distinct  fossils  will  be  imbedded  in  contemporaneous  deposits. 
If  it  were  otherwise — if  the  same  species  abounded  in  every  climate, 
or  in  every  part  of  the  globe  where,  so  far  as  we  can  discover,  a 
corresponding  temperature  and  other  conditions  favourable  to  their 
existence  are  found  —  the  identification  of  mineral  masses  of  the 
same  age,  by  means  of  their  included  organic  contents,  would  be  a 
matter  of  still  greater  certainty. 

Nevertheless,  the  extent  of  some  single  zoological  provinces,  espe- 
cially those  of  marine  animals,  is  very  great ;  and  our  geological 
researches  have  proved  that  the  same  laws  prevailed  at  remote 

H   2 


100  TESTS   OF    THE   DIFFERENT   AGES  [Ca.  IX. 

periods ;  for  the  fossils  are  often  identical  throughout  wide  spaces,  and 
in  detached  deposits,  consisting  of  rocks  varying  entirely  in  their 
mineral  nature. 

The  doctrine  here  laid  down  will  be  more  readily  understood,  if  we 
reflect  on  what  is  now  going  on  in  the  Mediterranean.  That  entire 
sea  may  be  considered  as  one  zoological  province ;  for  although  certain 
species  of  testacea  and  zoophytes  may  be  very  local,  and  each  region 
has  probably  some  species  peculiar  to  it,  still  a  considerable  number 
are  common  to  the  whole  Mediterranean.  If,  therefore,  at  some 
future  period,  the  bed  of  this  inland  sea  should  be  converted  into  land, 
the  geologist  might  be  enabled,  by  reference  to  organic  remains,  to 
prove  the  contemporaneous  origin  of  various  mineral  masses  scattered 
over  a  space  equal  in  area  to  half  of  Europe. 

Deposits,  for  example,  are  well  known  to  be  now  in  progress  in  this 
sea  in  the  deltas  of  the  Po,  Rhone,  Nile,  and  other  rivers,  which  differ 
as  greatly  from  each  other  in  the  nature  of  their  sediment  as  does  the 
composition  of  the  mountains  which  they  drain.  There  are  also  other 
quarters  of  the  Mediterranean,  as  off  the  coast  of  Campania,  or  near 
the  base  of  Etna,  in  Sicily,  or  in  the  Grecian  Archipelago,  where 
another  class  of  rocks  is  now  forming ;  where  showers  of  volcanic 
ashes  occasionally  fall  into  the  sea,  and  streams  of  lava  overflow  its 
bottom  ;  and  where,  in  the  intervals  between  volcanic  eruptions,  beds 
of  sand  and  clay  are  frequently  derived  from  the  waste  of  cliffs,  or 
the  turbid  waters  of  rivers.  Limestones,  moreover,  such  as  the  Italian 
travertins,  are  here  and  there  precipitated  from  the  waters  of  mineral 
springs,  some  of  which  rise  up  from  the  bottom  of  the  sea.  In  all 
these  detached  formations,  so  diversified  in  their  lithological  cha- 
racters, the  remains  of  the  same  shells,  corals,  Crustacea,  and  fish  are 
becoming  inclosed ;  or,  at  least,  a  sufficient  number  must  be  common 
to  the  different  localities  to  enable  the  zoologist  to  refer  them  all  to 
one  contemporaneous  assemblage  of  species. 

There  are,  however,  certain  combinations  of  geographical  circum- 
stances which  cause  distinct  provinces  of  animals  and  plants  to  be 
separated  from  each  other  by  very  narrow  limits ;  and  hence  it  must 
happen,  that  strata  will  be  sometimes  formed  in  contiguous  regions, 
differing  widely  both  in  mineral  contents  and  organic  remains.  Thus, 
for  example,  the  testacea,  zoophytes,  and  fish  of  the  Red  Sea  are,  as 
a  group,  extremely  distinct  from  those  inhabiting  the  adjoining  parts 
of  the  Mediterranean,  although  the  two  seas  are  separated  only  by 
the  narrow  isthmus  of  Suez.  Of  -the  bivalve  shells,  according  to 
Philippi,  not  more  than  a  fifth  are  common  to  the  Red  Sea  and  the 
sea  around  Sicily,  while  the  proportion  of  univalves  (or  Gasteropoda) 
is  still  smaller,  not  exceeding  eighteen  in  a  hundred.  Calcareous 
formations  have  accumulated  on  a  great  scale  in  the  Red  Sea  in 
modern  times,  and  fossil  shells  of  existing  species  are  well  preserved 
therein ;  and  we  know  that  at  the  mouth  of  the  Nile  large  deposits 
of  mud  are  amassed,  including  the  remains  of  Mediterranean  species. 
It  follows,  therefore,  that  if  at  some  future  period  the  bed  of  the 
Red  Sea  should  be  laid  dry,  the  geologist  might  experience  great 


CH.  IX.]  OF   AQUEOUS  ROCKS.  101 

difficulties  in  endeavouring  to  ascertain  the  relative  age  of  these 
formations,  which,  although  dissimilar  both  in  organic  and  mineral 
characters,  were  of  synchronous  origin. 

But,  on  the  otljer  hand,  we  must  not  forget  that  the  north-western 
shores  of  the  Arabian  Gulf,  the  plains  of  Egypt,  and  the  isthmus  of 
Suez  are  all  parts  of  one  province  of  terrestrial  species.  Small 
streams,  therefore,  occasional  land- floods,  and  those  winds  which  drift 
clouds  of  sand  along  the  deserts  might  carry  down  into  the  Red  Sea 
the  same  shells  of  fluviatile  and  land  testacea  which  the  Nile  is 
sweeping  into  its  delta,  together  with  some  remains  of  terrestrial 
plants  and  the  bones  of  quadrupeds,  whereby  the  groups  of  strata, 
before  alluded  to,  might,  notwithstanding  the  discrepancy  of  their 
mineral  composition  and  marine  organic  fossils,  be  shown  to  have 
belonged  to  the  same  epoch. 

Yet  while  rivers  may  thus  carry  down  the  same  fluviatile  and 
terrestrial  spoils  into  two  or  more  seas  inhabited  by  different  marine 
species,  it  will  much  more  frequently  happen,  that  the  co-existence 
of  terrestrial  species  of  distinct  zoological  and  botanical  provinces 
will  be  proved  by  the  identity  of  the  marine  beings  which  inhabited 
the  intervening  space.  Thus,  for  example,  the  land  quadrupeds  and 
shells  of  the  south  of  Europe,  north  of  Africa,  and  north-west  of 
Asia  differ  considerably,  yet  their  remains  are  all  washed  down  by 
rivers  flowing  from  these  three  countries  into  the  Mediterranean. 

In  some  parts  of  the  globe,  at  the  present  period,  the  line  of 
Demarcation  between  distinct  provinces  of  animals  and  plants  is  not 
very  strongly  marked,  especially  where  the  change  is  determined  by 
temperature,  as  it  is  in  seas  extending  from  the  temperate  to  the  tropical 
zone,  or  from  the  temperate  to  the  arctic  regions.  Here  a  gradual 
passage  takes  place  from  one  set  of  species  to  another.  In  like 
manner  the  geologist,  in  studying  particular  formations  of  remote 
periods,  has  sometimes  been  able  to  trace  the  gradation  from  one 
ancient  province  to  another,  by  observing  carefully  the  fossils  of  all 
the  intermediate  places.  His  success  in  thus  acquiring  a  knowledge 
of  the  zoological  or  botanical  geography  of  very  distant  eras  has  been 
mainly  owing  to  this  circumstance,  that  the  mineral  character  has  no 
tendency  to  be  affected  by  climate.  A  large  river  may  convey 
yellow  or  red  mud  into  some  part  of  the  ocean,  where  it  may  be 
dispersed  by  a  current  over  an  area  several  hundred  leagues  in 
length,  so  as  to  pass  from  the  tropics  into  the  temperate  zone.  If 
the  bottom  of  the  sea  be  afterwards  upraised,  the  organic  remains 
imbedded  in  such  yellow  or  red  strata  may  indicate  the  different 
animals  or  plants  which  once  inhabited  at  the  same  time  the  tem- 
perate and  equatorial  regions. 

It  may  be  true,  as  a  general  rule,  that  groups  of  the  same  species 
of  animals  and  plants  may  extend  over  wider  areas  than  deposits  of 
homogeneous  composition ;  and  if  so,  palseontological  characters  will 
be  of  more  importance  in  geological  classification  than  the  test  of 
mineral  composition ;  but  it  is  idle  to  discuss  the  relative  value  of 
these  tests,  as  the  aid  of  both  is  indispensable,  and  it  fortunately 

H   3 


102  CHRONOLOGICAL  ARRANGEMENT.      [Cn.  IX. 

happens,  that  where  the  one  criterion  fails,  we  can  often  avail  our- 
selves of  the  other. 

Test  by  included  fragments  of  older  rocks. — It  was  stated,  that 
independent  proof  may  sometimes  be  obtained  of  the  relative  date  of 
two  formations,  by  fragments  of  an  older  rock  being  included  in  a 
newer  one.  This  evidence  may  sometimes  be  of  great  use,  where  a 
geologist  is  at  a  loss  to  determine  the  relative  age  of  two  formations 
from  want  of  clear  sections  exhibiting  their  true  order  of  position,  or 
because  the  strata  of  each  group  are  vertical.  In  such  cases  we 
sometimes  discover  that  the  more  modern  rock  has  been  in  part 
derived  from  the  degradation  of  the  older.  Thus,  for  example,  we 
may  find  chalk  with  flints  in  one  part  of  a  country ;  and,  in  another, 
a  distinct  formation,  consisting  of  alternations  of  clay,  sand,  and 
pebbles.  If  some  of  these  pebbles  consist  of  similar  flint,  including 
fossil  shells,  sponges,  and  foraminifera,  of  the  same  species  as  those 
in  the  chalk,  we  may  confidently  infer  that  the  chalk  is  the  oldest  of 
the  two  formations. 

Chronological  groups. —  The  number  of  groups  into  which  the 
fossiliferous  strata  may  be  separated  are  more  or  less  numerous, 
according  to  the  views  of  classification  which  different  geologists 
entertain ;  but  when  we  have  adopted  a  certain  system  of  arrange- 
ment, we  immediately  find  that  a  few  only  of  the  entire  series  of 
groups  occur  one  upon  the  other  in  any  single  section  or  district. 
"  The  thinning  out  of  individual  strata  was  before  described  (p.  16.V 

Fig.  104. 


But  let  the  annexed  diagram  represent  seven  fossiliferous  groups, 
instead  of  as  many  strata.  It  will  then  be  seen  that  in  the  middle 
all  the  superimposed  formations  are  present ;  but  in  consequence  of 
some  of  them  thinning  out,  No.  2.  and  No.  5.  are  absent  at  one 
extremity  of  the  section,  and  No.  4.  at  the  other. 

In  another  diagram,  fig.  105.;  a  real  section  of  the  geological 
formations  in  the  neighbourhood  of  Bristol  and  the  Mendip  Hills  is 
presented  to  the  reader,  as  laid  down  on  a  true  scale  by  Professor 
Ramsay,  where  the  newer  groups  1,  2,  3,  4.  rest  unconformably  on 
the  formations  5  and  6.  Here  at  the  southern  end  of  the  line  of 
section  we  meet  with  the  beds  No.  3.  (the  New  Red  Sandstone)  resting 
immediately  on  No.  6.,  while  farther  north,  as  at  Dundry  Hill,  we 
behold  six  groups  superimposed  one  upon  the  other,  comprising  all 
the  strata  from  the  inferior  oolite  to  the  coal  and  carboniferous 
limestone.  The  limited  extension  of  the  groups  1  and  2.  is  owing 
to  denudation,  as  these  formations  end  abruptly,  and  have  left 
outlying  patches  to  attest  the  fact  of  their  having  originally  covered 
a  much  wider  area. 


OF   AQUEOUS  ROCKS. 


103 


Section  South  of  Bristol.  A.  C.  Ramsay., 

Length  of  section  4  miles.        a,  b.  Level  of  the  sea. 

1.  Inferior  oolite.  5.  Coal  measure. 

2.  Lias.  6.  Carboniferous  limestone. 

3.  New  red  sandstone.  7.  Old  red  sandstone. 

4.  Magnesian  conglomerate. 

In  many  instances,  however,  the  entire  absence  of  one  or  more 
formations  of  intervening  periods  between  two  groups,  such  as  3. 
and  5.  in  the  same  section,  arises,  not  from  the  destruction  of  what 
once  existed,  but  because  no  strata  of  an  intermediate* age  were  ever 
deposited  on  the  inferior  rock.  They  were  not  formed  at  that  place, 
either  because  the  region  was  dry  land  during  the  interval,  or  because 
it  was  part  of  a  sea  or  lake  to  which  no  sediment  was  carried. 

In  order,  therefore,  to  establish  a  chronological  succession  of 
fossiliferous  groups,  a  geologist  must  begin  with  a  single  section  in 
which  several  sets  of  strata  lie  one  upon  the  other.  He  must  then 
trace  these  formations,  by  attention  to  their  mineral  character  and 
fossils,  continuously,  as  far  as  possible,  from  the  starting  point.  As 
often  as  he  meets  with  new  groups,  he  must  ascertain  by  super- 
position their  age  relatively  to  those  first  examined,  and  thus  learn 
how  to  intercalate  them  in  a  tabular  arrangement  of  the  whole. 

By  this  means  the  German,  French,  and  English  geologists  have 
determined  the  succession  of  strata  throughout  a  great  part  of 
Europe,  and  have  adopted  pretty  generally  the  following  groups, 
almost  all  of  which  have  their  representatives  in  the  British  Islands. 

Groups  of  Fossiliferous  Strata  cbserved  in  Western  Europe,  ar- 
ranged in  what  is  termed  a  descending  Series,  or  beginning  with 
the  newest.  (See  a  more  detailed  Tabular  view,  pp.  104.  109.) 


1.  Post-Pliocene,  including  those  of  the 

Recent,  or  Human  period. 

2.  Newer  Pliocene,  or  Pleistocene. 

3.  Older  Pliocene. 

4.  Miocene. 

5.  Eocene. 

6.  Chalk. 

7.  Greensand  and  Wealden. 

8.  Upper  Oolite,  including  the  Purheck. 

9.  Middle  Oolite. 

10.  Lower  Oolite. 

11.  Lias. 

12.  Trias. 


Tertiary,     Supracretaceous  *,    or 
Cainozoic.f 


^Secondary,  or  Mesozoic. 


*  For  tertiary,  Sir  H.  De  La  Beche    are  superior  in  position  to  the  chalk, 
has  used  the  term  "  supracretaceous,"  a        f  For  an  explanation  of  Cainozoic 
name  implying  that  the  strata  so  called    &c.  see  above,  p.  95. 

H  4 


104     FOSSILIFEROUS   STRATA   OF   WESTERN   EUROPE.    [Cn.  IX. 


13.  Permian. 

14.  Coal. 

15.  Old  Red  sandstone,  or  Devonian. 

16.  Upper  Silurian. 

17.  Lower  Silurian. 

1 8.  Cambrian  and  older  fossiliferous  strata. 


( Primary  fossiliferous,    or    palaeo- 


zoic. 


It  is  not  pretended  that  the  three  principal  sections  in  the  above 
table,  called  primary,  secondary,  and  tertiary,  are  of  equivalent  im- 
portance, or  that  the  eighteen  subordinate  groups  comprise  monu- 
ments relating  to  equal  portions  of  past  time,  or  of  the  earth's  his- 
tory. But  we  can  assert  that  they  each  relate  to  successive  periods, 
during  which  certain  animals  and  plants,  for  the  most  part  peculiar 
to  their  respective  eras,  have  flourished,  and  during  which  different 
kinds  of  sediment  were  deposited  in  the  space  now  occupied  by 
Europe. 

If  we  were  disposed,  on  palaeontological  grounds  *,  to  divide  the 
entire  fossiliferous  series  into  a  few  groups  less  numerous  than  those 
in  the  above  table,  and  more  nearly  co-ordinate  in  value  than  the 
sections  called  primary,  secondary,  and  tertiary,  we  might,  perhaps, 
adopt  the  six  groups  or  periods  given  in  the  next  table. 

At  the  same  time,  I  may  observe,  that,  in  the  present  state  of  the 
science,  when  we  have  not  yet  compared  the  evidence  derivable  from 
all  classes  of  fossils,  not  even  those  most  generally  distributed,  such 
as  shells,  corals,  and  fish,  such  generalizations  are  premature,  and  can 
only  be  regarded  as  conjectural  or  provisional  schemes  for  the  found- 
ing of  large  natural  groups. 

Fossiliferous  Strata  of  Western  Europe  divided  into  Six   Groups. 

*'  P°5~PHocene       and  )  from  the  Post-Pliocene  to  the  Eocene  inclusive. 
Tertiary  -        -    J 

~  f  from  the  Maestricht  Chalk  to  the  Wealden  incld- 

2.  U-etace  -   J     giye> 

3.  Oolitic    -  from  the  Purbeck  to  the  Lias  inclusive. 

„  .  .  f  including  the  Keuper,  Muschelkalk,  and  Bunter- 

"  \      Sandstein  of  the  Germans. 

5.  Permian,  Carbonife-  "f  including  Magnesian  Limestone  (Zechstein),  Coal, 
rous,  and  Devonian  J      Mountain  Limestone,  and  Old  Red  Sandstone. 

6.  Silurian    and    Cam-  1  from  the  Upper  Silurian  to  the  oldest  fossiliferous 
brian        -        -        -  J      rocks  inclusive. 

But  the  following  more  detailed  list  of  fossiliferous  strata,  divided 
into  thirty-three  sections,  will  be  required  by  the  reader  when  he  is 
studying  our  descriptions  of  the  sedimentary  formations  given  in  the 
next  18  chapters. 

*  Palaeontology  is  the  science  which    cient,  ovra,  onta,  beings,  and  \oyos,  logos, 
treats  of  fossil  remains,  both  animal  and    a  discourse, 
vegetable.     Etym.  iraXaios,  palaios,  an- 


CH.  IX.  J  TABULAR   VIEW   OF   FOSSILIFEROUS   STRATA. 


105 


TABULAR  VIEW 

OP    THE 


FOSSILIFEROUS    STRATA, 

Showing  the  Order  of  Superposition  or  Chronological  Succession  of  the 
principal  Groups. 


Periods  and  Groups. 

1.  POST-TERTIARY. 
A.  POST-PLIOCENE. 


British  Examples. 


Foreign  Equivalents  and  Synonyms. 

I. "TERRAINS    CONTKMPORAINES, 
ET    QUATERNAIRES. 


1.  RECENT. 


fPeat  of  Great  Britain  and  Ireland, 
with  human  remains.  (Princi- 
1  pies  of  Geology,  ch.  45.) 
]  Alluvial  plains  of  the  Thames, 
i  Mersey,  and  Rother,  with  buried 
L  ships,p.i20.,andPrinciples,ch.48. 


2.  POST-PLIOCENE. 


and  with  bones  of  land  animals, 
jartly  of  extinct  species  j  no 
luman  remains. 


Part  of  the  Terrain  quaternaire  of 

French  authors. 
Modern  part  of  deltas  of  Rhine, 

Nile,  Ganges,  Mississippi,  &c. 
Modern  part  of  coral-reefs  of  Red 

Sea  and  Pacific. 
Marine  strata  inclosing  Temple 'of 

Serapis  at  Puzzuoli.  Principles, 

ch.  29. 

Freshwater  strata  inclosing  Tem- 
ple in  Cashmere.  Ibid.  9th  ed. 

p.  762. 

Part  of  Terrain  quaternaire  of 
French  authors. 

Volcanic  tuff  of  ischia.  with  living 
species  of  marine  shells  and  with- 
out human  remains  or  works  of 
art,  p.  118. 

Loess  of  the  Rhine,  with  recent 
freshwater  shells,  and  mammoth 
bones,  p.  122. 

Newer  part  of  boulder-formation  in 
Sweden,  p.  130.  Bluffs  of  Mis- 
sissippi, p.  122. 


II.  TERTIARY. 
B.  PLIOCENE. 

3,  NEWER 

PLIOCENE, 

or 
Pleistocene. 


4.  OLDER 

PLIOCENE. 


C.  MIOCENE. 


5.        MIOCENE. 


Glacial  drift  or  boulder-formation 
of  Norfolk,  p.  132.,  of  the  Clyde 
in  Scotland,p.l3l ., of  North  Wales, 

p.  137.    Norwich  Crag,  p.  155 

Cave-deposits  of  Kirkdale,  &c. 
with  bones  of  extinct  and  living 
quadrupeds,  p. 161. 


fRed  Crag  of  Suffolk,  pp.  169—171. 
•I  Coralline  crag  of  Suffolk,  pp.169  — 
.     172. 


Marine  strata  of  this  age  wanting 

in  the  British  Isles. 
Leaf-bed  of  Mull  in  the  Hebrides  ? 

p.  180. 
Lignite  of  Antrim  ?,  p.  181. 


II.  TERRAINS  TERTIAIRES. 


{Terrain  quaternaire,  diluvium. 
Terrains  tertiaires  superieurs.p.l 39. 
Glacial  drift  of  Northern  Europe, 
p.  129.  j  and  of  Northern  United 
States,  p.  140.;  and  Alpine  er- 
ratics, p.  149. 
Limestone  of  Girgenti,  p.  159. 
Australian  cave-breccias,  p.  162. 

rSubapennine  strata,  p.  174. 
.  Hills  of  Rome,  Monte  Mario,  &c. 
I     p.  17«.  and  p.  535. 
j  Antwerp  and  Normandy  crag,  p. 

LAralo- Caspian  deposits,  p.  176. 
C.  TERRAINS  TERTIAIRES  MOYENS, 

PARTIE  SUPERIEURE  ;  OR  FALUNS. 

'Falurien  superieur,  D'Orbigny. 

Faluns  of  Touraine,  p.  176. 

Part  of  Bourdeaux  beds,  p.  179. 

Bolderberg  strata  in  Belgium,  p, 
179. 

Part  of  Vienna  basin,  p.  180. 

Part,  of  Molasse,  Switzerland,  p. 
180. 

Sands  of  James  River,  and  Rich- 
mond, Virginia,  United  States, 
L  p.  182. 


106 


TABULAR    VIEW   OF 


[On.  IX. 


Periods  and  Groups. 

Z>.  EOCENE. 


6.  UPPER  EOCENE 

(lower  Miocene  of 

many  authors). 


British  Examples. 


J  Hemp 
1      Isle 


pstead  beds,  near  Yarmouth, 
of  Wight,  p.  193. 


7.  MXDDXiE  EOCENE. 


8.  LOWER  EOCENE. 

HI.  SECONDARY. 
E.  CRETACEOUS. 


'1.  Bembridge,   or  Binstead  Beds, 
Isle  of  Wight,  p.  209. 

2.  Osborne  or  St.  Helen's  Series, 
p.  211. 

3.  Headon  Series.    Ibid. 

4.  Headon  Hill  Sands,  and  Barton 
Clay,  p.  213. 

5.  Bagshot  and  Bracklesham  Beds, 
p.  214. 

.6.  Wanting?    See  p.  223. 


"1.  London  Clay  and  Bognor  Beds, 

p.  217. 
2.  Plastic  and  Mottled  Clays  and 

Sands,   and  Wolwich  Beds,    p. 

220. 
L3.  Thanet  Sands,  p.  222. 


§  UPPER  CRETACEOUS. 

Wanting  in  England. 


9.    MAESTRXCHT 
BEDS. 


1O. 


UPPER 


11.         LOWER 

"WHITE  CHAXiX. 


12.         UPPER 

CrREEKTSAXO'D. 


13.        CAUX.T. 


white  Chalk  with  Flints,  of  North 
j      and  South  Downs,  p.  240. 


f  Chalk  without  Flints,  and  Chalk 
<      Marl,  p.  240. 
I  Chalk  Marl.    Ibid. 


Loose    sand    with    bright    green 

grains,  p.  251. 
Firestone  of  Merstham 


Wight. 


Marly  Stone  with   Chert,   Isle  of 
I     Wi 


Foreign  Equivalents  and  Synonji 


Lower  part  of    Terrain  Tertiaire 

Moyen. 
Calcaire    Lacustre   Superieur  and 

Gres  de  Fontainbleau,  p.  195. 
Part  of  the   Lacustrine   strata  of 

Auvergne,  p.  195. 
Kleyn  Spawen   or  Limburg  beds, 

Belgium — Rupelian  andTongriao 

systems  of  Dumont,  p.  189. 
Mayence  basin,  p.  191. 
Part  of   brown-coal  of  Germany, 

pp.  192.  544. 
Hermsdorf   tile-clay  near  Berlin, 

p.  190. 

1.  Gypseous     Series     of     Mont- 
martre,    and    Calcaire   lacustre 
superieur,  p.  224. 

2  &  3.  Calcaire  Siliceux,  p.  226. 
2  &  3.    Grfes    de    Beauchamp,    or 

Sables  Moyens,  p.  227.     Laecken 

beds,  Belgium. 

4  &  5.  Upper  and  Middle  Calcaire 
Grossier,  p.  227. 

5.  Bruxellien,  or  Brussels  beds  of 

Dumont. 
5.  Lower    Calcaire    Grossier,    or 

Glauconie  Grossie"re,  p.  229. 

5.  Claiborne       beds,       Alabama, 
United  States,  p.  233. 

5  &  6.  Nummulitic    formation    of 
Europe,  Asia,  &c.,  p.  230. 

6.  Soissonnais  Sands,  or  Lits  Co- 
quilliers,  p.  229. 

"1.  Wanting  in  Paris  basin,  occurs 
at  Cassel,  in  French  Flanders. 

2.  Argile  Plastique  et  Lignite,  p. 
230. 

3.  Lower  Landenian  of  Belgium, 
.    in  part?,  p.  236. 

III.  TERRAINS  SECONDAIRES. 
E.  TERRAINS  CRETAC£ES. 


9.  Danien  of  D'Orbigny. 
Calcaire  pisolitique,    near    Paris, 

p.  236. 

Maestricht  Beds,  p.  238. 
Coralline  Limestone  of  Faxoe  in 

Denmark,  p.  239. 

«10.  Senonien,  D'Orbigny. 
Craie  blanche  avec  silex. 
Obere  Kreide  of  the  Germans. 
Upper    Quadersandstein?  of  the 

same. 

La  Scaglia  of  the  Italians. 
'Calcaire  a  hippurites,  Pyrennees. 
Turonien,  D'Orb.,  or,  Craie  tufeau 

of  Touraine. 
Craie  argileuse   of  some  French 

writers. 
.Upper  Planerkalk  of  Saxony. 

|~Gre:s  vert  superieur. 

I  Glauconie  crayeuse. 

\  Craie  chloritee. 

j  Cenomanien,  D'Orbigny. 

j  Lower  Quadersandstein  of  the  Ger- 

|_    mans. 


fDark  Blue  Marl,  Kent,  p.  251.          fGrds  vert  superieur  7  .          . 

1  Folkestone  Marl  or  Clay.  '  1  Glauconie  crayeuse  J 

]  Blackdown  Beds,  green  sand  and  ]  Albien,  D'Orbigny. 

L    chert,  Devonshire,  p.  252.  (.Lower  Planer  of  Saxony. 


LOWER  CRETACEOUS,  OR  NEOCOMIAN. 


fSand  with  green  matter,    Weald  f" 

of  Kent  and  Sussex,  p.  258.  |  GrSs  vert  inferieur. 


LOWER 
GREENSAHTD. 


1  Lirr.estone  (Kentish   Ra| 


J.  I  Neocomien  superieur. 


J  Sands   and    clay  with    calcareous  I  Aptien,  D'Orbigny. 
1     concretions  and  chert.  ]  Hils-conglomerat  of  Germany. 


Atherfield,  Isle  of  Wight,  p.  258. 


(.Speeton  Clay,  Yorkshire. 


Hils-thoQ  of  Brunswick. 


CH.  IX.] 

Periods  and  Groups. 

15.     WEAXiDEHT 

(Weald  Clay  and 
Hastings  Sand). 


FOSSILIFEROUS  STRATA. 


107 


British  Examples.  Foreign  Equivalents  and  Synonyms. 

Clay  with  oecasionalbands  of  lime-  I" 

stone — Weald  of  Kent,  Surrey, 

and  Sussex,  p.  261.  J  Formation  Waldienne. 

Sand  with  calcareous  grit  and  clay,  1  Neocomien  inferieur. 

—  Hastings,    Cuckfield,  Sussex, 

p.  263. 


F.  OOLITE. 
§  UPPER  OOLITE. 

16.  PURBECK,  BEDS. 

17.  PORTLAND 

BEDS. 


F.  TERRAINS  JuRASSiQUES,inpart. 


18. 


>GE 


CLAY. 
[§§  MIDDLE  OOLITE. 

19.  CORAXi-RAG. 

20.  OXFORD  CLAY. 


Upper,  Middle,  and  Lower   Pur-  fSerpulitenkalk    of    Bunker,    and 
beck,  Dorsetshire  and  Wilts,  pp.  <     associated  beds  of  the  North  Ger- 
L    man  Walderibrmation. 


294—297. 


{  P0pr.tl30lld  St°ne  8nd  P°rtland  Sand'  {  GrouPe  Portlandien  of  Beudaut. 

{Kimmeridgien,  D'Orbigny. 
^TMrria?  gryph*CS  VirgUl68'  °f 
Argiles  de    Honfleur,  E.  deBeau 
mont  et  Dufresnoy. 


|"  Calcareous  grit. 

•i  Coral. rag  or  oolitic  limestone  with 
L    corals,  Oxfordshire,  p.  303. 


oupe 

Corallien.  D'Orbigny. 
Calcaire  a  Xerinn£esof  Thurmann 
.    and  Thirria. 

superieur,     Thur- 


§§§  LOWER  OOLITE. 

21.  GREAT  or  BATH 
OOXiXTE. 


22. 


INFERIOR 
OOLITE. 


1.  Cornbrash  and  Forest  Marble,  f 

Wiltshire,  p.  306.  I  Bathonien  of  Omalius  D'Hallov. 

2.  Great     Oolite    and    Stonesfield  «{  Grand  Oolithe. 
Slate,— Bath,  Stonesfield,  pp.306.     Calcaire  de  Caen. 
310.  L 

{Fuller's  Earth,  near  Bath,  p.  315.     [" 
Calcareous  freestone,  and  yellow-)  Oolithe  inferieur. 
sands     of     Cotteswold      Hills,  j  Oolithe  ferrugineux  of  Normandy. 
Gloucestershire,  p.  31 5.  j  Oolithe  de  Bayeux. 

Dundry  Hill,  near  Bristol,  pp.  103.  I  Bajocien  of  D'Orbigny. 
315. 


G.  LIAS. 


23. 


XiXAS. 


:1.  Upper  Lias,  p.  319. 
2.  Marl-stone,  ibid. 
3.  Lower  Lias,  Ond. 


G.  TERRAINS  JURASSIQUES,  in  part. 

'].  E'tage      superieur      du     Lias, 

Thirria. 

Toarcien,  D'Orbigny. 
2.  Lias  moyen. 
Liasien,  D'Orbigny. 
3-  Calcaire  a  gryphee  arquee. 
Sinemurien,  D'Orbigny. 
CJoal-field    near    Richmond,   Vir- 
.    ginia.p.  331. 


H.  TRIAS. 

(  Upper  New  Red  Sandstone"}. 


H.  NOUVEAU  GRES  ROUGE. 


2ft.  UPPER  TRXAS. 


("Saliferousand  Gypseous  sandstones  f 

and  shales  of  Cheshire,  pp^SSS  —     Keuper  of  the  Germans, 
i  _  338-     .  4  Marnes  irisees  of  the  French. 

Bone-bed  of  Axmouth,  Devon,  p.     Saliferien,  D'Orbigny. 
L     338. 


25.  MXDDXiE  TRXAS  f 

or  <i  Wanting  in  England. 

Muschelkalk.         L 


{Muschelkalk  of  the  Germans. 
Calcaire  conchylien,  Brongniart. 
Calcaire  a  Ceratites,  Cordier. 
Conchylien,  D'Orbiguy,  (in  part). 


26.  X.O-WER  TRXAS 


;Red    and    white      Sandstone     of  TBunter-Sandstein  of  the  Germans. 
Lancashire       and        Cheshire    «!  Gr^s  bigarre  of  the  French, 
pp.  338.  339.  LConchylien,  D'Orbigny,  (in  part). 


108 


TABULAR  VIEW  OF  FOSSILIFEROUS   STRATA.         [Cn.  IX. 


British  Examples. 


27. 


Periods  and  Groups. 

IV.  PRIMARY. 

/.  PERMIAN, 
or  MAGNESIAN  LIMESTONE. 

(Lower  New  Red.') 

'1.  Concretionarylimestone  of  Dur- 
ham and  Yorkshire,  p.  354. 

2.  Brecciated  limestone,  ibid. 

3.  Fossiliferous  limestone,  p.  355. 

4.  Compact  limestone,  ibid. 

5.  Marl-slate  of  Durham,  p.  356. 

6.  Inferior   sandstones    of  various 
colours,— N.  of  England,  p.  357. 


Foreign  Equivalents  and  Synonyms. 

IV.  TERRAINS  DE  TRANSITION. 
TERRAINS  PALEOZOIQCES. 

I.  CALCAIRE  MAGNESIEN. 


PERMIAN, 

or 

IVIAGNESIAW 
LIMESTONE. 


Dolomitic  conglomerate,  —  Bristol, 
p.  357. 


K.  CARBONIFEROUS. 


1.  Stinkstein  of  Thuringia. 

2.  Rauchwacke,  ibid. 

3.  Dolomit  or  Upper  Zechstein. 

4.  Zechstein,  p.  353. 

5.  Mergel  or  Kupfer-schiefer. 

6.  Rothliegendes  of  Thuringia. 

Permian  of  Russia,  p.  358. 
Gres  des   Vosges  of  French,  (in 
part). 


K.  TERRAIN  HOUILLIER. 


28.    UPPER 

CARBONIFEROUS. 


29.    LOWER 
CARBONIFEROUS. 


f 


1.  Coal-measures,     sandstone  and 
shale  with  seams  of  coal,— West 
of  England  and  Ireland,  Chapters 
24  and  25. 

2.  Millstone  Grit,  pp-  361,  362. 


j  Coal-fields  of  the  United  States,  p. 
391. 


1.  Mountain  or  Carboniferous  lime- 
stone, p.  407.  etseq. 

2.  Lower  limestone  shale, —  Men- 
dips.       Carboniferous     slate, — 
Ireland. 

Carbonaceous   schist   with   Possi- 
.    donomya  Becheri,  p.  413. 


rl.  Calcaire     carbonifere     of     the 

French. 
1.  Bergkalk  or  Kohlenkalk  of  the 

Germans. 
1.  1'entremite     limestone,    United 

States,  p-  414. 

Kiesel-schiefer  and  Jiingere  Grau- 

wacke  of  the  Germans,  p.  413. 

Gypseous     beds      and    Encrinital 

L    limestone  of  Nova  Scoti  a,  p.  413. 


L.  DEVONIAN, 
or  OLD  RED  SANDSTONE. 


30.         UPPER 

DEVONIAN. 


31.          LOWER 

DEVONIAN. 


M.  SILURIAN. 

32.          UPPER 

SILURIAN. 


Yellow  sandstone  of  Dura    Den, 

Fife,  p.  416. 
White  sandstone  of  Elgin,  with  Te- 

lerpeton,  ibid. 
Red  sandstone  and  conglomerate, 

p.  418. 
Upper  and  middle  Devonian  of  N. 

Devon,      including      Plymouth 

limestone,  pp.  424.  426. 
Lower    Devonian    of   N.    Devon, 

North  Foreland,  p.  428. 
Arbroath  paving. stone,  pp.  416 — 

Bituminous  schists  of  Caithness,  p. 
422. 


L.  TERRAIN  DEVONIEN. 

VlBUXGRES  KOUGE. 


Russian  Devonian,  Upper  part,  p. 

429. 
Catskill  group,  United  States,  p. 

430. 

F.ifel  Limestone,  p.  428. 
Limestone  of  Villmar,  &c.,  Nassau. 


l.  Spirifer  Sandstone  and  Slate  of 

Sandberger,  p.  428. 
Older  Rhenish  Greywacke  of  Roe- 

mer,  ibid. 
Russian  Devonian,  Lower  part,  p. 

429. 


fl.  Upper  Ludlow,  p.  434. 
I  2.  Aymestry  Limestone,  p.  438. 
•>  3.  Lower  Ludlow,  ibid. 
j  4.  Wenlock  Limestone,  p.  439. 
L  5.  Wenlock  shale,  p.  441. 


M.  TERRAIN  SILURIEN. 
fNew  York  division  from  the  Up- 
I     per  Pentamerus  to  the  Niagara 
•\     Group  inclusive,  p.  448. 
I  Etages    E.    to    H.    of   Barrande, 
I    Bohemia. 


v>  n    MirmTn  <?iTTintAv  f  fNew  York  groups  from  the  Clinton 

(Beds  of  passage  between      \  Cara4d4°c  or  May  HU1  Sandstone'  \     tojh|  Gre>'  sandstone  inclusive, 
Upper  and  Lower  Silurian).  \_    p' 

f  Llandeilo  Flags  and  shale,  p.  443. 
Bala  Lin 
p.  445. 

Graptolite  Schists,  S.  of  Scotland.     *)  stages    C.    and    D.   (Barrande), 
Limestone,     Chair     of    Kildare,         Bohemia. 
Ireland.  Isiates  of  Angers,  France. 


33.          LOWER 
SILURIAN. 


tTNew  York  groups  from  the  Hud- 
slate,  f     son-Riverbeds  to  the  Calciferous 


,    j        auu-j.il*  ei  ueu»  tu  tuc  vnnjin 

J      sandstone  inclusive,  p.  448. 


N.  CAMBRIAN. 


3ft.          UPPER 

CAMBRIAN. 


35.         LOWER 

CAMBRIAN. 


f"  ["Primordial  zone  of   Barrande  in 

Bohemia,  p.  454. 

IT?      ,io    TI          vr  ,*v,   ix7i  1  Alum  Schists  of  Sweden,  p.  455. 

J  Lmgula  Flags,  North  Wales,   p.  J  Potsdam     Sandstone     0'fP  United 

I     States  and  Canada,  p.  455. 

j  Wisconsin  and  Minnesota,  lowest 


452. 
Stiper  Stones,  Shropshire. 


fossiliferous  rocks,  p.  456. 


Lowest     fossil  iferous     rocks 
Wicklow  in  Ireland,  p.  453. 


of 


CH.IX.]    ABRIDGED  TABLE   OF   FOSSILIFEROUS   STRATA.      109 


ABRIDGED  TABLE  OF  FOSSILIFEROUS  STRATA. 


1.  RECENT. 

2.  POST-PLIOCENE. 

3.  NEWER   PLIOCENE. 

4.  OLDER   PLIOCENE. 

5.  MIOCENE. 

6.  UPPER   EOCENE. 

7.  MIDDLE   EOCENE. 

8.  LOWER    EOCENE. 

9.  MAESTRICHT    BEDS. 

10.  UPPER  WHITE    CHALK. 

11.  LOWER   WHITE    CHALK. 

12.  UPPER    GREENSAND. 

13.  GAULT.      * 

14.  LOWER    GREENSAND. 

15.  WEALDEN. 

16.  PURBECK     BEDS. 

17.  PORTLAND    STONE. 

18.  KIMMERIDGE  CLAY. 

19.  CORAL  RAG. 

20.  OXFORD   CLAY. 

21.  GREAT  or  BATH  OOLITE. 

22.  INFERIOR    OOLITE. 

23.  LIAS. 

24.  UPPER   TRIAS. 

25.  MIDDLE   TRIAS,    or 

MUSCHELKALK. 

26.  LOWER  TRIAS. 


POST-TERTIARY. 

.  PLIOCENE. 

MIOCENE. 

EOCENE. 


CRETACEOUS. 


JURASSIC. 


TRIASSIC. 


>*    d 

05       ^ 

M 

W      3 


CO 


27.  PERMIAN, 
MAGNESIAN  LIMESTONE 

28.  COAL-MEASURES. 

29.  CARBONIFEROUS 

LIMESTONE. 

30.  UPPER  1 

^DEVONIAN. 

31.  LOWERj 

32.  UPPER  -| 

^SILURIAN. 

33.  LOWER/ 

34.  UPPER 


CARBONIFEROUS. 


DEVONIAN. 


SILURIAN. 


CAMBRIAN. 


110  PRINCIPLES   OF    CLASSIFICATION  [Cn.  X. 

CHAPTER  X. 

CLASSIFICATION   OF   TERTIARY  FORMATIONS. POST-PLIOCENE   GROUP. 

General  principles  of  classification  of  tertiary  strata — Detached  formations  scattered 
over  Europe — Strata  of  Paris  and  London — More  modern  groups — Peculiar 
difficulties  in  determining  the  chronology  of  tertiary  formations  —  Increasing 
proportion  of  living  species  of  shells  in  strata  of  newer  origin  —  Terms  Eocene, 
Miocene,  and  Pliocene — Post-Pliocene  strata — Eecent  or  human  period  —  Older 
Post- Pliocene  formations  of  Naples,  Uddevalla,  and  Norway — Ancient  upraised 
delta  of  the  Mississippi — Loess  of  the  Rhine. 

BEFORE  describing  the  most  modern  of  the  sets  of  strata  enumerated 
in  the  Tables  given  at  the  end  of  the  last  chapter,  it  will  be  necessary 
to  say  something  generally  of  the  mode  of  classifying  the  formations 
called  tertiary. 

The  name  of  tertiary  has  been  given  to  them,  because  they  are  all 
posterior  in  date  to  the  rocks  termed  "  secondary,"  of  which  the  chalk 
constitutes  the  newest  group.  These  tertiary  strata  were  at  first 
confounded,  as  before  stated,  p.  91.,  with  the  superficial  alluviums  of 
Europe  ;  and  it  was  long  before  their  real  extent  and  thickness,  and 
the  various  ages  to  which  they  belong,  were  fully  recognized.  They 
were  observed  to  occur  in  patches,  some  of  freshwater,  others  of 
marine  origin,  their  geographical  area  being  usually  small  as  com- 
pared to  the  secondary  formations,  and  their  position  often  suggesting 
the  idea  of  their  having  been  deposited  in  different  bays,  lakes,  es- 
tuaries, or  inland  seas,  after  a  large  portion  of  the  space  now  occupied 
by  Europe  had  already  been  converted- into  dry  land. 

The  first  deposits  of  this  class,  of  which  the  characters  were  ac- 
curately determined,  were  those  occurring  in  the  neighbourhood  of 
Paris,  described  in  1810  by  MM.  Cuvier  and  Brongniart.  They 
were  ascertained  to  consist  of  successive  sets  of  strata,  some  of 
marine,  others  of  freshwater  origin,  lying  one  upon  the  other.  The 
fossil  shells  and  corals  were  perceived  to  be  almost  all  of  unknown 
species,  and  to  have  in  general  a  near  affinity  to  those  now  inhabiting 
warmer  seas.  The  bones  and  skeletons  of  land  animals,  some  of 
them  of  large  size,  and  belonging  to  more  than  forty  distinct  species, 
were  examined  by  Cuvier,  and  declared  by  him  not  to  agree  specifi- 
cally, nor  even  for  the  most  part  generically,  with  any  hitherto  ob- 
served in  the  living  creation. 

Strata  were  soon  afterwards  brought  to  light  in  the  vicinity  of 
London,  and  in  Hampshire,  which,  although  dissimilar  in  mineral 
composition,  were  justly  inferred  by  Mr.  T.  Webster  to  be  of  the 
same  age  as  those  of  Paris,  because  the  greater  number  of  the  fossil 
shells  were  specifically  identical.  For  the  same  reason,  rocks  found 
on  the  Gironde,  in  the  South  of  France,  and  at  certain  points  in 
the  North  of  Italy,  were  suspected  to  be  of  contemporaneous  origin. 


CH.  X.]  OF   TERTIARY   FORMATION".  Ill 

A  variety  of  deposits  were  afterwards  found  in  other  parts  of 
Europe,  all  reposing  immediately  on  rocks  as  old  or  older  than  the 
chalk,  and  which  exhibited  certain  general  characters  of  resemblance 
in  their  organic  remains  to  those  previously  observed  near  Paris  and 
London.  An  attempt  was  therefore  made  at  first  to  refer  the  whole 
to  one  period ;  and  when  at  length  this  seemed  impracticable,  it  was 
contended  that  as  in  the  Parisian  series  there  were  many  subordinate 
formations  of  considerable  thickness  which  must  have  accumulated 
one  after  the  other,  during  a  great  lapse  of  time,  so  the  various 
patches  of  tertiary  strata  scattered  over  Europe  might  correspond  in 
age,  some  of  them  to  the  older,  and  others  to  the  newer,  subdivisions 
of  the  Parisian  series. 

This  error,  though  almost  unavoidable  on  the  part  of  those  who 
made  the  first  generalizations  in  this  branch  of  geology,  retarded 
seriously  for  some  years  the  progress  of  classification.  A  more  scru- 
pulous attention  to  specific  distinctions,  aided  by  a  careful  regard  to 
the  relative  position  of  the  strata  containing  them,  led  at  length  to 
the  conviction  that  there  were  formations  both  marine  and  freshwater 
of  various  ages,  and  all  newer  than  the  strata  of  the  neighbourhood  of 
Paris  and  London. 

One  of  the  first  steps  in  this  chronological  reform  was  made  in 
1811,  by  an  English  naturalist,  Mr.  Parkinson,  who  pointed  out  the 
fact  that  certain  shelly  strata,  provincially  termed  "  Crag  "  in  Suffolk, 
lie  decidedly  over  a  deposit  which  was  the  continuation  of  the  blue 
clay  of  London.  At  the  same  time  he  remarked  that  the  fossil  tes- 
tacea  in  these  newer  beds  were  distinct  from  those  of  the  blue  clay, 
and  that  while  some  of  them  were  of  unknown  species,  others  were 
identical  with  species  now  inhabiting  the  British  seas. 

Another  important  discovery  was  soon  afterwards  made  by  Brocchi 
in  Italy,  who  investigated  the  argillaceous  and  sandy  deposits,  replete 
with  shells,  which  form  a  low  range  of  hills,  flanking  the  Apennines 
on  both  sides,  from  the  plains  of  the  Po  to  Calabria.  These  lower 
hills  were  called  by  him  the  Subapennines,  and  were  formed  of  strata 
chiefly  marine,  and  newer  than  those  of  Paris  and  London. 

Another  tertiary  group  occurring  in  the  neighbourhood  of  Bordeaux 
and  Dax,  in  the  south  of  France,  was  examined  by  M.  de  Basterot 
in  1825,  who  described  and  figured  several  hundred  species  of  shells, 
which  differed  for  the  most  part  both  from  the  Parisian  series  and 
those  of  the  Subapennine  hills.  It  was  soon,  therefore,  suspected 
that  this  fauna  might  belong  to  a  period  intermediate  between  that  of 
the  Parisian  and  Subapennine  strata,  and  it  was  not  long  before  the 
evidence  of  superposition  was  brought  to  bear  in  support  of  this 
opinion  ;  for  other  strata,  contemporaneous  with  those  of  Bordeaux, 
were  observed  in  one  district  (the  Valley  of  the  Loire),  to  overlie  the 
Parisian  formation,  and  in  another  (in  Piedmont)  to  underlie  the  Sub- 
apennine beds.  The  first  example  of  these  was  pointed  out  in  1829 
by  M.  Desnoyers,  who  ascertained  that  the  sand  and  marl  of  marine 
origin  called  Faluns,  near  Tours,  in  the  basin  of  the  Loire,  full  of  sea- 
shells  .and  corals,  rested  upon  a  lacustrine  formation,  which  constitutes 


112  PRINCIPLES   OF   CLASSIFICATION.  [Cn.  X. 

the  uppermost  subdivision  of  the  Parisian  group,  extending  con- 
tinuously throughout  a  great  table-land  intervening  between  the  basin 
of  the  Seine  and  that  of  the  Loire.  The  other  example  occurs  in 
Italy,  where  strata,  containing  many  fossils  similar  to  those  of  Bor- 
deaux, were  observed  by  Bonelli  and  others  in  the  environs  of  Turin, 
subjacent  to  strata  belonging  to  the  Subapennine  group  of  Brocchi. 

Without  pretending  to  give  a  complete  sketch  of  the  progress  of 
discovery,  I  may  refer  to  the  facts  above  enumerated,  as  illustrating 
the  course  usually  pursued  by  geologists  when  they  attempt  to  found 
new  chronological  divisions.  The  method  bears  some  analogy  to  that 
pursued  by  the  naturalist  in  the  construction  of  genera,  when  he 
selects  a  typical  species,  and  then  classes  as  congeners  all  other  species 
of  animals  and  plants  which  agree  with  this  standard  within  certain 
limits.  The  genera  A.  and  C.  having  been  founded  on  these  prin- 
ciples, a  new  species  is  afterwards  met  with,  departing  widely  both 
from  A.  and  C.,  but  in  many  respects  of  an  intermediate  character. 
For  this  new  type  it  becomes  necessary  to  institute  the  new  genus  B., 
in  which  are  included  all  species  afterwards  brought  to  light,  which 
agree  more  nearly  with  B.  than  with  the  types  of  A.  or  C.  In  like 
manner  a  new  formation  is  met  with  in  geology,  and  the  characters 
of  its  fossil  fauna  and  flora  investigated.  From  that  moment  it  is 
considered  as  a  record  of  a  certain  period  of  the  earth's  history,  and  a 
standard  to  which  other  deposits  may  be  compared.  If  any  are  found 
containing  the  same  or  nearly  the  same  organic  remains,  and  occupy- 
ing the  same  relative  position,  they  are  regarded  in  the  light  of  con- 
temporary annals.  All  such  monuments  are  said  to  relate  to  one 
period,  during  which  certain  events  occurred,  such  as  the  formation 
of  particular  rocks  by  aqueous  or  volcanic  agency,  or  the  continued 
existence  and  fossilization  of  certain  tribes  of  animals  and  plants. 
When  several  of  these  periods  have  had  their  true  places  assigned  to 
them  in  a  chronological  series,  others  are  discovered  which  it  becomes 
necessary  to  intercalate  between  those  first  known  ;  and  the  difficulty 
of  assigning  clear  lines  of  separation  must  unavoidably  increase  in 
proportion  as  chasms  in  the  past  history  of  the  globe  are  filled  up. 

Every  zoologist  and  botanist  is  aware  that  it  is  a  comparatively 
easy  task  to  establish  genera  in  departments  which  have  been  en- 
riched with  only  a  small  number  of  species,  and  where  there  is  as 
yet  no  tendency  in  one  set  of  clfaracters  to  pass  almost  insensibly,  by 
a  multitude  of  connecting  links,  into  another.  They  also  know  that 
the  difficulty  of  classification  augments,  and  that  the  artificial  nature 
of  their  divisions  becomes  more  apparent,  in  proportion  to  the  increased 
number  of  objects  brought  to  light.  But  in  separating  families  and 
genera,  they  have  no  other  alternative  than  to  avail  themselves  of 
such  breaks  as  still  remain,  or  of  every  hiatus  in  the  chain  of  ani- 
mated beings  which  is  not  yet  filled  up.  So  in  geology,  we  may  be 
eventually  compelled  to  resort  to  sections  of  time  as  arbitrary,  and  as 
purely  conventional,  as  those  which  divide  the  history  of  human 
events  into  centuries.  But  in  the  present  state  of  our  knowledge,  it 
is  more  convenient  to  use  the  interruptions  which  still  occur  in  the 


CH.  X.]  OF   TERTIARY   FORMATIONS.  113 

regular  sequence  of  geological  monuments,  as  boundary  lines  between 
our  principal  groups  or  periods,  even  though  the  groups  thus  esta- 
blished are  of  very  unequal  value. 

The  isolated  position  of  distinct  tertiary  deposits  in  different  parts 
of  Europe  has  been  already  alluded  to.  In  addition  to  the  difficulty 
presented  by  this  want  of  continuity  when  we  endeavour  to  settle 
the  chronological  relations  of  these  deposits,  another  arises  from  the 
frequent  dissimilarity  in  mineral  character  of  strata  of  contempora- 
neous date,  such,  for  example,  as  those  of  London  and  Paris  before 
mentioned.  The  identity  or  non-identity  of  species  is  also  a  criterion 
which  often  fails  us.  For  this  we  might  have  been  prepared,  for  we 
have  already  seen,  that  the  Mediterranean  and  Red  Sea,  although 
within  70  miles  of  each  other,  on  each  side  of  the  Isthmus  of  Suez, 
have  each  their  peculiar  fauna ;  and  a  marked  difference  is  found  in 
the  four  groups  of  testacea  now  living  in  the  Baltic,  English  Channel, 
Black  Sea,  and  Mediterranean,  although  all  these  seas  have  many 
species  in  common.  In  like  manner  a  considerable  diversity  in  the 
fossils  of  different  tertiary  formations,  which  have  been  thrown 
down  in  distinct  seas,  estuaries,  bays,  and  lakes,  does  not  always 
imply  a  distinctness  in  the  times  when  they  were  produced,  but  may 
have  arisen  Jfrom  climate  and  conditions  of  physical  geography  wholly 
independent  of  time.  On  the  other  hand,  it  is  now  abundantly  clear, 
as  the  result  of  geological  investigation,  that  different  sets  of  tertiary 
strata,  immediately  superimposed  upon  each  other,  contain  distinct 
imbedded  species  of  fossils,  in  consequence  of  fluctuations  which  have 
been  going  on  in  the  animate  creation,  and  by  which  in  the  course  of 
ages  one  state  of  things  in  the  organic  world  has  been  substituted  for 
another  wholly  dissimilar.  It  has  also  been  "shown  that  in  propor- 
tion as  the  age  of  a  tertiary  deposit  is  more  modern,  so  is  its  fauna 
more  analogous  to  that  now  in  being  in  the  neighbouring  seas.  It  is 
this  law  of  a  nearer  agreement  of  the  fossil  testacea  with  the  species 
now  living,  which  may  often  furnish  us  with  a  clue  for  the  chrono- 
logical arrangement  of  scattered  deposits,  where  we  cannot  avail  our- 
selves of  any  one  of  the  three  ordinary  chronological  tests ;  namely, 
superposition,  mineral  character,  and  the  specific  identity  of  the 
fossils.  • 

Thus,  for  example,  on  the  African  border  of  the  Eed  Sea,  at  the 
height  of  40  feet,  and  sometimes  more,  above  its  level,  a  white  calca- 
reous formation  has  been  observed,  containing  several  hundred  species 
of  shells  differing  from  those  found  in  the  clay  and  volcanic  tuff  of 
the  country  round  Naples,  and  of  the  contiguous  island  of  Ischia. 
Another  deposit  has  been  found  at  Uddevalla,  in  Sweden,  in  which 
the  shells  do  not  agree  with  those  found  near  Naples.  But  although 
in  these  three  cases  there  may  be  scarcely  a  single  shell  common  to 
the  three  different  deposits,  we  do  not  hesitate  to  refer  them  all  to 
one  period  (the  Post-Pliocene),  because  of  the  very  close  agreement 
of  the  fossil  species  in  every  instance  with  those  now  living  in  the 
contiguous  seas. 

To  take  another  example,  where  the  fossil  fauna  recedes  a  few 

I 


114          CLASSIFICATION   OF   TERTIARY   FORMATIONS.       [Cn.  X. 

steps  farther  back  from  our  own  times.  We  may  compare,  first,  the 
beds  of  loam  and  clay  bordering  the  Clyde  in  Scotland  (called  glacial 
by  some  geologists)  ;  secondly,  others  of  fluvio-marine  origin  near 
Norwich  ;  and,  lastly,  a  third  set  often  rising  to  considerable  heights  in 
Sicily:  and  we  discover  that  in  every  case  more  than  three-fourths  of 
the  shells  agree  with  species  still  living,  while  the  remainder  are 
extinct.  Hence  we  may  conclude  that  all  these,  greatly  diversified  as 
are  their  organic  remains,  belong  to  one  and  the  same  era,  or  to  a 
period  immediately  antecedent  to  the  Post-Pliocene,  because  there 
has  been  time  in  each  of  the  areas  alluded  to  for  an  equal  or  nearly 
equal  amount  of  change  in  the  marine  testaceous  fauna.  Contempo- 
raneousness of  origin  is  inferred  in  these  cases,  in  spite  of  the  most 
marked  differences  of  mineral  character  or  organic  contents,  from  a 
similar  degree  of  divergence  in  the  shells  from  those  now  living  in  the 
adjoining  seas.  The  advantage  of  such  a  test  consists  in  supplying 
us  with  a  common  point  of  departure  in  all  countries,  however  remote. 

But  the  farther  we  recede  from  the  present  times,  and  the  smaller 
the  relative  number  of  recent  as  compared  with  extinct  species  in 
the  tertiary  deposits,  the  less  confidence  can  we  place  in  the  exact 
value  of  such  a  test,  especially  when  comparing  the  strata  of  very 
distant  regions  ;  for  we  cannot  presume  that  the  ra^jp  of  former 
alterations  in  the  animate  world,  or  the  continual  going  out  and 
coming  in  of  species,  has  been  every  where  exactly  equal  in  equal 
quantities  of  time.  The  form  of  the  land  and  sea,  and  the  climate, 
may  have  changed  more  in  one  region  than  in  another  ;  and  conse- 
quently there  may  have  been  a  more  rapid  destruction  and  renova- 
tion of  species  in  one  part  of  the  globe  than  elsewhere.  Consider- 
ations of  this  kind  should  undoubtedly  put  us  on  our  guard  against 
relying  too  implicitly  on  the  accuracy  of  this  test  ;  yet  it  can  never 
fail  to  throw  great  light  on  the  chronological  relations  of  tertiary 
groups  with  each  other,  and  with  the  Post-Pliocene  period. 

We  may  derive  a  conviction  of  this  truth  not  only  from  a  study  of 
geological  monuments  of  all  ages,  but  also  by  reflecting  on  the  ten- 
dency which  prevails  in  the  present  state  of  nature  to  a  uniform  rate 
of  simultaneous  fluctuation  in  the  flora  and  fauna  of  the  whole  globe. 
The  grounds  of  such  a  doctrine  cannot  be  discussed  here,  and  I 
have  explained  them  at  some  length  in  the  third  Book  of  the 
Principles  of  Geology,  where  the  causes  of  the  successive  extinction 
of  species  are  considered.  It  will  be  there  seen  that  each  local  change 
in  climate  and  physical  geography  is  attended  with  the  immediate 
increase  of  certain  species,  and  the  limitation  of  the  range  of  others. 
A  revolution  thus  effected  is  rarely,  if  ever,  confined  to  a  limited 
space,  or  to  one  geographical  province  of  animals  or  plants,  but 
affects  several  other  surrounding  and  contiguous  provinces.  In  each 
of  these,  moreover,  analogous  alterations  of  the  stations  and  habit- 
ations of  species  are  simultaneously  in  progress,  reacting  in  the 
manner  already  alluded  to  on  the  first  province.  Hence,  long  before 
the  geography  of  any  particular  district  can  be  essentially  altered, 
the  flora  and  fauna  throughout  the  world  will  have  been  materially 


CH.  X.]  FOSSIL    SHELLS.  115 

modified  by  countless  disturbances  in  the  mutual  relation  of  the  various 
members  of  the  organic  creation  to  each  other.  To  assume  that  in 
one  large  area  inhabited  exclusively  by  a  single  assemblage  of  species 
any  important  revolution  in  physical  geography  can  be  brought  about, 
while  other  areas  remain  stationary  in  regard  to  the  position  of  land 
and  sea,  the  height  of  mountains,  and  so  forth,  is  a  most  improbable 
hypothesis,  wholly  opposed  to  what  we  know  of  the  laws  now  governing 
the  aqueous  and  igneous  causes.  On  the  other  hand,  even  were  this 
conceivable,  the  communication  of  heat  and  cold  between  different 
parts  of  the  atmosphere  and  ocean  is  so  free  and  rapid,  that  the  tempe- 
rature of  certain  zones  cannot  be  materially  raised  or  lowered  without 
others  being  immediately  affected ;  and  the  elevation  or  diminution  in 
height  of  an  important  chain  of  mountains  or  the  submergence  of  a 
wide  tract  of  land  would  modify  the  climate  even  of  the  antipodes. 

It  will  be  observed  that  in  the  foregoing  allusions  to  organic  re- 
mains, the  testacea  or  the  shell-bearing  mollusca  are  selected  as  the 
most  useful  and  convenient  class  for  the  purposes  of  general  classifi- 
cation. In  the  first  place,  they  are  more  universally  distributed 
through  strata  of  every  age  than  any  other  organic  bodies.  Those 
families  of  fossils  which  are  of  rare  and  casual  occurrence  are  abso- 
lutely of  no  avail  in  establishing  a  chronological  arrangement.  If  we 
have  plants  alone  in  one  group  of  strata  and  the  bones  of  mammalia 
in  another,  we  can  draw  no  conclusion  respecting  the  affinity  or  dis- 
cordance of  the  organic  beings  of  the  two  epochs  compared  ;  and  the 
same  may  be  said  if  we  have  plants  and  vertebrated  animals  in  one 
series  and  only  shells  in  another.  Although  corals  are  more  abun- 
dant, in  a  fossil  state,  than  plants,  reptiles,  or  fish,  they  are  still  rare 
when  contrasted  with  shells,  especially  in  the^European  tertiary  for- 
mations. The  utility  of  the  testacea  is,  moreover,  enhanced  by  the 
circumstance  that  some  forms  are  proper  to  the  sea,  others  to  the 
land,  and  others  to  freshwater.  Rivers  scarcely  ever  fail  to  carry  ( 
down  into  their  deltas  some  land  shells,  together  with  species  which 
are  at  once  fluviatile  and  lacustrine.  By  this  means  we  learn  what 
terrestrial,  freshwater,  and  marine  species  co-existed  at  particular 
eras  of  the  past :  and  having  thus  identified  strata  formed  in  seas 
with  others  which  originated  contemporaneously  in  inland  lakes,  we 
are  then  enabled  to  advance  a  step  farther,  and  show  that  certain 
quadrupeds  or  aquatic  plants,  found  fossil  in  lacustrine  formations, 
inhabited  the  globe  at  the  same  period  when  certain  fish,  reptiles,  and 
zoophytes  lived  in  the  ocean. 

Among  other  characters  of  the  molluscous  animals,  which  render 
them  extremely  valuable  in  settling  chronological  questions  in  geology, 
may  be  mentioned,  first,  the  wide  geographical  range  of  many  species  ; 
and,  secondly,  what  is  probably  a  consequence  of  the  former,  the  great 
duration  of  species  in  this  class,  for  they  appear  to  have  surpassed  in 
longevity  the  greater  number  of  the  mammalia  and  fish.  Had  each 
species  inhabited  a  very  limited  space,  it  could  never,  when  imbedded 
in  strata,  have  enabled  the  geologist  to  identify  deposits  at  distant 
points  ;  or  had  they  each  lasted  but  for  a  brief  period,  they  could  have 

i  2 


116  FOSSIL    SHELLS.  [Cn.  X. 

thrown  no  light  on  the  connection  of  rocks  placed  far  from  each  other 
in  the  chronological,  or,  as  it  is  often  termed,  vertical  series. 

Many  authors  have  divided  the  European  tertiary  strata  into  three 
groups  —  lower,  middle,  and  upper  ;  the  lower  comprising  the  oldest 
formations  of  Paris  and  London  before  mentioned ;  the  middle  those 
of  Bordeaux  and  Touraine ;  and  the  upper  all  those  newer  than  the 
middle  group. 

When  engaged  in  1828  in  preparing  my  work  on  the  Principles  of 
Geology,  I  conceived  the  idea  of  classing  the  whole  series  of  tertiary 
strata  in  four  groups,  and  endeavouring  to  find  characters  for  each, 
expressive  of  their  different  degrees  of  affinity  to  the  living  fauna. 
With  this  view,  I  obtained  information  respecting  the  specific  iden- 
tity of  many  tertiary  and  recent  shells  from  several  Italian  naturalists, 
and  among  others  from  Professors  Bonelli,  Guidotti,  and  Costa. 
Having  in  1829  become  acquainted  with  M.  Deshayes,  of  Paris, 
already  well  known  by  his  conchological  works,  I  learnt  from  him 
that  he  had  arrived,  by  independent  researches,  and  by  the  study  of  a 
large  collection  of  fossil  and  recent  shells,  at  very  similar  views  re- 
specting the  arrangement  of  tertiary  formations.  At  my  request  he 
drew  up,  in  a  tabular  form,  lists  of  all  the  shells  known  to  him  to  occur 
both  in  some  tertiary  formation  and  in  a  living  state,  for  the  express 
purpose  of  ascertaining  the  proportional  number  of  fossil  species  iden- 
tical with  the  recent  which  characterized  successive  groups ;  and  this 
table,  planned  by  us  in  common,  was  published  by  me  in  1833.*  The 
number  of  tertiary  fossil  shells  examined  by  M.  Deshayes  was  about 
3000 ;  and  the  recent  species  with  which  they  had  been  compared 
about  5000.  The  result  then  arrived  at  was,  that  in  the  lower  ter- 
tiary strata,  or  those  of  London  and  Paris,  there  were  about  3|  per 
cent,  of  species  identical  with  recent ;  in  the  middle  tertiary  of  the 
Loire  and  Gironde  about  17  per  cent. ;  and  in  the  upper  tertiary  or 
Subapennine  beds,  from  35  to  50  per  cent.  In  formations  still  more 
modern,  some  of  which  I  had  particularly  studied  in  Sicily,  where 
they  attain  a  vast  thickness  and  elevation  above  the  sea,  the  number 
of  species  identical  with  those  now  living  was  believed  to  be  from 
90  to  95  per  cent.  For  the  sake  of  clearness  and  brevity,  I  proposed 
to  give  short  technical  names  to  these  four  groups,  or  the  periods  to 
which  they  respectively  belonged.  I  called  the  first  or  oldest  of  them 
Eocene,  the  second  Miocene,  the  third  Older  Pliocene,  and  the  last 
or  fourth  Newer  Pliocene.  The  first  of  the  above  terms,  Eocene,  is 
derived  from  TJWC,  eos,  dawn,  and  KO.IVOQ,  cainos,  recent,  because  the 
fossil  shells  of  this  period  contain  an  extremely  small  proportion  of 
living  species,  which  may  be  looked  upon  as  indicating  the  dawn  of 
the  existing  state  of  the  testaceous  fauna,  no  recent  species  having 
been  detected  in  the  older  or  secondary  rocks. 

The  term  Miocene  (from  fietov,  meion,  less,  and  KO.IVOQ,  cainos, 
recent)  is  intended  to  express  a  minor  proportion  of  recent  species 
(of  testacea),  the  term  Pliocene  (from  rXeiov,  pleion,  more,  and  KO.IVOS, 

*  See  Prine.  of  Geol.  vol.  iii  1st  ed. 


CH.  X.]  POST-PLIOCENE  FORMATIONS.  117 

cainos,  recent]  a  comparative  plurality  of  the  same.  It  may  assist 
tiie  memory  of  students  to  remind  them,  that  the  Miocene  contain  a 
minor  proportion,  and  7^/iocene  a  comparative  p/urality  of  recent 
species  ;  and  that  the  greater  number  of  recent  species  always  implies 
the  more  modern  origin  of  the  strata. 

It  has  sometimes  been  objected  to  this  nomenclature  that  certain 
species  of  infusoria  found  in  the  chalk  are  still  existing,  and,  on  the 
other  hand,  the  Miocene  and  Older  Pliocene  deposits  often  contain  the 
remains  of  mammalia,  reptiles,  and  fish,  exclusively  of  extinct  species. 
But  the  reader  must  bear  in  mind  that  the  terms  Eocene,  Miocene, 
and  Pliocene  were  originally  invented  with  reference  purely  to  con- 
chological  data,  and  in  that  sense  have  always  been  and  are  still  used 
by  me. 

The  distribution  of  the  fossil  species  from  which  the  results  before 
mentioned  were  obtained  in  1830  by  M.  Deshayes  was  as  follows :  — 

In  the  formations  of  the  Pliocene  periods,  older  and  newer    -      777 
In  the  Miocene         -  -  -  -  -  -     1021 

In  the  Eocene  -  -  ...»  -  -     1238 

3036 

Since  the  year  1830,  the  number  of  new  living  species  obtained 
from  different  parts  of  the  globe  has  been  exceedingly  great,  supplying 
fresh  data  for  comparison,  and  enabling  the  paleontologist  to  correct 
many  erroneous  identifications  of  fossil  and  recent  forms.  New 
species  also  have  been  collected  in  abundance  from  tertiary  formations 
of  every  age,  while  newly  discovered  groups  of  strata  have  filled  up 
gaps  in  the  previously  known  series.  Hence  modifications  and  re- 
forms have  been  called  for  in  the  classification  first  proposed.  The 
Eocene,  Miocene,  and  Pliocene  periods  have  been  made  to  comprehend 
certain  sets  of  strata  of  which  the  fossils  do  not  always  conform  strictly 
in  the  proportion  of  recent  to  extinct  species  with  the  definitions  first 
given  by  me,  or  which  are  implied  in  the  etymology  of  those  terms. 
Of  these  and  other  innovations  I  shall  treat  more  fully  in  the  14th 
and  15th  chapters. 

POST-PLIOCENE  FORMATIONS. 

I  have  adopted  the  term  Post-Pliocene  for  those  strata  which  are 
sometimes  called  post-tertiary  or  modern,  and  which  are  characterized 
by  having  all  the  imbedded  fossil  shells  identical  with  species  now 
living,  whereas  even  the  Newer  Pliocene,  or  newest  of  the  tertiary 
deposits  above  alluded  to,  contain  always  some  small  proportion  of 
shells  of  extinct  species. 

These  modern  formations,  thus  defined,  comprehend  not  only  those 
strata  which  can  be  shown  to  have  originated  since  the  earth  was 
inhabited  by  man,  but  also  deposits  of  far  greater  extent  and  thick- 
ness, in  which  no  signs  of  man  or  his  works  can  be  detected.  In  some 
of  these,  of  a  date  long  anterior  to  the  times  of  history  and  tradition, 
the  bones  of  extinct  quadrupeds  have  been  met  with  of  species  which 
probably  never  co-existed  with  the  human  race,  as,  for  example,  the 

i  3 


118  POST-PLIOCENE    FOEMATIONS.  [Cn.  X. 

mammoth,  mastodon,  megatherium,  and  others,  and  yet  the  shells  are 
the  same  as  those  now  living. 

That  portion  of  the  post-pliocene  group  which  belongs  to  the 
human  epoch,  and  which  is  sometimes  called  Recent,  forms  a  very 
unimportant  feature  in  the  geological  structure  of  the  earth's  crust. 
I  have  shown,  however,  in  "The  Principles,"  where  the  recent  changes 
of  the  earth  illustrative  of  geology  are  described  at  length,  that 
the  deposits  accumulated  at  the  bottom  of  lakes  and  seas  within  the 
last  4000  or  5000  years  can  neither  be  insignificant  in  volume  or 
extent.  They  lie  hidden,  for  the  most  part,  from  our  sight ;  but  we 
have  opportunities  of  examining  them  at  certain  points  where  newly- 
gained  land  in  the  deltas  of  rivers  has  been  cut  through  during  floods, 
or  where  coral  reefs  are  growing  rapidly,  or  where  the  bed  of  a  sea 
or  lake  has  been  heaved  up  by  subterranean  movements  and  laid 
dry.  Their  age  may  be  recognized  either  by  our  finding  in  them 
the  bones  of  man  in  a  fossil  state,  that  is  to  say,  imbedded  in  them 
by  natural  causes,  or  by  their  containing  articles  fabricated  by  the 
hands  of  man. 

Thus  at  Puzzuoli,  near  Naples,  marine  strata  are  seen  containing 
fragments  of  sculpture,  pottery,  and  the  remains  of  buildings,  together 
with  innumerable  shells  retaining  in  part  their  colour,  and  of  the 
same  species  as  those  now  inhabiting  the  Bay  of  Baise.  The  up- 
permost of  these  beds  is  about  20  feet  above  the  level  of  the  sea. 
Their  emergence  can  be  proved  to  have  taken  place  since  the  be- 
ginning of  the  sixteenth  century.  *  Now  here,  as  in  almost  every 
instance  where  any  alterations  of  level  have  been  going  on  in 
historical  periods,  it  is  found  that  rocks  containing  shells,  all,  or 
nearly  all,  of  which  still  inhabit  the  neighbouring  sea,  may  be  traced 
for  some  distance  into  the  interior,  and  often  to  a  considerable 
elevation  above  the  level  of  the  sea.  Thus,  in  the  country  round 
Naples,  the  post-pliocene  strata,  consisting  of  clay  and  horizontal 
beds  of  volcanic  tuff,  rise  at  certain  points  to  the  height  of  1500  feet. 
Although  the  marine  shells  are  exclusively  of  living  species,  they  aye 
not  accompanied  like  those  on  the  coast  at  Puzzuoli  by  any  traces  6f 
man  or  his  works.  Had  any  such  been  discovered,  it  would  hape 
afforded  to  the  antiquary  and  geologist  matter  of  great  surprise, 
since  it  would  have  shown  that  man  was  an  inhabitant  of  that  part 
of  the  globe,  while  the  materials  composing  the  present  hills  and 
plains  of  Campania  were  still  in  the  progress  of  deposition  at  the 
bottom  of  the  sea ;  whereas  we  know  that  for  nearly  3000  years,  or 
from  the  times  of  the  earliest  Greek  colonists,  no  material  revolution 
in  the  physical  geography  of  that  part  of  Italy  has  occurred. 

In  Ischia,  a  small  island  near  Naples,  composed  in  like  manner  of 
marine  and  volcanic  formations,  Dr.  Philippi  collected  in  the  stra- 
tified tuff  and  clay  ninety-two  species  of  shells  of  existing  species.  In 
the  centre  of  Ischia,  the  lofty  hill  called  Epomeo,  or  San  Nicola,  is 
composed  of  greenish  indurated  tuff,  of  a  prodigious  thickness,  inter- 

*  See  Principles,  Index,  "  Serapis." 


Cii.  X.]  POST-PLIOCENE   FORMATIONS.  119 

stratified  in  some  parts  with  marl,  and  here  and  there  with  great 
beds  of  solid  lava.  Visconti  ascertained  by  trigonometrical  measure- 
ment that  this  mountain  was  2605  feet  above  the  level  of  the  sea. 
Not  far  from  its  summit,  at  the  height  of  about  2000  feet,  as  also 
near  Moropano,  a  village  only  100  feet  lower,  on  the  southern  de- 
clivity of  the  mountain,  I  collected,  in  1828,  many  shells  of  species 
now  inhabiting  the  neighbouring  gulf.  It  is  clear,  therefore,  that  the 
great  mass  of  Epomeo  was  not  only  raised  to  its  present  height,  but 
was  also  formed  beneath  the  waters,  within  the  post-pliocene  period. 
It  is  a  fact,  however,  of  no  small  interest,  that  the  fossil  shells  from 
these  modern  tuffs  of  the  volcanic  region  surrounding  the  Bay  of 
Baia?,  although  none  of  them  extinct,  indicate  a  slight  want  of  corre- 
spondence between  the  ancient  fauna  and  that  now  inhabiting  the 
Mediterranean.  Philippi  informs  us  that  when  he  and  M.  Scacchi  had 
collected  ninety-nine  species  of  them,  he  found  that  only  one,  Pecten 
medius,  now  living  in  the  Red  Sea,  was  absent  from  the  Mediter- 
ranean. Notwithstanding  this,  he  adds,  "the  condition  of  the  sea 
when  the  tufaceous  beds  were  deposited  must  have  been  considerably 
different  from  its  present  state  ;  for  Tellina  striata  was  then  common, 
and  is  now  rare ;  Lucina  spinosa  was  both  more  abundant  and  grew 
to  a  larger  size :  Lucina  fragilis,  now  rare,  and  hardly  measuring 
6  lines,  then  attained  the  enormous  dimensions  of  14  lines,  and 
was  extremely  abundant;  &nd.0strea  lamellosa,  Broc.,  no  longer  met 
with  near  Naples,  existed  at  that  time,  and  attained  a  size  so  large 
that  one  lower  valve  has  been  known  to  measure  5  inches  9  lines 
in  length,  4  inches  in  breadth,  1^  inch  in  thickness,  and  weighed 
26^-  ounces."* 

There  are  other  parts  of  Europe  where  no  volcanic  action  manifests 
itself  at  the  surface,  as  at  Naples,  whether  by  the  eruption  of  lava  or 
}y  earthquakes,  and  yet  where  the  land  and  bed  of  the  adjoining  sea 
.re  undergoing  upheaval.  The  motion  is  so  gradual  as  to  be  insen- 
ble  to  the  inhabitants,  being  only  ascertainable  by  careful  scientific 
leasurements  compared  after  long  intervals.  Such  an  upward  move- 
i^nt  has  been  proved  to  be  in  progress  in  Norway  and  Sweden 
troughout  an  area  about  1000  miles  N.  and  S.,  and  for  an  unknown 
d:tance  E.  and  W.,  the  amount  of  elevation  always  increasing  as  we 
paceed  towards  the  North  Cape,  where  it  may  equal  5  feet  in  a 
eatury.  If  we  could  assume  that  there  had  been  an  average  rise  of 
2^feet  in  each  hundred  years  for  the  last  fifty  centuries,  this  would 
^'Te  an  elevation  of  125  feet  in  that  period.  In  other  words,  it  would 
bllow  that  the  shores,  and  a  considerable  area  of  the  former  bed  of 
'le  Baltic  and  North  Sea,  had  been  uplifted  'vertically  to  that  amount, 
id  converted  into  land  in  the  course  of  the  last  5000  years.  Ac- 
•rdingly,  we  find  near  Stockholm,  in  Sweden,  horizontal  beds  of 
»id,  loam,  and  marl  containing  the  same  peculiar  assemblage  of 
ttacea  which  now  live  in  the  brackish  waters  of  the  Baltic.  Mingled 
Tth  these,  at  different  depths,  have  been  detected  various  works  of 

*  Geol.  Quart.  Journ.  vol.ii.  Memoirs,  p.  15. 
i  4 


120  POST-PLIOCENE   FORMATIONS.  [Cn.  X. 

art  implying  a  rude  state  of  civilization,  and  some  vessels  built  before 
the  introduction  of  iron,  the  whole  marine  formation  having  been 
upraised,  so  that  the  upper  beds  are  now  60  feet  higher  than  the 
surface  of  the  Baltic.  In  the  neighbourhood  of  these  recent  strata, 
both  to  the  north-west  and  south  of  Stockholm,  other  deposits  similar 
in  mineral  composition  occur,  which  ascend  to  greater  heights,  in 
which  precisely  the  same  assemblage  of  fossil  shells  is  met  with,  but 
without  any  intermixture  of  human  bones  or  fabricated  articles. 

On  the  opposite  or  western  coast  of  Sweden,  at  Uddevalla,  post- 
pliocene  strata,  containing  recent  shells,  not  of  that  brackish  water 
character  peculiar  to  the  Baltic,  but  such  as  now  live  in  the  northern 
ocean,  ascend  to  the  height  of  200  feet ;  and  beds  of  clay  and  sand  of 
the  same  age  attain  elevations  of  300  and  even  700  feet  in  Norway, 
where  they  have  been  usually  described  as  "raised  beaches."  They 
are,  however,  thick  deposits  of  submarine  origin,  spreading  far  and 
wide,  and  filling  valleys  in  the  granite  and  gneiss,  just  as  the  tertiary 
formations,  in  different  parts  of  Europe,  cover  or  fill  depressions  in 
the  older  rocks. 

It  is  worthy  of  remark,  that,  although  the  fossil  fauna  charac- 
terizing these  upraised  sands  and  clays  consists  exclusively  of  ex- 
isting northern  species  of  testacea,  yet,  according  to  Loven  (an  able 
living  naturalist  of  Norway),  the  species  do  not  constitute  such  an 
assemblage  as  now  inhabits  corresponding  latitudes  in  the  German 
Ocean.  On  the  contrary,  they  decidedly  represent  a  more  arctic 
fauna.*  In  order  to  find  the  same  species  flourishing  in  equal  abun- 
dance, or  in  many  cases  to  find  them  at  all,  we  must  go  northwards 
to  higher  latitudes  than  Uddevalla  in  Sweden,  or  even  nearer  the 
pole  than  Central  Norway. 

Judging  by  the  uniformity  of  climate  now  prevailing  from  century 
to  century,  and  the  insensible  rate  of  variation  in  the  organic  world 
in  our  own  times,  we  may  presume  that  an  extremely  lengthened 
period  was  required  even  for  so  slight  a  modification  of  the  molluscous 
fauna,  as  that  of  which  the  evidence  is  here  brought  to  light.     O) 
the  other  hand,  we  have  every  reason  for  inferring  on  independer 
grounds  (namely,  the  rate  of  upheaval  of  land  in  modern  times)  th* 
the  antiquity  of  the  deposits  in  question  must  be  very  great.     Forf 
we  assume,  as  before  suggested,  that  the  mean  rate  of  continues 
vertical  elevation  has  amounted  to  2J  feet  in  a  century  (and  this  jsj 
probably  a  high  average),  it  would  require  27,500  years  for  the  s^- 
coast  to  attain  the  height  of  700  feet,  without  making  allowance  br 
any  pauses  such  as  are  now  experienced  in  a  large  part  of  Norway,  or 
for  any  oscillations  of  level. 

In  England,  buried  ships  have  been  found  in  the  ancient  and  no^v 
deserted  channels  of  the  Rother  in  Sussex,  of  the  Mersey  in  Kent 
and  the  Thames  near  London.  Canoes  and  stone  hatchets  have  beei 
dug  up,  in  almost  all  parts  of  the  kingdom,  from  peat  and  shell-marl 
but  there  is  no  evidence,  as  in  Sweden,  Italy,  and  many  other  parf 

*  Quart.  Geol.  Journ.  4  Mems.  p.  48. 


CH,  X.]      RECENT    AND   POST-PLIOCENE   FORMATIONS.  121 

of  the  world,  of  the  bed  of  the  sea,  and  the  adjoining  coast,  having 
been  uplifted  bodily  to  considerable  heights  within  the  human  period. 
Recent  strata  have  been  traced  along  the  coasts  of  Peru  and  Chili, 
inclosing  shells  in  abundance,  all  agreeing  specifically  with  those  now 
swarming  in  the  Pacific.  In  one  bed  of  this  kind,  in  the  island  of 
San  Lorenzo,  near  Lima,  Mr.  Darwin  found,  at  the  altitude  of  85 
feet  above  the  sea,  pieces  of  cotton-thread,  plaited  rush,  and  the 
head  of  a  stalk  of  Indian  corn,  the  whole  of  which  had  evidently 
been  imbedded  with  the  shells.  At  the  same  height  on  the  neigh- 
bouring mainland,  he  found  other  signs  corroborating  the  opinion 
that  the  ancient  bed  of  the  sea  had  there  also  been  uplifted  85  feet 
since  the  region  was  first  peopled  by  the  Peruvian  race.  *  But 
similar  shelly  masses  are  also  met  with  at  much  higher  elevations,  at 
innumerable  points  between  the  Chilian  and  Peruvian  Andes  and 
the  sea-coast,  in  which  no  human  remains  were  ever,  or  in  all  pro- 
bability ever  will  be,  discovered. 

In  the  West  Indies,  also,  in  the  island  of  Guadaloupe,  a  solid  lime- 
stone occurs  at  the  level  of  the  sea-beach,  enveloping  human  skele- 
tons. The  stone  is  extremely  hard,  and  chiefly  composed  of  com- 
minuted shell  and  coral,  with  here  and  there  some  entire  corals  and 
shells,  of  species  now  living  in  the  adjacent  ocean.  With  them  are 
included  arrow-heads,  fragments  of  pottery,  and  other  articles  of 
human  workmanship.  A  limestone  with  similar  contents  has  been 
formed,  and  is  still  forming,  in  St.  Domingo.  But  there  are  also 
more  ancient  rocks  in  the  West  Indian  Archipelago,  as  in  Cuba,  near 
the  Havanna,  and  in  other  islands,  in  which  are  shells  identical  with 
those  now  living  in  corresponding  latitudes ;  some  well-preserved, 
others  in  a  state  of  casts,  all  referable  to  the  ^)ost-pliocene  period. 

I  have  already  described  in  the  seventh  chapter,  p.  84. ,  what  would 
be  the  effect  of  oscillations  and  changes  of  level  in  any  region  drained 
by  a  great  river  and  its  tributaries,  supposing  the  area  to  be  first 
depressed  several  hundred  feet,  and  then  re-elevated.  I  believe  that 
such  changes  in  the  relative  level  of  land  and  sea  have  actually  oc- 
curred in  the  post-pliocene  era  in  the  hydrographical  basin  of  the 
Mississippi  and  in  that  of  the  Rhine.  The  accumulation  of  fluviatile 
matter  in  a  delta  during  a  slow  subsidence  may  raise  the  newly 
gained  land  superficially  at  the  same  rate  at  whjch  its  foundations 
sink,  so  that  these  may  go  down  hundreds  or  thousands  of  feet  per- 
pendicularly, and  yet  the  sea  bordering  the  delta  may  always  be 
excluded,  the  whole  deposit  continuing  to  be  terrestrial  or  freshwater 
in  character.  This  appears  to  have  happened  in  the  deltas  both  of 
the  Po  and  Ganges,  for  recent  artesian  borings,  penetrating  to  the 
depth  of  400  feet,  have  there  shown  that  fluviatile  strata,  with  shells 
of  recent  species,  together  with  ancient  surfaces  of  land  supporting 
turf  and  forests,  are  depressed  hundreds  of  feet  below  the  sea  level,  j" 
Should  these  countries  be  once  more  slowly  upraised,  the  rivers  would 

*  Journal,  p.  451. 

f  See  Principles,  8th  ed.  pp.  260—268.,  9th  ed.  257—280. 


122  LOESS   OF   THE   VALLEY   OF   THE   RHINE,          [Cn.  X. 

carve  out  valleys  through  the  horizontal  and  unconsolidated  strata  as 
they  rose,  sweeping  away  the  greater  portion  of  them,  and  leaving 
mere  fragments  in  the  shape  of  terraces  skirting  newly-formed  allu- 
vial plains,  as  monuments  of  the  former  levels  at  which  the  rivers 
ran.  Of  this  nature  are  "  the  bluffs, "  or  river  cliffs,  now  bounding 
the  valley  of  the  Mississippi  throughout  a  large  portion  of  its 
"course."  The  upper  portions  of  these  bluffs  which  at  Natches  and 
elsewhere  often  rise  to  the  height  of  200  feet  above  the  alluvial  plain, 
consist  of  loam  containing  land  and  freshwater  shells  of  the  genera 
Helix,  Pupa,  Succinea,  and  Lymnea,  of  the  same  species  as  those  now 
inhabiting  the  neighbouring  forests  and  swamps.  In  the  same  loam 
also  are  found  the  bones  of  the  Mastodon,  Elephant,  Megalonyx. 
and  other  extinct  quadrupeds.  * 

I  have  endeavoured  to  show  that  the  deposits  forming  the  delta 
and  alluvial  plain  of  the  Mississippi  consist  of  sedimentary  matter, 
extending  over  an  area  of  30,000  square  miles,  and  known  in  some 
parts  to  be  several  hundred  feet  deep.  Although  we  cannot  estimate 
correctly  how  many  years  it  may  have  required  for  the  river  to  bring 
down  from  the  upper  country  so  large  a  quantity  of  earthy  matter  — 
the  data  for  such  a  computation  being  as  yet  incomplete — we  may 
still  approximate  to  a  minimum  of  the  time  which  such  an  operation 
must  have  taken,  by  ascertaining  experimentally  the  annual  discharge 
of  water  by  the  Mississippi,  and  the  mean  annual  amount  of  solid  matter 
contained  in  its  waters.  The  lowest  estimate  of  the  time  required 
would  lead  us  to  assign  a  high  antiquity,  amounting  to  many  tens  of 
thousands  of  years  to  the  existing  delta,  the  origin  of  which  is  never- 
theless an  event  of  yesterday  when  contrasted  with  the  terraces, 
formed  of  the  loam  above  mentioned.  The  materials  of  the  bluffs 
were  produced  during  the  first  part  of  a  great  oscillation  of  level  which 
depressed  to  a  depth  of  200  feet  a  larger  area  than  the  modern  delta 
and  plain  of  the  Mississippi,  and  then  restored  the  whole  region  to  its 
former  position.f 

Loess  of  the  Valley  of  the  Rhine.  —  A  similar  succession  of  geo- 
graphical changes,  attended  by  the  production  of  a  fluviatile  formation, 
singularly  resembling  that  which  bounds  the  great  plain  of  the 
Mississippi,  seems  to  have  occurred  in  the  hydrographical  basin  of  the 
Rhine,  since  the  time  when  that  basin  had  already  acquired  its  present 
outline  of  hill  and  valley.  I  allude  to  the  deposit  provincially  termed 
loess  in  part  of  Germany,  or  lehm  in  Alsace,  filled  with  land  and 
freshwater  shells  of  existing  species.  It  is  a  finely  comminuted  sand  or 
pulverulent  loam  of  a  yellowish  grey  colour,  consisting  chiefly  of  argil- 
laceous matter  combined  with  a  sixth  part  of  carbonate  of  lime,  and  a 
sixth  of  quartzose  and  micaceous  sand.  It  often  contains  calcareous 
sandy  concretions  or  nodules,  rarely  exceeding  the  size  of  a  man's 
head.  Its  entire  thickness  amounts,  in  some  places,  to  between  200 
and  300  feet ;  yet  there  are  often  no  signs  of  stratification  in  the 

*  See  Principles  of  Geol.  9th  ed.,  and  Lyell's  Second  Visit  to  the  United  States, 
vol.  ii.  p.  257. 

f  Lyell's  Second  Visit  to  the  United  States,  vol.  ii.  chap,  xxxiv. 


CH.  X.J  AND   ITS  FOSSILS.  123 

mass,  except  here  and  there  at  the  bottom,  where  there  is  occasionally  a 
slight  intermixture  of  drifted  materials  derived  from  subjacent  rocks. 
Unsolidified  as  it  is,  and  of  so  perishable  a  nature,  that  every  stream- 
let flowing  over  it  cuts  out  for  itself  a  deep  gully,  it  usually  terminates 
in  a  vertical  cliff,  from  the  surface  of  which  land-shells  are  seen  here 
and  there  to  project  in  relief.  In  all  these  features  it  presents  a 
precise  counterpart  to  the  loess  of  the  Mississippi.  It  is  so  homo- 
geneous as  generally  to  exhibit  no  signs  of  stratification,  owing,  pro- 
bably, to  its  materials  having  been  derived  from  a  common  source, 
and  having  been  accumulated  by  a  uniform  action.  Yet  it  displays 
in  some  few  places  decided  marks  of  successive  deposition,  where 
coarser  and  finer  materials  alternate,  especially  near  the  bottom. 
Calcareous  concretions,  also  enclosing  land-shells,  are  sometimes  ar- 
ranged in  horizontal  layers.  It  is  a  remarkable  deposit,  from  its 
position,  wide  extent,  and  thickness,  its  homogeneous  mineral  com- 
position, and  freshwater  origin.  Its  distribution  clearly  shows  that 
after  the  great  valley  of  the  Rhine,  from  Schaffhausen  to  Bonn,  had 
acquired  its  present  form,  having  its  bottom  strewed  over  with  coarse 
gravel,  a  period  arrived  when  it  became  filled  up  from  side  to  side 
with  fine  mud,  probably  deposited  during  river  inundations ;  and  it  is 
also  clear  tlmt  similar  mud  and  silt  were  thrown  down  contempo- 
raneously in  the  valleys  of  the  principal  tributaries  of  the  Rhine. 

Thus,  for  example,  it  may  be  traced  far  into  Wiirtemberg,  up  the 
valley  of  the  Neckar,  and  from  Frankfort,  up  the  valley  of  the  Main, 
to  above  Dettelbach.  I  have  also  seen  it  spreading  over  the  country  of 
Mayence,  Eppelsheim,  and  Worms,  on  the  left  bank  of  the  Rhine, 
and  on  the  opposite  side  on  the  table-land  above  the  Bergstrasse,  be- 
tween Wiesloch  and  Bruchsal,  where  it  attains'  a  thickness  of  200  feet. 
Near  Strasburg,  large  masses  of  it  appear  at  the  foot  of  the  Yosges 
on  the  left  bank,  and  at  the  base  of  the  mountains  of  the  Black  Forest 
on  the  right  bank.  The  Kaiserstuhl,  a  volcanic  mountain  which 
stands  in  the  middle  of  the  plain  of  the  Rhine  near  Freiburg,  has 
been  covered  almost  everywhere  with  this  loam,  as  have  the  extinct 
volcanos  between  Coblentz  and  Bonn.  Near  Andernach,  in  the 
Kirchweg,  the  loess  containing  the  usual  shells  alternates  with  vol- 
canic matter ;  and  over  the  whole  are  strewed  layers  of  pumice, 
lapilli,  and  volcanic  sand,  from  10  to  15  feet  thick,  very  much  re- 
sembling the  ejections  under  which  Pompeii  lies  buried.  There  is  no 
passage  at  this  upper  junction  from  the  loess  into  the  pumiceous  super- 
stratum ;  and  this  last  follows  the  slope  of  the  hill,  just  as  it  would 
have  done  had  it  fallen  in  showers  from  the  air  on  a  declivity  partly 
formed  of  loess. 

But,  in  general,  the  loess  overlies  all  the  volcanic  products,  even 
those  between  Neuwied  Itid  Bonn,  which  have  the  most  modern 
aspect ;  and  it  has  filled  up  in  part  the  crater  of  the  Roderberg,  an 
extinct  volcano  near  Bonn.  In  1833  a  well  was  sunk  at  the  bottom 
of  this  crater,  through  70  feet  of  loess,  in  part  of  which  were  the 
usual  calcareous  concretions. 

The  interstratification   above  alluded  to  of  loess  with  layers  of 


124      LOESS  OF  THE  VALLEY  OF  THE  RHINE,     [Cn.  X. 

purnice  and  volcanic  ashes,  has  led  to  the  opinion  that  both  during 
and  since  its  deposition  some  of  the  last  volcanic  eruptions  of  the 
Lower  Eifel  have  taken  place.  Should  such  a  conclusion  be  adopted, 
we  should  be  called  upon  to  assign  a  very  modern  date  to  these 
eruptions.  This  curious  point,  therefore,  deserves  to  be  reconsidered ; 
since  it  may  .possibly  have  happened  that  the  waters  of  the  Rhine, 
swollen  by  the  melting  of  snow  and  ice,  and  flowing  at  a  great  height 
through  a  valley  choked  up  with  loess,  may  have  swept  away  the 
loose  superficial  scoriae  and  pumice  of  the  Eifel  volcanos,  and  spread 
them  out  occasionally  over  the  yellow  loam.  Sometimes,  also,  the 
melting  of  snow  on  the  slope  of  small  volcanic  cones  may  have  given 
rise  to  local  floods  capable  of  sweeping  down  light  pumice  into  the 
adjacent  low  grounds. 

The  first  idea  which  has  occurred  to  most  geologists,  after  ex- 
amining the  loess  between  Mayence  and  Basle,  is  to  imagine  that  a 
great  lake  once  extended  throughout  the  valley  of  the  Rhine  between 
those  two  places.  Such  a  lake  may  have  sent  off  large  branches  up 
the  course  of  the  Main,  Neckar,  and  other  tributary  valleys,  in  all  of 
which  large  patches  of  loess  are  now  seen.  The  barrier  of  the 
lake  might  be  placed  somewhere  in  the  narrow  and  picturesque 
gorge  of  the  Rhine  between  Bingen  and  Bonn.  But  this  theory  fails 
altogether  to  explain  the  phenomena ;  when  we  discover  that  that 
gorge  itself  has  once  been  filled  with  loess,  which  must  have  been 
tranquilly  deposited  in  it,  as  also  in  the  lateral  valley  of  the  Lahn, 
communicating  with  the  gorge.  The  loess  has  also  overspread  the 
high  adjoining  platform  near  the  village  of  Plaidt  above  Andernach. 
Nay,  on  proceeding  farther  down  to  the  north,  we  discover  that  the 
hills  which  skirt  the  great  valley  between  Bonn  and  Cologne  have 
loess  on  their  flanks,  which  also  covers  here  and  there  the  gravel  of 
the  plain  as  far  as  Cologne,  and  the  nearest  rising  grounds.  *?/  ' 

Besides  these  objections  to  the  lake  theory,  the  loess  is  met  with 
near  Basle,  capping  hills  more  than  1200  feet  above  the  sea ;  so  that 
a  barrier  of  land  capable  of  separating  the  supposed  lake  from  the 
ocean  would  require  to  be,  at  least,  as  high  as  the  mountains  called 
the  Siebengebirge,  near  Bonn,  the  loftiest  summit  of  which,  the 
Oehlberg,  is  1209  feet  above  the  Rhine  and  1369  feet  above  the  sea. 
It  would  be  necessary,  moreover,  to  place  this  lofty  barrier  some- 
where below  Cologne,  or  precisely  where  the  level  of  the  land  is  now 
lowest. 

Instead,  therefore,  of  supposing  one  continuous  lake  of  sufficient 
extent  and  depth  to  allow  of  the  simultaneous  accumulation  of  the 
loess,  at  various  heights,  throughout  the  whole  area  where  it  now 
occurs,  I  formerly  suggested  that,  subsequently  to  the  period  when 
the  countries  now  drained  by  the  Rhine  and  its  tributaries  had 
nearly  acquired  their  actual  form  and  geographical  features,  they 
were  again  depressed  gradually  by  a  movement  like  that  now  in  pro- 
gress on  the  west  coast  of  Greenland.  *  In  proportion  as  the  whole 

*  Princ.  of  Geol.  3d  edition,  1834,  vol.  iii.  p,  414. 


CH.  X.]  AND   ITS   FOSSILS.  125 

district  was  lowered,  the  general  fall  of  the  waters  between  the  Alps 
and  the  ocean  was  lessened ;  and  both  the  main  and  lateral  valleys, 
becoming  more  subject  to  river  inundations,  were  partially  filled  up 
with  fluviatile  silt,  containing  land  and  freshwater  shells.  When  a 
thickness  of  many  hundred  feet  of  loess  had  been  thrown  down  slowly 
by  this  operation,  the  whole  region  was  once  more  upheaved  gra- 
dually. During  this  upward  movement  most  of  the  fine  loam  would 
be  carried  off  by  the  denuding  power  of  rains  and  rivers  ;  and  thus 
the  original  valleys  might  have  been  re-excavated,  and  the  country 
almost  restored  to  its  pristine  state,  with  the  exception  of  some 
masses  and  patches  of  loess  such  as  still  remain,  and  which,  by  their 
frequency  and  remarkable  homogeneousness  of  composition  and  fos- 
sils, attest  the  ancient  continuity  and  common  origin  of  the  whole. 
By  imagining  these  oscillations  of  level,  we  dispense  with  the  neces- 
sity of  erecting  and  afterwards  removing  a  mountain  barrier  suffi- 
ciently high  to  exclude  the  ocean  from  the  valley  of  the  Rhine  during 
the  period  of  the  accumulation  of  the  loess. 

The  proportion  of  land-shells  of  the  genera  Helix,  Pupa,  and 
Bulimus  is  very  large  in  the  loess ;  but  in  many  places  aquatic  spe- 
cies of  the  genera  Lymnea,  Paludina,  and  Planorbis  are  also  found. 
These  may  have  been  carried  away  during  floods  from  shallow  pools 
and  marshes  bordering  the  river ;  and  the  great  extent  of  marshy 
ground  caused  by  the  wide  overflowings  of  rivers  above  supposed 
would  favour  the  multiplication  of  amphibious  mollusks,  such  as  the 
Succinea  (fig.  106.),  which  is  almost  everywhere  characteristic  of 
this  formation,  and  is  sometimes  accompanied,  as  near  Bonn,  by  an- 
other species,  S.  amphibia  (fig.  34.  p.  29.).  Among  other  abundant 
fossils  are  Helex  plebeium  and  Pupa  muscorum.  (See  Figures.) 


Fig.  106.  Fig.  107. 


4 


Succinea  elongata.  Pupa  muscorum.  Helix  plebeium. 

Both  the  terrestrial  and  aquatic  shells  preserved  in  the  loess  are  of 
most  fragile  and  delicate  structure,  and  yet  they  are  almost  invariably 
perfect  and  uninjured.  They  must  have  been  broken  to  pieces  had 
they  been  swept  along  by  a  violent  inundation.  Even  the  colour  of ' 
some  of  the  land-shells,  as  that  of  Helix  nemoralis,  is  occasionally 
preserved. 

Bones  of  vertebrated  animals  are  rare  in  the  loess,  but  those  of  the 
mammoth,  horse,  and  some  other  quadrupeds  have  been  met  with. 
At  the  village  of  Binningen,  and  the  hills  called  Bruder  Holz,  near 
Basle,  I  found  the  vertebrae  of  fish,  together  with  the  usual  shells. 
These  vertebrae,  according  to  M.  Agassiz,  belong  decidedly  to  the 
Shark  family,  perhaps  to  the  genus  Lamna.  In  explanation  of  their 
occurrence  among  land  and  freshwater  shells,  it  may  be  stated  that 
certain  fish  of  this  family  ascend  the  Senegal,  Amazon,  and  other 


126  BOULDER   FORMATION.  [Cn.  XI. 

great  rivers,  to  the  distance  of  several  hundred  miles  from  the 
ocean.* 

At  Cannstadt,  near  Stuttgardt,  in  a  valley  also  belonging  to  the 
hydrographical  basin  of  the  Rhine,  I  have  seen  the  loess  pass  down- 
wards into  beds  of  calcareous  tuff  and  travertin.  Several  valleys  in 
northern  Germany,  as  that  of  the  Ilm  at  Weimar,  and  that  of  the 
Tonna,  north  of  Gotha,  exhibit  similar  masses  of  modern  limestone 
filled  with  recent  shells  of  the  genera  Planorbis,  Lymnea^  Paludina, 
&c.,  from  50  to  80  feet  thick,  with  a  bed  of  loess  much  resembling 
that  of  the  Rhine,  occasionally  incumbent  on  them.  In  these  modern 
limestones  used  for  building,  the  bones  of  Elephas  primigenius,  Rhi- 
noceros tichorhinus,  Ursus  spelceus,  Hycena  spelcea,  with  the  horse,  ox, 
deer,  and  other  quadrupeds,  occur;  and  in  1850  Mr.  H.  Credner  and 
I  obtained  in  a  quarry  at  Tonna,  at  the  depth  of  15  feet,  inclosed  in 
the  calcareous  rock  and  surrounded  with  dicotyledonous  leaves  and 
petrified  leaves,  four  eggs  of  a  snake  of  the  size  of  the  largest  Euro- 
pean Coluber,  which,  with  three  others,  were  lying  in  a  series,  or 
string. 

They  are,  I  believe,  the  first  reptilian  remains  which  have  been 
met  with  in  strata  of  this  age. 

The  agreement  of  the  shells  in  these  cases  with  recent  European 
species  enables  us  to  refer  to  a  very  modern  period  the  filling  up 
and  re-excavation  of  the  valleys ;  an  operation  which  doubtless  con- 
sumed a  long  period  of  time,  since  which  the  mammiferous  fauna  has 
undergone  a  considerable  change. 


CHAPTER  XI. 

NEWER   PLIOCENE   PERIOD.  —  BOULDER   FORMATION. 

Drift  of  Scandinavia,  northern  Germany,  andEussia — Its  northern  origin  —  Not  all 
of  the  same  age  —  Fundamental  rocks  polished,  grooved,  and  scratched  —  Action 
of  glaciers  and  icebergs — Fossil  shells  of  glacial  period — Drift  of  eastern  Nor- 
folk —  Associated  freshwater  deposit  — Bent  and  folded  strata  lying  on  undisturbed 
beds — Shells  on  Moel  Tryfane  —  Ancient  glaciers  of  North  Wales  —  Irish  drift. 

AMONG  the  different  kinds  of  alluvium  described  in  the  seventh  chapter, 
mention  was  made  of  the  boulder  formation  in  the  north  of  Europe, 
the  peculiar  characters  of  which  may  now  be  considered,  as  it  belongs 
in  part  to  the  post-pliocene,  and  partly  to  the  newer  pliocene,  period. 
I  shall  first  allude  briefly  to  that  portion  of  it  which  extends  from 
Finland  and  the  Scandinavian  mountains  to  the  north  of  Russia,  and 
the  low  countries  bordering  the  Baltic,  and  which  has  been  traced 
southwards  as  far  as  the  eastern  coast  of  England.  This  formation 

*  Proceedings  Geol.  Soc.  No.  43.  p.  222. 


CH.  XL]  ROCKS  DRIFTED   BY   ICE.  127 

consists  of  mud,  sand,  and  clay,  sometimes  stratified,  but  often  wholly 
devoid  of  stratification,  for  a  depth  of  more  than  a  hundred  feet. 
To  this  unstratified  form  of  the  deposit,  the  name  of  till  has  been 
applied  in  Scotland.  It  generally  contains  numerous  fragments  of 
rocks,  some  angular  and  others  rounded,  which  have  been  derived 
from  formations  of  all  ages,  both  fossiliferous,  volcanic,  and  hypo- 
gene,  and  which  have  often  been  brought  from  great  distances.  Some 
of  the  travelled  blocks  are  of  enormous  size,  several  feet  or  yards  in 
diameter  ;  their  average  dimensions  increasing  as  we  advance  north- 
wards. The  till  is  almost  everywhere  devoid  of  organic  remains, 
unless  where  these  have  been  washed  into  it  from  older  formations ; 
so  that  it  is  chiefly  from  relative  position  that  we  must  hope  to  derive 
a  knowledge  of  its  age. 

Although  a  large  proportion  of  the  boulder  deposit,  or  "  northern 
drift,"  as  it  has  sometimes  been  called,  is  made  up  o^  fragments 
brought  from  a  distance,  and  which  have  sometimes  travelled  many 
hundred  miles,  the  bulk  of  the  mass  in  each  locality  consists  of  the 
ruins  of  subjacent  or  neighbouring  rocks  ;  so  that  it  is  red  in  a  region 
of  red  sandstone,  white  in  a  chalk  country,  and  grey  or  black  in  a 
district  of  coal  and  coal-shale. 

The  fundamental  rock  on  which  the  boulder  formation  reposes,  if 
it  consists  of  granite,  gneiss,  marble,  or  other  hard  stone  capable  of 
permanently  retaining  any  superficial  markings  which  may  have 
been  imprinted  upon  it,  is  usually  smoothed  or  polished,  and  exhibits 
parallel  strise  and  furrows  having  a  determinate  direction.  This 
direction,  both  in  Europe  and  North  America,  is  evidently  connected 
with  the  course  taken  by  the  erratic  blocks  in  the  same  district,  being 
from  north  to  south,  or  if  it  be  20  or  30  degrees  to  the  east  or  west  of 
north,  always  corresponding  to  the  direction  in  which  the  large  an- 
gular and  rounded  stones  have  travelled.  These  stones  themselves 
also  are  often  furrowed  and  scratched  on  more  than  one  side. 

In  explanation  of  such  phenomena  I  may  refer  the  student  to  what 
was  said  of  the  action  of  glaciers  and  icebergs  in  the  Principles  of 
Geology,  (ch.  xv.)  It  is  ascertained  that  hard  stones,  frozen  into 
a  moving  mass  of  ice,  and  pushed  along  under  the  pressure  of  that 
mass,  scoop  out  long  rectilinear  furrows  or  grooves  parallel  to  each 
other  on  the^eubjacent  solid  rock.  (See  fig.  109.)  Smaller  scratches 
and  strise  are  made  on  the  polished  surface  by  crystals  or  projecting 
edges  of  the  hardest  minerals,  just  as  a  diamond  cuts  glass.  The 
recent  polishing  and  striation  of  limestone  by  coast-ice  carrying 
boulders  even  as  far  south  as  the  coast  of  Denmark,  has  been  ob- 
served by  Dr.  Forchhammer,  and  helps  us  to  conceive  how  large  ice- 
bergs, running  aground  on  the  bed  of  the  sea,  may  produce  similar 
furrows  on  a  grander  scale.  An  account  was  given  so  long  ago  as 
the  year  1822,  by  Scoresby,  of  icebergs  seen  by  him  drifting  along 
in  latitudes  69°  and  70°  N.,  which  rose  above  the  surface  from  100  to 
200  feet,  and  measured  from  a  few  yards  to  a  mile  in  circumference. 
Many  of  them  were  loaded  with  beds  of  earth  and  rock,  of  such  thick- 
ness that  the  weight  was  conjectured  to  be  from  50,000  to  100,000 


128  HOCKS  DRIFTED  BY  ICE.  [Cu.  XI. 

Fig.  109. 


Limestone  polished,  furrowed,  and  scratched  by  the  glacier  of  Rosenlaui,  in  Switzerland.  (Agassiz.) 
a  a.  White  streaks  or  scratches,  caused  by  small  grains  of  flint  frozen  into  the  ice. 
b  b.  Furrows. 

tons.  A  similar  transportation  of  rocks  is  known  to  be  in  progress 
in  the  southern  hemisphere,  where  boulders  included  in  ice  are  far 
more  frequent  than  in  the  north.  One  of  these  icebergs  was  en- 
countered in  1839,  in  mid-ocean,  in  the  antarctic  regions,  many 
hundred  miles  from  any  known  land,  sailing  northwards,  with  a 
large  erratic  block  firmly  frozen  into  it.  In  order  to  understand  in 
what  manner  long  and  straight  grooves  may  be  cut  by  such  agency, 
we  must  remember  that  these  floating  islands  of  ice  have  a  singular 
steadiness  of  motion,  in  consequence  of  the  larger  portion  of  their 
bulk  being  sunk  deep  under  water,  so  that  they  are  not  perceptibly 
moved  by  the  winds  and  waves  even  in  the  strongest  gales.  Many 
had  supposed  that  the  magnitude  commonly  attributed  to  icebergs 
by  unscientific  navigators  was  exaggerated,  but  now  it  appears  that 
the  popular  estimate  of  their  dimensions  has  rather  fallen  within 
than  beyond  the  truth.  Many  of  them,  carefully  measured  by  the 
officers  of  the  French  exploring  expedition  of  the  Astrolabe,  were 
between  100  and  225  feet  high  above  water,  and  from  2  to  5  miles 
in  length.  Captain  d'Urville  ascertained  one  of  them  which  he  saw 
floating  in  the  Southern  Ocean  to  be  13  miles  long  and  100  feet  high, 
with  walls  perfectly  vertical.  The  submerged  portions  of  such  islands 
must,  according  to  the  weight  of  ice  relatively  to  sea-water,  be  from 
six  to  eight  times  more  considerable  than  the  part  which  is  visible, 
so  that  the  mechanical  power  they  might  exert  when  fairly  set  in 
motion  must  be  prodigious.  *  A  large  proportion  of  these  floating 
masses  of  ice  are  supposed  not  to  be  derived  from  terrestrial  glaciers 

*  T.  L.  Hayes,  Boston  Journ.  Nat.  Hist.  1844. 


CH.  XL]  ORIGIN   OF   TILL.  129 

(Principles,  ch.  xv.),  but  to  be  formed  at  the  foot  of  cliffs  by  the 
drifting  of  snow  from  the  land  over  the  frozen  surface  of  the  sea. 

We  know  that  in  Switzerland,  when  glaciers  laden  with  mud  and 
stones  melt  away  at  their  lower  extremity  before  reaching  the  sea, 
they  leave  wherever  they  terminate  a  confused  heap  of  unstratified 
rubbish,  called  "  a  moraine,"  composed  of  mud,  sand,  and  pieces  of  all 
the  rocks  with  which  they  were  loaded.  We  may  expect,  therefore, 
to  find  a  formation  of  the  same  kind,  resulting  from  the  liquefaction 
of  icebergs,  in  tranquil  water.  But,  should  the  action  of  a  current 
intervene  at  certain  points  or  at  certain  seasons,  then  the  materials 
will  be  sorted  as  they  fall,  and  arranged  in  layers  according  to  their 
relative  weight  and  size.  Hence  there  will  be  passages  from  till,  as 
it  is  called  in  Scotland,  to  stratified  clay,  gravel,  and  sand,  and  inter- 
calations of  one  in  the  other. 

I  have  yet  to  mention  another  appearance  connected  with  the 
boulder  formation,  which  has  justly  attracted  much  attention  in 
Norway  and  other  parts  of  Europe.  Abrupt  pinnacles  and  out- 
standing ridges  of  rock  are  often  observed  to  be  polished  and  furrowed 
on  the  north  side,  or  on  the  side  facing  the  region  from  which  the 
erratics  have  come  ;  while  on  the  other,  which  is  usually  steeper  and 
often  perpendicular,  called  the  "  lee-side,"  such  superficial  markings 
are  wanting.  There  is  usually  a  collection  on  this  lee-side  of 
boulders  and  gravel,  or  of  large  angular  fragments.  In  explanation 
we  may  suppose  that  the  north  side  was  exposed,  when  still  sub- 
merged, to  the  action  of  icebergs,  and  afterwards,  when  the  land  was 
upheaved,  of  coast  ice,  which  ran  aground  upon  shoals,  or  was  packed 
on  the  beach ;  so  that  there  would  be  great  wear  and  tear  on  the 
seaward  slope,  while,  on  the  other,  gravel  and  boulders  might  be 
heaped  up  in  a  sheltered  position. 

Northern  origin  of  erratics. — That  the  erratics  of  northern  Europe 
have  been  carried  southward  cannot  be  doubted ;  those  of  granite, 
for  example,  scattered  over  large  districts  of  Russia  and  Poland, 
agree  precisely  in  character  with  rocks  of  the  mountains  of  Lapland 
and  Finland ;  while  the  masses  of  gneiss,  syenite,  porphyry,  and  trap, 
strewed  over  the  low  sandy  countries  of  Pomerania,  Holstein,  and 
Denmark,  are  identical  in  mineral  characters  with  the  mountains  of 
Norway  and  Sweden. 

It  is  found  to  be  a  general  rule  in  Russia,  that  the  smaller  blocks ' 
are  carried  to  greater  distances  from  their  point  of  departure  than 
the  larger ;  the  distance  being  sometimes  800  and  even  1000  miles 
from  the  nearest  rocks  from  which  they  were  broken  off;  the  direc- 
tion having  been  from  N.W.  to  S.E.,  or  from  the  Scandinavian 
mountains  over  the  seas  and  low  lands  to  the  south-east.  That  its 
accumulation  throughout  this  area  took  place  in  part  during  the  post- 
pliocene  period  is  proved  by  its  superposition  at  several  points  to 
strata  containing  recent  shells.  Thus,  for  example,  in  European 
Russia,  MM.  Murchison  and  De  Verneuil  found  in  1840,  that  the 
flat  country  between  St.  Petersburg  and  Archangel,  for  a  distance 
of  600  miles,  consisted  of  horizontal  strata,  full  of  shells  similar  to 

K 


130  STRATA   CONTAINING   RECENT    SHELLS.          [Cfl.  XI. 

those  now  inhabiting  the  arctic  sea,  on  which  rested  the  boulder 
formation,  containing  large  erratics. 

In  Sweden,  in  the  immediate  neighbourhood  of  Upsala,  I  had  ob- 
served, in  1834,  a  ridge  of  stratified  sand  and  gravel,  in  the  midst  of 
which  occurs  a  layer  of  marl,  evidently  formed  originally  at  the 
bottom  of  the  Baltic,  by  the  slow  growth  of  the  mussel,  cockle,  and 
other  marine  shells  of  living  species  intermixed  with  some  proper  to 
fresh  water.  The  marine  shells  are  all  of  dwarfish  size,  like  those 
now  inhabiting  the  brackish  waters  of  the  Baltic  ;  and  the  marl,  in 
which  myriads  of  them  are  imbedded,  is  now  raised  more  than  100 
feet  above  the  level  of  the  Gulf  of  Bothnia.  Upon  the  top  of  this 
ridge  repose  several  huge  erratics,  consisting  of  gneiss  for  the  most 
part  unrounded,  from  9  to  16  feet  in  diameter,  and  which  must  have 
been  brought  into  their  present  position  since  the  time  when  the 
neighbouring  gulf  was  already  characterized  by  its  peculiar  fauna.* 
Here,  therefore,  we  have  proof  that  the  transport  of  erratics  continued 
to  take  place,  not  merely  when  the  sea  was  inhabited  by  the  existing 
testacea,  but  when  the  north  of  Europe  had  already  assumed  that 
remarkable  feature  of  its  physical  geography,  which  separates  the 
Baltic  from  the  North  Sea,  and  causes  the  Gulf  of  Bothnia  to  have 
only  one  fourth  of  the  saltness  belonging  to  the  ocean.  In  Denmark, 
also,  recent  shells  have  been  found  in  stratified  beds,  closely  associ- 
ated with  the  boulder  clay. 

It  was  stated  that  in  Russia  the  erratics  diminished  generally  in  size 
in  proportion  as  they  are  traced  farther  from  their  source.  The 
same  observation  holds  true  in  regard  to  the  average  bulk  of  the 
Scandinavian  boulders,  when  we  pursue  them  southwards,  from  the 
south  of  Norway  and  Sweden  through  Denmark  and  Westphalia. 
This  phenomenon  is  in  perfect  harmony  with  the  theory  of  ice-islands 
floating  in  a  sea  of  variable  depth ;  for  the  heavier  erratics  require 
icebergs  of  a  larger  size  to  buoy  them  up ;  and,  even  when  there  are 
no  stones  frozen  in,  more  than  seven  eighths,  and  often  nine  tenths, 
of  a  mass  of  drift  ice  is  under  water.  The  greater,  therefore,  the 
volume  of  the  iceberg,  the  sooner  would  it  impinge  on  some  shallower 
part  of  the  sea ;  while  the  smaller  and  lighter  floes,  laden  with  finer 
mud  and  gravel,  may  pass  freely  over  the  same  banks,  and  be  carried 
to  much  greater  distances.  In  those  places,  also,  where  in  the  course 
*of  centuries  blocks  have  been  carried  southwards  by  coast-ice,  having 
been  often  stranded  and  again  set  afloat  in  the  direction  of  a  pre- 
vailing current,  the  blocks  will  diminish  in  size  the  farther  they 
travel  from  their  point  of  departure  for  two  reasons :  first, 
because  they  will  be  repeatedly  exposed  to  wear  and  tear  by  the 
action  of  the  waves ;  secondly,  because  the  largest  blocks  are  seldom 
without  divisional  planes  or  "joints,"  which  cause  them  to  split  when 
weathered.  Hence,  as  often  as  they  start  on  a  fresh  voyage,  becom- 
ing buoyant  by  coast-ice  which  has  frozen  on  to  them,  one  portion  of 
the  mass  IB  detached  from  the  rest.  A  recent  examination  (in  1852) 

*  See  paper  by  the  author,  Phil.  Trans.  1835,  p.  15. 


CH.  XI.] 


NORTHERN    DRIFT. 


131 


of  several  trains  of  huge  erratics  in  lat.  42°  50'  N.  in  the  United 
States,  in  Berkshire,  on  the  western  confines  of  Massachusetts,  has 
convinced  me  that  this  cause  has  been  very  influential  both  in  re- 
ducing the  size  of  erratics,  and  in  restoring  angularity  to  blocks 
which  would  otherwise  be  rounded  in  proportion  to  their  distance 
from  their  original  starting  point. 

The  "  northern  drift "  of  the  most  southern  latitudes  is  usually  of 
the  highest  antiquity.  In  Scotland  it  rests  immediately  on  the  older 
rocks,  and  is  covered  by  stratified  sand  and  clay,  usually  devoid  of 
fossils,  but  in  which,  at  certain  points  near  the  east  and  west  coast, 
as,  for  example,  in  the  estuaries  of  the  Tay  and  Clyde,  marine  shells 
have  been  discovered.  The  same  shells  have  also  been  met  with  in 
the  north,  at  Wick  in  Caithness,  and  on  the  shores  of  the  Moray 
Frith.  The  principal  deposit  on  the  Clyde  occurs  at  the  height  of 
about  70  feet,  but  a  few  shells  have  been  traced  in  it  as  high  as 


Fig.  110. 
Astarte  borealis. 


Fig.  111. 
Leda  oblonga. 


Fig.  112. 
Saxicava  rugosa. 


Fig.  113. 
Pecten  tslandicus. 


Fig.  114.  Fig.  115. 

Natica  clausa.    Trophon  clathratum. 


Northern  shells  common  in  the  drift  of  the  Clyde,-in  Scotland. 

554  feet  above  the  sea.  Although  a  proportion  of  between  85  or  90 
in  100  of  the  imbedded  shells  are  of  recent  species,  the  remainder 
are  unknown;  and  even  many  which  are  recent  now  inhabit  more 
northern  seas,  where  we  may,  perhaps,  hereafter  find  living  repre- 
sentatives of  some  of  the  unknown  fossils.  The  distance  to  which 
erratic  blocks  have  been  carried  southwards  in  Scotland,  and  the 
course  they  have  taken,  which  is  often  wholly  independent  of  the 
present  position  of  hill  and  valley,  favours  the  idea  that  ice-rafts 
rather  than  glaciers  were  in  general  the  transporting  agents.  The 
Grampians  in  Forfarshire  and  in  Perthshire  are  from  3000  to  4000 
feet  high.  To  the  southward  lies  the  broad  and  deep  valley  of 
Strathmore,  and  to  the  south  of  this  again  rise  the  Sidlaw  Hills  *  to 
the  height  of  1500  feet  and  upwards.  On  the  highest  summits  of 
this  chain,  formed  of  sandstone  and  shale,  and  at  various  elevations, 
are  found  huge  angular  fragments  of  mica-schist,  some  3  and  others 
15  feet  in  diameter,  which  have  been  conveyed  for  a  distance  of  at 
least  15  miles  from  the  nearest  Grampian  rocks  from  which  they 
could  have  been  detached.  Others  have  been  left  strewed  over  the 
bottom  of  the  large  intervening  vale  of  Strathmore. 


*  See  above,  section,  p.  48. 
K  2 


132  NORFOLK  DRIFT   AND  [Cn.  XI. 

Still  farther  south  on  the  Pentland  Hills,  at  the  height  of  1100  feet 
above  the  sea,  Mr.  Maclaren  has  observed  a  fragment  of  mica-schist 
weighing  from  8  to  10  tons,  the  nearest  mountain  composed  of  this 
formation  being  50  miles  distant.* 

The  testaceous  fauna  of  the  boulder  period,  in  Scotland,  England, 
and  Ireland,  has  been  shown  by  Prof.  E.  Forbes  to  contain  a  much 
smaller  number  of  species  than  that  now  belonging  to  the  British 
seas,  and  to  have  been  also  much  less  rich  in  species  than  the  Older 
Pliocene  fauna  of  the  crag  which  preceded  it.  Yet  the  species  are 
nearly  all  of  them  now  living  either  in  the  British  or  more  northern 
seas,  the  shells  of  more  arctic  latitudes  being  the  most  abundant  and 
the  most  wide  spread  throughout  the  entire  area  of  the  drift  from 
north  to  south. 

This  extensive  range  of  the  fossils  can  by  no  means  be  explained 
by  imagining  the  mollusca  of  the  drift  to  have  been  inhabitants  of  a 
deep  sea,  where  a  more  uniform  temperature  prevailed.  On  the  con- 
trary, many  species  were  littoral,  and  others  belonged  to  a  shallow 
sea,  not  above  100  feet  deep,  and  very  few  of  them  lived,  according 
to  Prof.  E.  Forbes,  at  greater  depths  than  300  feet. 

From  what  was  before  stated  it  will  appear  that  the  boulder  forma- 
tion displays  almost  everywhere,  in  its  mineral  ingredients,  a  strange 
heterogeneous  mixture  of  the  ruins  of  adjacent  lands,  with  stones  both 
angular  and  rounded,  which  have  come  from  points  often  very  re- 
mote. Thus  we  find  it  in  our  eastern  counties,  as  in  Norfolk,  Suffolk, 
Cambridge,  Huntingdon,  Bedford,  Hertford,  Essex,  and  Middlesex, 
containing  stones  from  the  Silurian  and  Carboniferous  strata,  and 
from  the  lias,  oolite,  and  chalk,  all  with  their  peculiar  fossils,  together 
with  trap,  syenite,  mica-schist,  granite,  and  other  crystalline  rocks. 
A  fine  example  of  this  singular  mixture  extends  to  the  very  suburbs 
of  London,  being  seen  on  the  summit  of  Muswell  Hill,  Highgate. 
But  south  of  London  the  northern  drift  is  wanting,  as,  for  example, 
in  the  Wealds  of  Surrey,  Kent,  and  Sussex. 

Norfolk  drift.  —  The  drift  can  nowhere  be  studied  more  advan- 
tageously in  England  than  in  the  cliffs  of  the  Norfolk  coast  between 
Happisburgh  and  Cromer.  Vertical  sections,  having  an  ordinary 
height  of  from  50  to  70  feet,  are  there  exposed  to  view  for  a  distance 
of  about  20  miles.  The  name  of  diluvium  was  formerly  given  to  it 
by  those  who  supposed  it  to  have  been  produced  by  the  violent  action 
of  a  sudden  and  transient  deluge,  but  the  term  drift  has  been  sub- 
stituted by  those  who  reject  this  hypothesis.  Here,  as  elsewhere,  it 
consists  for  the  most  part  of  clay,  loam,  and  sand,  in  part  stratified, 
in  part  devoid  of  stratification.  Pebbles,  together  with  some  large 
boulders  of  granite,  porphyry,  greenstone,  lias,  chalk,  and  other 
transported  rocks,  are  interspersed,  especially  through  the  till.  That 
some  of  the  granitic  and  other  fragments  came  from  Scandinavia  I 
have  no  doubt,  after  having  myself  traced  the  course  of  the  conti- 
nuous stream  of  blocks  from  Norway  and  Sweden  to  Denmark,  and 

*  Geol.  of  Fife,  &c.,  p.  220. 


CH.  XI.] 


ASSOCIATED   FRESHWATER    STRATA. 


133 


across  the  Elbe,  through  Westphalia,  to  the  borders  of  Holland.  We 
need  not  be  surprised  to  find  them  reappear  on  our  eastern  coast 
between  the  Tweed  and  the  Thames,  regions  not  half  so  remote 
from  parts  of  Norway  as  are  many  Russian  erratics  from  the  sources 
whence  they  came. 

White  chalk  rubble,  unmixed  with  foreign  matter,  and  even  huge 
fragments  of  solid  chalk,  also  occur  in  many  localities  in  these  Norfolk 
cliffs.  No  fossils  have  been  detected  in  this  drift  which  can  posi- 
tively be  referred  to  the  era  of  its  accumulation  ;  but  at  some  points 
it  overlies  a  freshwater  formation  containing  recent  shells,  and  at 
others  it  is  blended  with  the  same  in  such  a  manner  as  to  force  us  to 
conclude  that  both  were  contemporaneously  deposited. 


Fig.  116. 


Grav 


The  shaded  portion  consists  of  Freshwater  beds. 
Intercalation  of  freshwater  beds  and  of  boulder  clay  and  sand  at  Mundesley. 

This  interstratification  is  expressed  in  the  annexed  figure,  the  dark 
mass  indicating  the  position  of  the  freshwater  beds,  which  contain 
much  vegetable  matter,  and  are  divided  into  thin  layers.  The  im- 
bedded shells  belong  to  the  genera  Planorbis,  Lymnea,  Paludina^ 
Unio,  Cyclas,  and  others,  all  of  British  species,  except  a  minute  Pa- 
ludina  now  inhabiting  France.  (See  fig.  117.) 

Fig.  117. 


Paludina  marginals,  Michaud.    (P.  minuta,  Strickland.) 
The  middle  figure  is  of  the  natural  size. 

The  Cyclas  (fig.  118.)  is  merely  a  remarkable  variety  of  the  com- 
mon English  species.  The  scales  and  teeth  of  fish  of  the  genera 
Pike,  Perch,  Roach,  and  others,  accompany  these  shells;  but  the 

Fig.  118. 


Cyclas  (Pisidium)  amnica,  var.  ? 
The  two  middle  figures  are  of  the  natural  size. 

K   3 


134 


BENT    AND   FOLDED    STRATA. 


[CH.  XI. 


species  are  not  considered  by  M.  Agassiz  to  be  identical  with  known 
British  or  European  kinds. 

The  series  of  formations  in  the  cliffs  of  eastern  Norfolk,  now  under 
consideration,  beginning  with  the  lowest,  is  as  follows  :  —  First, 
chalk ;  secondly,  patches  of  a  marine  tertiary  formation,  called  the 
Norwich  Crag,  hereafter  to  be  described ;  thirdly,  the  freshwater 
beds  already  mentioned ;  and  lastly,  the  drift.  Imme'diately  above 
the  chalk,  or  crag,  when  that  is  present,  is  found  here  and  there  a 
buried  forest,  or  a  stratum  in  which  the  stools  and  roots  of  trees  stand 
in  their  natural  position,  the  trunks  having  been  broken  short  off  and 
imbedded  with  their  branches  and  leaves.  It  is  very  remarkable 
that  the  strata  of  the  overlying  boulder  formation  have  often  under- 
gone great  derangement  at  points  where  the  subjacent  forest  bed  and 
chalk  remain  undisturbed.  There  are  also  cases  where  the  upper 
portion  of  the  boulder  deposit  has  been  greatly  deranged,  while  the 
lower  beds  of  the  same  have  continued  horizontal.  Thus  the  an- 
nexed section  (fig.  119.)  represents  a  cliff  about  50  feet  high,  at  the 


Fig.  119. 


Gravel 


Sand 


Loam 


Till 


Cliff  50  feet  high  between  Bacton  Gap  and  Mundes'Iey. 


bottom  of  which  is  till,  or  unstratified  clay,  containing  boulders, 
having  an  even  horizontal  surface,  on  which  repose  conformably  beds 
of  laminated  clay  and  sand  about  5  feet  thick,  which,  in  their  turn, 
are  succeeded  by  vertical,  bent,  and  contorted  layers  of  sand  and  loam 
20  feet  thick,  the  whole  being  covered  by  flint  gravel.  Now  the 
curves  of  the  variously  coloured  beds  of  loose  sand,  loam,  and  pebbles 
are  so  complicated  that  not  only  may  we  sometimes  find  portions  of 

Fig.  121. 


Fig.  120. 


Folding  of  the  strata  between  East 
and  West  Runton. 


Section  of  concentric  beds  west  of  Cromer. 

1.  Blue  clay.  3.  Yellow  sand. 

2.  White  sand.  4.  Striped  loam  and  clay. 

5.  Laminated  blue  clay. 


CH.  XL]  MASSES   OF   CHALK   IN   DRIFT.  135 

them  which  maintain  their  vertically  to  a  height  of  10  or  15  feet, 
but  they  have  also  been  folded  upon  themselves  in  such  a  manner 
that  continuous  layers  might  be  thrice  pierced  in  one  perpendicular 
boring. 

At  some  points  there  is  an  apparent  folding  of  the  beds  round  a 
central  nucleus,  as  at  a,  fig.  120.,  where  the  strata  seem  bent  round 
a  small  mass  of  chalk ;  or,  as  in  fig.  121.,  where  the  blue  clay,  No.  1., 
is  in  the  centre ;  and  where  the  other  strata,  2,  3,  4,  5,  are  coiled 
round  it;  the  entire  mass  being  20  feet  in  perpendicular  height. 
This  appearance  of  concentric  arrangement  around  a  nucleus  is, 
nevertheless,  delusive,  being  produced  by  the  intersection  of  beds 
bent  into  a  convex  shape  ;  and  that  which  seems  the  nucleus  being,  in 
fact,  the  innermost  bed  of  the  series,  which  has  become  partially 
visible  by  the  removal  of  the  protuberant  portions  of  the  outer  layers. 

To  the  north  of  Cromer  are  other  fine  illustrations  of  contorted 
drift  reposing  on  a  floor  of  chalk  horizontally  stratified  and  having 
a  level  surface.  These  phenomena,  in  themselves  sufficiently  difficult 
of  explanation,  are  rendered  still  more  anomalous  by  the  occasional 
inclosure  in  the  drift  of  huge  fragments  of  chalk  many  yards  in  dia- 
meter. One  striking  instance  occurs  west  of  Sherringham,  where 
an  enormous  pinnacle  of  chalk,  between  70  and  80  feet  in  height,  is 
flanked  on  both  sides  by  vertical  layers  of  loam,  clay,  and  gravel. 
(Fig.  122.) 

Fig.  122. 


Till 


Included  pinnacle  of  chalk  at  Old  Hythe  point,  west  of  Sherringham. 
d.  Chalk  with  regular  layers  of  chalk  flints. 

c.  Layer  called  "  the  pan,"  of  loose  chalk,  flints,  and  marine  shells  of  recent 
species,  cemented  by  oxide  of  iron. 

This  chalky  fragment  is  only  one  of  many  detached  masses  which 

ve  been  included  in  the  drift,  and  forced  along  with  it  into  their 

present  position.     The  level  surface  of  the  chalk  in  situ  (d)  may  be 

traced  for  miles  along  the  coast,  where  it  has  escaped  the  violent 

movements  to  which  the  incumbent  drift  has  been  exposed.* 

I 

*  For  a  full  account  of  the  drift  of  East  Norfolk,  see  a  paper  by  the  author,  Phil. 
Mag.  No.  104.  May,  1840. 

K  4 


136  ICE-ISLANDS.  [Cn.  XI. 

We  are  called  upon,  then,  to  explain  how  any  force  can  have  been 
exerted  against  the  upper  masses,  so  as  to  produce  movements  in 
which  the  subjacent  strata  have  not  participated.  It  may  be  an- 
swered that,  if  we  conceive  the  till  and  its  boulders  to  have  been 
drifted  to  their  present  place  by  ice,  the  lateral  pressure  may  have 
been  supplied  by  the  stranding  of  ice-islands.  We  learn,  from  the  ob- 
servations of  Messrs.  Dease  and  Simpson  in  the  polar  regions,  that 
such  islands,  when  they  run  aground,  push  before  them  large  mounds  ot 
shingle  and  sand.  It  is  therefore  probable  that  they  often  cause  great 
alterations  in  the  arrangement  of  pliant  and  incoherent  strata  forming 
the  upper  part  of  shoals  or  submerged  banks,  the  inferior  portions  of 
the  same  remaining  unmoved.  Or  many  of  the  complicated  curva- 
tures of  these  layers  of  loose  sand  and  gravel  may  have  been  due  to 
another  cause,  the  melting  on  the  spot  of  icebergs  and  coast  ice  in 
which  successive  deposits  of  pebbles,  sand,  ice,  snow,  and  mud,  to- 
gether with  huge  masses  of  rock  fallen  from  cliifs,  may  have  become 
interstratified.  Ice-islands  so  constituted  often  capsize  when  afloat, 
and  gravel  once  horizontal  may  have  assumed,  before  the  associated 
ice  was  melted,  an  inclined  or  vertical  position.  The  packing  of  ice 
forced  up  on  a  coast  may  lead  to  similar  derangement  in  a  frozen 
conglomerate  of  sand  or  shingle,  and,  as  Mr.  Trimmer  has  suggested*, 
alternate  layers  of  earthy  matter  may  have  sunk  down  slowly  during 
the  liquefaction  of  the  intercalated  ice,  so  as  to  assume  the  most  fan- 
tastic and  anomalous  positions,  while  the  strata  below,  and  those 
afterwards  thrown  down  above,  may  be  perfectly  horizontal. 

There  is,  however,  still  another  mode  in  which  some  of  these 
bendings  may  have  been  produced.  When  a  railway  embankment  is 
thrown  across  a  marsh  or  across  the  bed  of  a  drained  lake,  we  fre- 
quently find  that  the  foundation,  consisting  of  peat  and  shell-marl,  or 
of  quicksand  and  mud,  gives  way,  and  sinks  as  fast  as  the  embank- 
ment is  raised  at  the  top.  At  the  same  time,  there  is  often  seen  at  the 
distance  of  many  yards,  in  some  neighbouring  part  of  the  morass,  a 
squeezing  up  of  pliant  strata,  the  amount  of  upheaval  depending  on 
the  volume  and  weight  of  materials  heaped  upon  the  embankment. 
In  1852  I  saw  a  remarkable  instance  of  such  a  downward  and 
lateral  pressure,  in  the  suburbs  of  Boston  (U.  S.),  near  the  South 
Cove.  With  a  view  of  converting  part  of  an  estuary  overflowed  at 
high  tide  into  dry  land,  they  had  thrown  into  it  a  vast  load  of  stones 
and  sand,  upwards  of  900,000  cubic  yards  in  volume.  Under  this 
weight  the  mud  had  sunk  down  many  yards  vertically.  Meanwhile 
the  adjoining  bottom  of  the  estuary,  supporting  a  dense  growth  of  salt- 
water plants,  only  visible  at  low  tide,  had  been  pushed  gradually 
upward,  in  the  course  of  many  months,  so  as  to  project  five  or  six 
feet  above  high  water  mark.  The  upraised  mass  was  bent  into  five  or 
six  anticlinal  folds,  and  below  the  upper  layer  of  turf,  consisting  of 
salt-marsh  plants,  mud  was  seen  above  the  level  of  high  tide,  full  of 
sea  shells,  such  as  Mya  arenaria,  Modiola  plicatula,  Sanguinolaria 

*  Quart.  Journ.  Geol.  Soc.  vol.  vii.  p.  22. 


CH  XL]  BURIED   FOREST   IN   NORFOLK.  137 

fusca,  Nassa  obsoleta,  Natica  triseriata,  and  others.  In  some  of 
these  curved  beds  the  layers  of  shells  were  quite  vertical.  The  up- 
raised area  was  75  feet  wide,  and  several  hundred  yards  long.  Were 
an  equal  load,  melted  out  of  icebergs  or  coast-ice,  thrown  down  on 
the  floor  of  a  sea,  consisting  of  soft  mud  and  sand,  similar  disturb- 
ances and  contortions  might  result  in  some  adjacent  pliant  strata, 
yet  the  underlying  more  solid  rocks  might  remain  undisturbed,  and 
newer  formations,  perfectly  horizontal,  might  be  afterwards  super- 
imposed. 

A  buried  forest  has  been  adverted  to  as  underlying  the  drift  on  the 
coast  of  Norfolk.  At  the  time  when  the  trees  grew,  there  must  have 
been  dry  land  over  a  large  area,  which  was  afterwards  submerged,  so 
as  to  allow  a  mass  of  stratified  and  unstratified  drift,  200  feet  and 
more  in  thickness,  to  be  superimposed.  The  undermining  of  the 
cliffs  by  the  sea  in  modern  times  has  enabled  us  to  demonstrate, 
beyond  all  doubt,  the  fact  of  this  superposition,  and  that  the  forest 
was  not  formed  along  the  present  coast-line.  Its  situation  implies  a 
subsidence  of  several  hundred  feet  since  the  commencement  of  the 
drift  period,  after  which  there  must  have  been  an  upheaval  of  the 
same  ground ;  for  the  forest  bed  of  Norfolk  is  now  again  so  high  as 
to  be  exposed  to  view  at  many  points  at  low  water ;  and  this  same 
upward  movement  may  explain  why  the  till,  which  is  conceived  to 
have  been  of  submarine  origin,  is  now  met  with  far  inland,  and  on  the 
summit  of  hills. 

The  boulder  formation  of  the  west  of  England,  observed  in  Lan- 
cashire, Cheshire,  Shropshire,  Staffordshire,  and  Worcestershire,  con- 
tains in  some  places  marine  shells  of  recent  species,  rising  to  various 
heights,  from  100  to  350  feet  above  the  sea.  The  erratics  have  come 
partly  from  the  mountains  of  Cumberland,  and  partly  from  those  of 
Scotland. 

But  it  is  on  the  mountains  of  North  Wales  that  the  "  Northern 
drift,"  with  its  characteristic  marine  fossils,  reaches  its  greatest  alti- 
tude. On  Moel  Tryfane,  near  the  Menai  Straits,  Mr.  Trimmer  met 
with  shells  of  the  species  commonly  found  in  the  drift  at  the  height 
of  1392  feet  above  the  level  of  the  sea. 

It  is  remarkable  that  in  the  same  neighbourhood  where  there  is 
evidence  of  so  great  a  submergence  of  the  land  during  part  of  the 
glacial  period,  we  have  also  the  most  decisive  proofs  yet  discovered 
in  the  British  Isles  of  sub-aerial  glaciers.  Dr.  Buckland  published 
in  1842  his  reasons  for  believing  that  the  Snowdonian  mountains  in 
Caernarvonshire  were  formerly  covered  with  glaciers,  which  ra- 
diated from  the  central  heights  through  the  seven  principal  valleys 
of  that  chain,  where  striae  and  flutings  are  seen  on  the  polished  rocks 
directed  towards  as  many  different  points  of  the  compass.  He  also 
described  the  "  moraines  "  of  the  ancient  glaciers,  and  the  rounded 
"  bosses "  or  small  flattened  domes  of  polished  rock,  such  as  the 
action  of  moving  glaciers  is  known  to  produce  in  Switzerland,  when 
gravel,  sand,  and  boulders,  underlying  the  ice,  are  forced  along  over 
a  foundation  of  hard  stone.  Mr.  Darwin,  and  subsequently  Prof. 


138  FOSSIL    REMAINS    IN    DRIFT  [Cn.  XII. 

Ramsay,  have  confirmed  Dr.  Buckland's  views  in  regard  to  these 
Welsh  glaciers.  Nor  indeed  was  it  to  be  expected  that  geologists 
should  discover  proofs  of  icebergs  having  abounded  in  the  area  now 
occupied  by  the  British  Isles  in  the  Pleistocene  period  without  some- 
times meeting  with  the  signs  of  contemporaneous  glaciers  which 
covered  hills  even  of  moderate  elevation  between  the  50th  and  60th 
degrees  of  latitude. 

In  Ireland  the  "  drift "  exhibits  the  same  general  characters  and 
fossil  remains  as  in  Scotland  and  England  ;  but  in  the  southern  part 
of  that  island,  Prof.  E.  Forbes  and  Capt.  James  found  in  it  some 
shells  which  show  that  the  glacial  sea  communicated  with  one  in- 
habited by  a  more  southern  fauna.  Among  other  species  in  the 
south,  they  mention  at  Wexford  and  elsewhere  the  occurrence  of 
Nucula  Cobboldice  (see  fig.  125.  p.  156.)  and  Turritella  incrassata 
(a  crag  fossil) ;  also  a  southern  form  of  Fusus,  and  a  Mitra  allied  to 
a  Spanish  species.  * 


CHAPTER  XIL 

Difficulty  of  interpreting  the  phenomena  of  drift  before  the  glacial  hypothesis  was 
adopted— Effects  of  intense  cold  in  augmenting  the  quantity  of  alluvium  — 
Analogy  of  erratics  and  scored  rocks  in  North  America  and  Europe  —  Bayfield 
on  shells  in  drift  of  Canada  —  Great  subsidence  and  re -elevation  of  land  from  the 
sea,  required  to  account  for  glacial  appearances — Why  organic  remains  so  rare 
in  northern  drift  —  Mastodon  giganteus  in  United  States — Many  shells  and 
some  quadrupeds  survived  the  glacial  cold — Alps  an  independent  centre  of 
dispersion  of  erratics  —Alpine  blocks  on  the  Jura — Whether  transported  by 
glaciers  or  floating  ice — Recent  transportation  of  erratics  from  the  Andes  to 
Chiloe — Meteorite  in  Asiatic  drift. 

IT  will  appear  from  what  was  said  in  the  last  chapter  of  the  marine 
shells  characterizing  the  boulder  formation,  that  nine-tenths  or  more 
of  them  belong  to  species  still  living.  The  superficial  position  of 
"  the  drift "  is  in  perfect  accordance  with  its  imbedded  organic  re- 
mains, leading  us  to  refer  its  origin  to  a  modern  period.  If,  then, 
we  encounter  so  much  difficulty  in  the  interpretation  of  monuments 
relating  to  times  so  near  our  own — if  in  spite  of  their  recent  date 
they  are  involved  in  so  much  obscurity — the  student  may  ask,  not 
without  reasonable  alarm,  how  we  can  hope  to  decipher  the  records 
of  remoter  ages. 

To  remove  from  the  mind  as  far  as  possible  this  natural  feeling  of 
discouragement,  I  shall  endeavour  in  this  chapter  to  prove  that  what 
seems  most  strikingly  anomalous,  in  the  "  erratic  formation,"  as  some 
call  it,  is  really  the  result  of  that  glacial  action  which  has  already  been 

*  Forbes,  Memoirs  of  Geol.  Survey  of  Great  Britain,  vol.  i.  p.  377. 


CH.  XII.]      GLACIAL  PHENOMENA  OF  NORTHERN  ORIGIN.      139 

alluded  to.  If  so,  it  was  to  be  expected  that  so  long  as  the  true  origin 
of  so  singular  a  deposit  remained  undiscovered,  erroneous  theories  and 
terms  would  be  invented  in  the  effort  to  solve  the  problem.  These 
inventions  would  inevitably  retard  the  reception  of  more  correct 
views  which  a  wider  field  of  observation  might  afterwards  suggest. 

The  term  "  diluvium  *  was  for  a  time  the  popular  name  of  the 
boulder  formation,  because  it  was  referred  by  some  to  the  deluge, 
while  others  retained  the  name  as  expressive  of  their  opinion  that  a 
series  of  diluvial  waves  raised  by  hurricanes  and  storms,  or  by  earth- 
quakes, or  by  the  sudden  upheaval  of  land  from  the  bed  of  the  sea, 
had  swept  over  the  continents,  carrying  with  them  vast  masses  of 
mud  and  heavy  stones,  and  forcing  these  stones  over  rocky  surfaces 
so  as  to  polish  and  imprint  upon  them  long  furrows  and  striae. 

But  no  explanation  was  offered  why  such  agency  should  have  been 
developed  more  energetically  in  modern  times  than  at  former  periods 
of  the  earth's  history,  or  why  it  should  be  displayed  in  its  fullest 
intensity  in  northern  latitudes ;  for  it  is  important  to  insist  on  the 
fact,  that  the  boulder  formation  is  a  northern  phenomenon.  Even 
the  southern  extension  of  the  drift,  or  the  large  erratics  found  in  the 
Alps  and  the  surrounding  lands,  especially  their  occurrence  round 
the  highest  parts  of  the  chain,  offers  such  an  exception  to  the  general 
rule  as  confirms  the  glacial  hypothesis ;  for  it  shows  that  the  trans- 
portation of  stony  fragments  to  great  distances,  and  the  striation, 
polishing,  and  grooving  of  solid  floors  of  rock,  are  here  again  intimately 
connected  with  accumulations  of  perennial  snow  and  ice. 

That  there  is  some  intimate  connection  between  a  cold  or  northern 
climate  and  the  various  geological  appearances  now  commonly  called 
glacial,  cannot  be  doubted  by  any  one  who  has  compared  the  countries 
bordering  the  Baltic  with  those  surrounding  the  Mediterranean.  The 
smoothing  and  striation  of  rocks  and  erratics,  are  traced  from  the 
sea-shore  to  the  height  of  3000  feet  above  the  level  of  the  Baltic, 
whereas  such  phenomena  are  wholly  wanting  in  countries  bordering 
the  Mediterranean ;  and  their  absence  is  still  more  marked  in  the 
equatorial  parts  of  Asia,  Africa,  and  America ;  but  when  we  cross 
the  southern  tropic,  and  reach  Chili  and  Patagonia,  we  again  en- 
counter the  boulder  formation,  between  the  latitude  41°  S.  and  Cape 
Horn,  with  precisely  the  same  characters  which  it  assumes  in  Europe. 
The  evidence  as  to  climate  derived  from  the  organic  remains  of  the 
drift  is,  as  we  have  seen,  in  perfect  harmony  with  the  conclusions 
above  alluded  to,  the  former  habits  of  the  species  of  mollusca  being 
accurately  ascertainable,  inasmuch  as  they  belong  to  species  still  living, 
and  known  to  have  at  present  a  wide  range  in  northern  seas. 

But  if  we  are  correct  in  assuming  that  the  northern  hemisphere 
was  considerably  colder  than  now  during  the  period  under  considera- 
tion, owing  probably  to  the  greater  area  and  height  of  arctic  lands, 
and  to  the  quantity  of  icebergs  which  such  a  geographical  state  of 
things  would  generate,  it  may  be  well  to  reflect  before  we  proceed 
farther  on  the  entire  modification  which  extreme  cold  would  produce 
in  the  operation  of  those  causes  spoken  of  in  the  sixth  chapter  as 


140      GLACIAL  PHENOMENA  OF  NORTHERN  ORIGIN.       [Cn.  XII. 

most  active  in  the  formation  of  alluvium.  A  large  part  of  the 
materials  derived  from  the  detritus  of  rocks,  which  in  warm  climates 
would  go  to  form  deltas,  or  would  be  regularly  stratified  by  marine 
currents,  would,  under  arctic  influences,  assume  a  superficial  and 
alluvial  character.  Instead  of  mud  being  carried  farther  from  a 
coast  than  sand,  and  sand  farther  out  than  pebbles,  —  instead  of  dense 
stratified  masses  being  heaped  up  in  limited  areas,  along  the  borders 
of  continents, — nearly  the  whole  materials,  whether  coarse  or  fine, 
would  be  conveyed  by  ice  to  equal  distances,  and  huge  fragments, 
which  water  alone  could  never  move,  would  be  borne  for  hundreds 
of  miles  without  having  their  edges  worn  or  fractured :  and  the  earthy 
and  stony  masses,  when  melted  out  of  the  frozen  rafts,  would  be 
scattered  at  random  over  the  submarine  bottom,  whether  on  moun- 
tain tops  or  in  low  plains,  with  scarcely  any  relation  to  the  inequal- 
ities of  the  ground,  settling  on  the  crests  or  ridges  of  hills  in  tranquil 
water  as  readily  as  in  valleys  and  ravines.  Occasionally,  in  those 
deep  and  uninhabited  parts  of  the  ocean,  never  reached  by  any  but 
the  finest  sediment  in  a  normal  state  of  things,  the  bottom  would 
become  densely  overspread  by  gravel,  mud,  and  boulders. 

In  the  Western  Hemisphere,  both  in  Canada  and  as  far  south  as 
the  40th  and  even  38th  parallel  of  latitude  in  the  United  States,  we 
meet  with  a  repetition  of  all  the  peculiarities  which  distinguish  the 
European  boulder  formation.  Fragments  of  rock  have  travelled  for 
great  distances  from  north  to  south :  the  surface  of  the  subjacent  rock 
is  smoothed,  striated,  and  fluted ;  unstratified  mud  or  till  containing 
boulders  is  associated  with  strata  of  loam,  sand,  and  clay,  usually 
devoid  of  fossils.  Where  shells  are  present,  they  are  of  species  still 
living  in  northern  seas,  and  half  of  them  identical  with  those  already 
enumerated  as  belonging  to  European  drift  10  degrees  of  latitude 
farther  north.  The  fauna  also  of  the  glacial  epoch  in  North  America 
is  less  rich  in  species  than  that  now  inhabiting  the  adjacent  sea, 
whether  in  the  Gulf  of  St.  Lawrence,  or  off  the  shores  of  Maine,  or 
in  the  Bay  of  Massachusetts.  At  the  southern  extremity  of  its 
course,  moreover,  it  presents  an  analogy  with  the  drift  of  the  south 
of  Ireland,  by  blending  with  a  more  southern  fauna,  as  for  example 
at  Brooklyn  near  New  York,  in  lat.  41°  N.,  where,  according  to  MM. 
Eedfield  and  Desor,  Venus  mercenaria  and  other  southern  species  of 
shells  begin  to  occur  as  fossils  in  the  drift. 

The  extension  on  the  American  continent  of  the  range  of  erratics 
during  the  Pleistocene  period  to  lower  latitudes  than  they  reached  in 
Europe,  agrees  well  with  the  present  southward  deflection  of  the 
isothermal  lines,  or  rather  the  lines  of  equal  winter  temperature. 
It  seems  that  formerly,  as  now,  a  more  extreme  climate  and  a  more 
abundant  supply  of  floating  ice  prevailed  on  the  western  side  of  the 
Atlantic. 

Another  resemblance  between  the  distribution  of  the  drift  fossils 
in  Europe  and  North  America  has  yet  to  be  pointed  out.  In  Nor- 
way, Sweden,  and  Scotland,  as  in  Canada  and  the  United  States, 
the  marine  shells  are  confined  to  very  moderate  elevations  above  the 


Cm  XII.] 


DRIFT   SHELLS   IN   CANADA. 


141 


sea  (between  100  and  700  feet),  while  the  erratic  blocks  and  the 
grooved  and  polished  surfaces  of  rock  extend  to  elevations  of  several 
thousand  feet. 

I  described  in  1839  the  fossil  shells  collected  by  Captain  Bayfield 
from  strata  of  drift  at  Beauport  near  Quebec,  in  lat.  47°,  and  drew 
from  them  the  inference  that  they  indicated  a  more  northern  climate, 
the  shells  agreeing  in  great  part  with  those  of  Uddevalla  in  Sweden.* 
The  shelly  beds  attain  at  Beauport  and  the  neighbourhood  a  height 
of  200,  300,  and  sometimes  400  feet  above  the  sea,  and  dispersed 
through  some  of  them  are  large  boulders  of  granite,  which  could  not 
have  been  propelled  by  a  violent  current,  because  the  accompanying 
fragile  shells  are  almost  all  entire.  They  seem,  therefore,  said  Captain 
Bayfield,  writing  in  1838,  to  have  been  dropped  down  from  melting 
ice,  like  similar  stones  which  are  now  annually  deposited  in  the 
St.  Lawrence. f  I  visited  this  locality  in  1842,  and  made  the  annexed 
section,  fig.  123.,  which  will  give  an  idea  of  the  general  position  of 

Fig.  123- 


K.  Mr.  Ryland's  house. 

h.    Clay  and  sand  of  higher  grounds,  with 

Saricava,  &c. 
'g.  Gravel  with  boulders. 
/.    Mass  of  Saxicava  rugosa,  12  feet  thick. 
c.   Sand  and  loam  with  Mya  truncata,  Sca- 

laria  Grtenlandica,  &c. 


d.  Drift,  with  boulders  of  syenite,  &c. 

c.  Yellow  sand. 

b.  Laminated  clay,  25  fest  thick. 

A.  Horizontal  lower  Silurian  strata. 

B.  Valley  re-excavated. 


the  drift  in  Canada  and  the  United  States.  I  imagine  that  the  whole 
of  the  valley  B  was  once  filled  up  with  the  beds  b,  c,  d,  e,  f,  which  were 
deposited  during  a  period  of  subsidence,  and  that  subsequently  the 
higher  country  (h)  was  submerged  and  overspread  with  drift.  The 
partial  re-excavation  of  B  took  place  when  this  region  was  again 
uplifted  above  the  sea  to  its  present  height.  Among  the  twenty-three 
species  of  fossil  shells  collected  by  me  from  these  beds  at  Beauport, 
all  were  of  recent  northern  species,  except  one,  which  is  unknown  as 

Fig.  124. 


a.  Outside. 


Astarte  Laurentiana. 
b.  Inside  of  right  valve. 


c.  Left  valve. 


living,  and  may  be  extinct  (see  fig.  124.).     I  also  examined  the  same 
formation  farther  up  the  valley  of  the  St.  Lawrence,  in  the  suburbs 


*  Geol.  Trans.  2d  series,  vol.  vi.  p.  135, 
Mr.  Smith  of  JordanhilJ  had  arrived  at 
similar  conclusions  as  to  climate  from  the 


shells  of  the  Scotch  Pleistocene  deposits. 
f  Proceedings  of  Geol    Soc.  No.  63. 
p.  119. 


142  SUBSIDENCE   IN   DRIFT    PERIOD.  [Cn.  XII. 

of  Montreal,  where  some  of  the  beds  of  loam  are  filled  with  great 
numbers  of  the  Mytilus  edulis,  or  our  common  European  mussel, 
retaining  both  its  valves  and  purple  colour.  This  shelly  deposit, 
containing  Saxicava  rugosa  and  other  characteristic  marine  shells, 
also  occurs  at  an  elevated  point  on  the  mountain  of  Montreal,  450  feet 
above  the  level  of  the  sea.* 

In  my  account  of  Canada  and  the  United  States,  published  in  1845, 
I  announced  the  conclusion  to  which  I  had  then  arrived,  that  to 
explain  the  position  of  the  erratics  and  the  polished  surfaces  of  rocks, 
and  their  striae  and  flutings,  we  must  assume  first  a  gradual  sub- 
mergence of  the  land  in  North  America,  after  it  had  acquired  its 
present  outline  of  hill  and  valley,  cliff  and  ravine,  and  then  its 
re-emergence  from  the  ocean.  When  the  land  was  slowly  sinking, 
the  sea  which  bordered  it  was  covered  with  islands  of  floating  ice 
coming  from  the  north,  which,  as  they  grounded  on  the  coast  and  on 
shoals,  pushed  along  such  loose  materials  of  sand  and  pebbles  as  lay 
strewed  over  the  bottom.  By  this  force  all  angular  and  projecting 
points  were  broken  off,  and  fragments  of  hard  stone,  frozen  into  the 
lower  surface  of  the  ice,  had  power  to  scoop  out  grooves  in  the 
subjacent  solid  rock.  The  sloping  beach,  as  well  as  the  floor  of  the 
ocean,  might  be  polished  and  scored  by  this  machinery ;  but  no  flood 
of  water,  however  violent,  or  however  great  the  quantity  of  detritus 
or  size  of  the  rocky  fragments  swept  along  by  it,  could  produce  such 
long,  perfectly  straight  and  parallel  furrows,  as  are  everywhere  visible 
in  the  Niagara  district,  and  generally  in  the  region  north  of  the  40th 
parallel  of  latitude,  f 

By  the  hypothesis  of  such  a  slow  and  gradual  subsidence  of  the 
land  we  may  account  for  the  fact  that  almost  everywhere  in  N. 
America  and  Northern  Europe  the  boulder  formation  rests  on  a 
polished  and  furrowed  surface  of  rock,  —  a  fact  by  no  means  obliging 
us  to  imagine,  as  some  think,  that  the  polishing  and  grooving  action 
was,  as  a  whole,  anterior  in  date  to  the  transportation  of  the  erratics. 
During  the  successive  depression  of  high  land,  varying  originally  in 
height  from  1000  to  3000  feet  above  the  sea  level,  every  portion  of 
the  surface  would  be  brought  down  by  turns  to  the  level  of  the  ocean, 
so  as  to  be  converted  first  into  a  coast-line,  and  then  into  a  shoal ;  and 
at  length,  after  being  well  scored  by  the  stranding  upon  it  year  after 
year  of  large  masses  of  coast-ice  and  occasional  icebergs,  might  be 
sunk  to  a  depth  of  several  hundred  fathoms.  By  the  constant  de- 
pression of  land,  the  coast  would  recede  farther  and  farther  from  the 
successively  formed  zones  of  polished  and  striated  rock,  each  outer 
zone  becoming  in  its  turn  so  deep  under  water  as  to  be  no  longer 
grated  upon  by  the  heaviest  icebergs.  Such  sunken  areas  would 
then  simply  serve  as  receptacles  of  mud,  sand,  and  boulders  dropped 
from  melting  ice,  perhaps  to  a  depth  scarcely,  if  at  all,  inhabited  by 
testacea  and  zoophytes.  Meanwhile,  during  the  formation  of  the 
unstratified  and  unfossiliferous  mass  in  deeper  water,  the  smoothing 

*  Travels  in  N.  America,  vol.  ii.  p.  141.  f  Ibid,  p.  99.  ehap.  xix. 


OH.  XII.]  STRIATED   PEBBLES   AND   BOULDERS.  143 

and  furrowing  of  shoals  and  beaches  would  still  go  on  elsewhere 
upon  and  near  the  coast  in  full  activity.  If  at  length  the  subsidence 
should  cease,  and  the  direction  of  the  movement  of  the  earth's  crust 
be  reversed,  the  sunken  area  covered  with  drift  would  be  slowly 
reconverted  into  land.  The  boulder  deposit,  before  emerging,  would 
then  for  a  time  be  brought  within  the  action  of  the  waves,  tides, 
and  currents,  so  that  its  upper  portion,  being  partially  disturbed, 
would  have  its  materials  rearranged  and  stratified.  Streams  also 
flowing  from  the  land  would  in  some  places  throw  down  layers  of 
sediment  upon  the  till.  In  that  case,  the  order  of  superposition  will 
be,  first  and  uppermost,  sand,  loam,  and  gravel  occasionally  fossili- 
ferous ;  secondly,  an  unstratified  and  unfossiliferous  mass  called  till, 
for  the  most  part  of  much  older  date  than  the  preceding,  with  angular 
erratics,  or  with  boulders  interspersed ;  and,  thirdly,  beneath  the  whole, 
a  surface  of  polished  and  furrowed  rock.  Such  a  succession  of  events 
seems  to  have  prevailed  very  widely  on  both  sides  of  the  Atlantic,  the 
travelled  blocks  having  been  carried  in  general  from  the  North  Pole 
southwards,  but  mountain  chains  having  in  some  cases  served  as  inde- 
pendent centres  of  dispersion,  of  which  the  Alps  present  the  most 
conspicuous  example. 

It  is  by  no  means  rare  to  meet  with  boulders  imbedded  in  drift 
which  are  worn  flat  on  one  or  more  of  their  sides,  the  surface  being 
at  the  same  time  polished,  furrowed,  and  striated.  They  may  have 
been  so  shaped  in  a  glacier  before  they  reached  the  sea,  or  when  they 
were  fixed  in  the  bottom  of  an  iceberg  as  it  ran  aground.  We  learn 
from  Mr.  Charles  Martins  that  the  glaciers  of  Spitzbergen  project 
from  the  coast  into  a  sea  between  100  and  400  feet  deep  ;  and  that 
numbers  of  striated  pebbles  or  blocks  are  there  seen  to  disengage 
themselves  from  the  overhanging  masses  of  ice  as  they  melt,  so  as  to 
fall  at  once  into  deep  water.* 

That  they  should  retain  such  markings  when  again  upraised  above 
the  sea  ought  not  to  surprise  us,  when  we  remember  that  rippled 
sands,  and  the  cracks  in  clay  dried  between  high  and^ow  water,  and 
the  foot-tracks  of  animals  and  rain-drops  impressed  on  mud,  and  other 
superficial  markings,  are  all  found  fossil  in  rocks  of  various  ages. 

On  the  other  hand,  it  is  not  difficult  to  account  for  the  absence  in 
many  districts  of  striated  and  scored  pebbles  and  boulders  in  glacial 
deposits,  for  they  may  have  been  exposed  to  the  action  of  the  waves 
on  a  coast  while  it  was  sinking  beneath  or  rising  above  the  sea.  No 
shingle  on  an  ordinary  sea-beach  exhibits  such  striae,  and  at  a  very 
short  distance  from  the  termination  of  a  glacier  every  stone  in  the 
bed  of  the  torrent  which  gushes  out  from  the  melting  ice  is  found  to 
have  lost  its  glacial  markings  by  being  rolled  for  a  distance  even  of  a 
few  hundred  yards. 

The  usual  dearth  of  fossil  shells  in  glacial  clays  well  fitted  to  pre- 
serve organic  remains  may,  perhaps,  be  owing,  as  already  hinted,  to 
the  absence  of  testacea  in  the  deep  sea,  where  the  undisturbed  accu- 

*  Bulletin  Soc.  Geol.  de  France,  torn.  iv.  2de  ser.  p.  1121. 


144  MASTODON    GIGANTEUS.  [Cu.  XII. 

mulation  of  boulders  melted  out  of  coast-ice  and  icebergs  may  take 
place.  In  the  ./Egean  and  other  parts  of  the  Mediterranean,  the  zero  of 
animal  life,  according  to  Prof.  E.  Forbes,  is  approached  at  a  depth  of 
about  300  fathoms.  In  tropical  seas  it  would  descend  farther  down, 
just  as  vegetation  ascends  higher  on  the  mountains  of  hot  countries. 
Near  the  pole,  on  the  other  hand,  the  same  zero  would  be  reached 
much  sooner  both  on  the  hills  and  in  the  sea.  If  the  ocean  was  filled 
with  floating  bergs,  and  a  low  temperature  prevailed  in  the  northern 
hemisphere  during  the  glacial  period,  even  the  shallow  part  of  the 
sea  might  have  been  uninhabitable,  or  very  thinly  peopled  with  living 
beings.  It  may  also  be  remarked  that  the  melting  of  ice  in  some 
fiords  in  Norway  freshens  the  water  so  as  to  destroy  marine  life,  and 
famines  have  been  caused  in  Iceland  by  the  stranding  of  icebergs 
drifted  from  the  Greenland  coast,  which  have  required  several  years 
to  melt,  and  have  not  only  injured  the  hay  harvest  by  cooling  the 
atmosphere,  but  have  driven  away  the  fish  from  the  shore  by  chilling 
and  freshening  the  sea. 

If  the  cold  of  the  glacial  epoch  came  on  slowly,  if  it  was  long 
before  it  reached  its  greatest  intensity,  and  again  if  it  abated  gradu- 
ally, we  may  expect  to  find  the  earliest  and  latest  formed  drift  less 
barren  of  organic  remains  than  that  deposited  during  the  coldest 
period.  We  may  also  expect  that  along  the  southern  limits  of  the 
drift  during  the  whole  glacial  epoch,  there  would  be  an  intimate 
association  of  transported  matter  of  northern  origin  with  fossil- 
bearing  sediment,  whether  marine  or  freshwater,  belonging  to  more 
southern  seas,  rivers,  and  continents. 

That  in  the  United  States,  the  Mastodon  giganteus  was  very 
abundant  after  the  drift  period  is  evident  from  the  fact  that  entire 
skeletons  of  this  animal  are  met  with  in  bogs  and  lacustrine  deposits 
occupying  hollows  in  the  drift.  They  sometimes  occur  in  the  bottom 
even  of  small  ponds  recently  drained  by  the  agriculturist  for  the  sake 
of  the  shell  marl.  I  examined  one  of  these  spots  at  Geneseo  in  the 
state  of  New  York,  from  which  the  bones,  skull,  and  tusk  of  a  Mas- 
todon had  been  procured  in  the  marl  below  a  layer  of  black  peaty 
earth,  and  ascertained  that  all  the  associated  freshwater  and  land 
shells  were  of  a  species  now  common  in  the  same  district.  They  con- 
sisted of  several  species  of  Lymnea,  of  Planorbis  bicarinatus,  Physa 
heterostropha,  &c. 

In  1845  no  less  than  six  skeletons  of  the  same  species  of  Mastodon 
were  found  in  Warren  County,  New  Jersey,  6  feet  below  the  surface, 
by  a  farmer  who  was  digging  out  the  rich  mud  from  a  small  pond 
which  he  had  drained.  Five  of  these  skeletons  were  lying  together, 
and  a  large  part  of  the  bones  crumbled  to  pieces  as  soon  as  they  were 
exposed  to  the  air.  But  nearly  the  whole  of  the  other  skeleton,  which 
lay  about  10  feet  apart  from  the  rest,  was  preserved  entire,  and 
proved  the  correctness  of  Cuvier's  conjecture  respecting  this  extinct 
animal,  namely,  that  it  had  twenty  ribs  like  the  living  elephant. 
From  the  clay  in  the  interior  within  the  ribs,  just  where  the  contents 
of  the  stomach  might  naturally  have  been  looked  for,  seven  bushels  of 


CH.  XII.]  EXTINCT   MAMMALIA  ABOVE   DRIFT.  145 

vegetable  matter  were  extracted.  I  submitted  some  of  this  matter  to 
Mr.  A.  Henfrey  of  London  for  microscopic  examination,  and  he 
informs  me  that  it  consists  of  pieces  of  small  twigs  of  a  coniferous 
tree  of  the  Cypress  family,  probably  the  young  shoots  of  the  white 
cedar,  Thuja  occidentalis,  still  a  native  of  North  America,  on  which 
therefore  we  may  conclude  that  this  extinct  Mastodon  once  fed. 

Another  specimen  of  the  same  quadruped,  the  most  complete  and 
probably  the  largest  ever  found,  was  exhumed  in  1845  in  the  town  of 
Newburg,  New  York,  the  length  of  the  skeleton  being  25  feet,  and 
its  height  12  feet.  The  anchylosing  of  the  last  two  ribs  on  the  right 
side  afforded  Dr.  John  C.  Warren  a  true  gauge  for  the  space  occu- 
pied by  the  intervertebrate  substance,  so  as  to  enable  him  to  form  a 
correct  estimate  of  the  entire  length.  The  tusks  when  discovered 
were  10  feet  long,  but  a  part  only  could  be  preserved.  The  large 
proportion  of  animal  matter  in  the  tusk,  teeth,  and  bones  of  some  of 
these  fossil  mammalia  is  truly  astonishing.  It  amounts  in  some  cases, 
as  Dr.  C.  T.  Jackson  has  ascertained  by  analysis,  to  27  per  cent. ;  so 
that  when  all  the  earthy  ingredients  are  removed  by  acids,  the  form  of 
the  bone  remains  as  perfect,  and  the  mass  of  animal  matter  is  almost 
as  firm,  as  in  a  recent  bone  subjected  to  similar  treatment. 

It  would  be  rash,  however,  to  infer  from  such  data  that  these  qua- 
drupeds were  mired  in  modern  times,  unless  we  use  that  term  strictly 
in  a  geological  sense.  I  have  shown  that  there  is  a  fluviatile  de- 
posit in  the  valley  of  the  Niagara,  containing  shells  of  the  genera 
Melania,  Lymnea,  Planorbis,  Valvata,  Cyclas,  Unio,  Helix,  &c., 
all  of  recent  species,  from  which  the  bones  of  the  great  Mastodon 
have  been  taken  in  a  very  perfect  state.  Yet  the  whole  excavation  of 
the  ravine,  for  many  miles  below  the  Falls,  has'  been  slowly  effected 
since  that  fluviatile  deposit  was  thrown  down. 

Whether  or  not,  in  assigning  a  period  of  more  than  30,000  years  for 
the  recession  of  the  Falls  from  Queenstown  to  their  present  site,  I  have 
over  or  under  estimated  the  time  required  for  that  operation,  no  one 
can  doubt  that  a  vast  number  of  centuries  must  have  elapsed  before 
so  great  a  series  of  geographical  changes  were  brought  about  as  have 
occurred  since  the  entombment  of  this  elephantine  quadruped.  The 
freshwater  gravel  which  encloses  it  is  decidedly  of  much  more  modern 
origin  than  the  drift  or  boulder  clay  of  the  same  region.* 

Other  extinct  animals  accompany  the  Mastodon  giganteus  in  the 
post-glacial  deposits  of  the  United  States,  among  which  the  Castoroides 
ohioensis,  Foster  and  Wyman,  a  huge  rodent  allied  to  the  beaver, 
and  Capybara  may  be  mentioned.  But  whether  the  "loess,"  and 
other  freshwater  and  marine  strata  of  the  Southern  States,  in  which 
skeletons  of  the  same  Mastodon  are  mingled  with  the  bones  of  the 
Megatherium,  Mylodon,  and  Megalonyx,  were  contemporaneous  with 
the  drift,  or  were  of  subsequent  date,  is  a  chronological  question  still 
open  to  discussion.  It  appears  clear,  however,  from  what  we  know 
of  the  tertiary  fossils  of  Europe — and  I  believe  the  same  will  hold 

*  Travels  in  N.  America,  vol.  i.  chap,  ii.,  and  Principles  of  Geol.  chap.  xir. 


146  CLIMATE   OP   DRIFT   PERIOD.  [Cn,  XII. 

true  in  North  America — that  many  species  of  testacea  and  some 
mammalia  which  existed  prior  to  the  glacial  epoch,  survived  that 
era.  As  European  examples  among  the  warm-blooded  quadrupeds, 
the  Elephas primigenius  and  Rhinoceros  tichorhinus  may  be  mentioned. 
As  to  the  shells,  whether  freshwater,  terrestrial,  or  marine,  they  need 
not  be  enumerated  here,  as  allusion  will  be  made  to  them  in  the 
sequel,  when  the  pliocene  tertiary  fossils  of  Suffolk  are  described. 
The  fact  is  important,  as  refuting  the  hypothesis  that  the  cold  of  the 
glacial  period  was  so  intense  and  universal  as  to  annihilate  all  living 
creatures  throughout  the  globe. 

That  the  cold  was  greater  for  a  time  than  it  is  now  in  certain  parts 
of  Siberia,  Europe,  and  North  America,  will  not  be  disputed ;  but, 
before  we  can  infer  the  universality  of  a  colder  climate,  we  must 
ascertain  what  was  the  condition  of  other  parts  of  the  northern,  and 
of  the  whole  southern,  hemisphere  at  the  time  when  the  Scandinavian, 
British,  and  Alpine  erratics  were  transported  into  their  present 
position.  It  must  not  be  forgotten  that  a  great  deposit  of  drift  and 
erratic  blocks  is  now  in  full  progress  of  formation  in  the  southern 
hemisphere,  in  a  zone  corresponding  in  latitude  to  the  Baltic,  and  to 
Northern  Italy,  Switzerland,  France,  and  England.  Should  the  un- 
even bed  of  the  southern  ocean  be  hereafter  converted  by  upheaval 
into  land,  the  hills  and  valleys  will  be  strewed  over  with  transported 
fragments,  some  derived  from  the  antarctic  continent,  others  from 
islands  covered  with  glaciers,  like  South  Georgia,  which  must  now  be 
centres  of  the  dispersion  of  drift,  although  situated  in  a  latitude 
agreeing  with  that  of  the  Cumberland  mountains  in  England. 

Not  only  are  these  operations  going  on  between  the  45th  and  60th 
parallels  of  latitude  south  of  the  line,  while  the  corresponding  zone 
of  Europe  is  free  from  ice ;  but,  what  is  still  more  worthy  of  remark, 
we  find  in  the  southern  hemisphere  itself,  only  900  miles  distant 
from  South  Georgia,  where  the  perpetual  snow  reaches  to  the  sea- 
beach,  lands  covered  with  forest,  as  in  Terra  del  Fuego.  There  is 
here  no  difference  of  latitude  to  account  for  the  luxuriance  of 
vegetation  in  one  spot,  and  the  absolute  want  of  it  in  the  other ;  but 
among  other  refrigerating  causes  in  South  Georgia  may  be  enu- 
merated the  countless  icebergs  which  float  from  the  antarctic  zone, 
and  which  chill,  as  they  melt,  the  waters  of  the  ocean,  and  the  sur- 
rounding air,  which  they  fill  with  dense  fogs. 

I  have  endeavoured  in  the  "  Principles  of  Geology,"  chapters 
7  and  8.,  to  point  out  the  intimate  connexion  of  climate  and  the 
physical  geography  of  the  globe,  and  the  dependence  of  the  mean 
annual  temperature,  not  only  on  the  height  of  the  dry  land,  but  on 
its  distribution  in  high  or  low  latitudes  at  particular  epochs.  If, 
for  example,  at  certain  periods  of  the  past,  the  antarctic  land  was  less 
elevated  and  less  extensive  than  now,  while  that  at  the  north  pole 
was  higher  and  more  continuous,  the  conditions  of  the  northern 
and  southern  hemispheres  might  have  been  the  reverse  of  what  we 
now  witness  in  regard  to  climate,  although  the  mountains  of  Scan- 
dinavia, Scotland,  and  Switzerland  may  have  been  less  elevated  than 


CH.  XII.]  ALPINE   ERRATICS.  147 

* 

at  present.  But  if  in  both  of  the  polar  regions  a  considerable 
area  of  elevated  dry  land  existed,  such  a  concurrence  of  refrigerating 
conditions  in  both  hemispheres  might  have  created  for  a  time  an  in- 
tensity of  cold  never  experienced  since  ;  and  such  probably  was  the 
state  of  things  during  that  period  of  submergence  to  which  I  have 
alluded  in  this  chapter. 

Alpine  erratics. — Although  the  arctic  regions  constitute  the  great 
centre  from  which  erratics  have  travelled  southwards  in  all  directions 
in  Europe  and  North  America,  yet  there  are  some  mountains,  as  I 
have  already  stated,  like  those  of  North  Wales  and  the  Alps,  which 
have  served  as  separate  and  independent  centres  for  the  dispersion  of 
blocks.  In  illustration  of  this  fact,  the  Alps  deserve  particular  atten- 
tion not  only  from  their  magnitude,  but  because  they  lie  beyond  the 
ordinary  limits  of  the  "northern  drift"  of  Europe,  being  situated 
between  the  44th  and  47th  degrees  of  north  latitude.  On  the  flanks 
of  these  mountains,  and  on  the  Subalpine  ranges  of  hills  or  plains 
adjoining  them,  those  appearances  which  have  been  so  often  alluded 
to,  as  distinguishing  or  accompanying  the  drift,  between  the  50th  and 
70th  parallels  of  north  latitude,  suddenly  reappear,  to  assume  in  a 
more  southern  country  their  most  exaggerated  form.  Where  the 
Alps  are  highest,  the  largest  erratic  blocks  have  been  sent  forth  ;  as, 
for  example,  from  the  regions  of  Mont  Blanc  and  Monte  Rosa,  into 
the  adjoining  parts  of  France,  Switzerland,  Austria,  and  Italy ;  while 
in  districts  where  the  great  chain  sinks  in  altitude,  as  in  Carinthia, 
Carniola,  and  elsewhere,  no  such  rocky  fragments,  or  a  few  only  and 
of  smaller  bulk,  have  been  detached  and  transported  to  a  distance. 

In  the  year  1821,  M.  Venetz  first  announced  his  opinion  that  the 
Alpine  glaciers  must  formerly  have  extended  fap  beyond  their  present 
limits,  and  the  proofs  appealed  to  by  him  in  confirmation  of  this 
doctrine  were  afterwards  acknowledged  by  M.  Charpentier,  who 
strengthened  them  by  new  observations  and  arguments,  and  declared, 
in  1836,  his  conviction  that  the  glaciers  of  the  Alps  must  once  have 
reached  as  far  as  the  Jura,  and  have  carried  thither  their  moraines 
across  the  great  valley  of  Switzerland.  M.  Agassiz,  after  several  ex- 
cursions in  the  Alps  with  M.  Charpentier,  and  after  devoting  himself 
some  years  to  the  study  of  glaciers,  published,  in  1840,  an  admirable 
description  of  them  and  of  the  marks  which  attest  the  former  action 
of  great  masses  of  ice  over  the  entire  surface  of  the  Alps  and  the  sur- 
rounding country.  *  He  pointed  out  that  the  surface  of  every  large 
glacier  is  strewed  over  with  gravel  and  stones  detached  from  the 
surrounding  precipices  by  frost,  rain,  lightning,  or  avalanches.  And 
he  described  more  carefully  than  preceding  writers  the  long  lines  of 
these  stones,  which  settle  on  the  sides  of  the  glacier,  and  are  called 
the  lateral  moraines ;  those  found  at  the  lower  end  of  the  ice  being 
called  terminal  moraines.  Such  heaps  of  earth  and  boulders  every 
glacier  pushes  before  it  when  advancing,  and  leaves  behind  it  when 
retreating.  When  the  Alpine  glacier  reaches  a  lower  and  warmer 

*  Agassiz,  Etudes  sur  les  Glaciers,  and  Systeme  Glaciere. 
L  2 


148  MORAINES   OF    GLACIERS.  [Cn.  XII. 

situation,  about  3000  or  4000  feet  above  the  sea,  it  melts  so  rapidly 
that,  in  spite  of  the  downward  movement  of  the  mass,  it  can  advance 
no  farther.  Its  precise  limits  are  variable  from  year  to  year,  and  still 
more  so  from  century  to  century ;  one  example  being  on  record  of  a 
recession  of  half  a  mile  in  a  single  year.  We  also  learn  from  M. 
Venetz,  that  whereas,  between  the  eleventh  and  fifteenth  centuries,  all 
the  Alpine  glaciers  were  less  advanced  than  now,  they  began  in  the 
seventeenth  and  eighteenth  centuries  to  push  forward,  so  as  to  cover 
roads  formerly  open,  and  to  overwhelm  forests  of  ancient  growth. 

These  oscillations  enable  the  geologist  to  note  the  marks  which 
a  glacier  leaves  behind  it  as  it  retrogrades  ;  and  among  these  the  most 
prominent,  as  before  stated,  are  the  terminal  moraines,  or  mounds  of 
unstratified  earth  and  stones,  often  divided  by  subsequent  floods  into 
hillocks,  which  cross  the  valley  like  ancient  earth-works,  or  embank- 
ments made  to  dam  up  a  river.  Some  of  these  transverse  barriers 
were  formerly  pointed  out  by  Saussure  below  the  glacier  of  the  Rhone, 
as  proving  how  far  it  had  once  transgressed  its  present  boundaries. 
On  these  moraines  we  see  many  large  angular  fragments,  which, 
having  been  carried  along  on  the  surface  of  the  ice,  have  not  had 
their  edges  worn  off  by  friction  ;  but  the  greater  number  of  the 
boulders,  even  those  of  large  size,  have  been  well  rounded,  not  by  the 
power  of  water,  but  by  the  mechanical  force  of  the  ice,  which  has 
pushed  them  against  each  other,  or  against  the  rocks  flanking  the 
valley.  Others  have  fallen  down  the  numerous  fissures  which  in- 
tersect the  glacier,  where,  being  subject  to  the  pressure  of  the  whole 
mass  of  ice,  they  have  been  forced  along,  and  either  well  rounded  or 
ground  down  into  sand,  or  even  the  finest  mud,  of  which  the  moraine 
is  largely  constituted. 

As  the  terminal  moraines  are  the  most  prominent  of  all  the  monu- 
ments left  by  a  receding  glacier,  so  are  they  the  most  liable  to  obli- 
teration ;  for  violent  floods  or  debacles  are  often  occasioned  in  the 
Alps  by  the  sudden  bursting  of  what  are  called  glacier-lakes.  These 
temporary  sheets  of  water  are  caused  by  the  damming  up  of  a  river 
by  a  glacier  which  has  increased  during  a  succession  of  cold  seasons, 
and  descending  from  a  tributary  into  the  main  valley,  has  crossed  it 
from  side  to  side.  On  the  failure  of  this  icy  barrier,  the  accumulated 
waters  are  let  loose,  which  sweep  away  and  level  many  a  transverse 
mound  of  gravel  and  loose  boulders  below,  and  spread  their  materials 
in  confused  and  irregular  beds  over  the  river-plain. 

Another  mark  of  the  former  action  of  glaciers,  in  situations  where 
they  exist  no  longer,  is  the  polished,  striated,  and  grooved  surfaces  of 
rocks  already  alluded  to.  Stones  which  lie  underneath  the  glacier 
and  are  pushed  along  by  it,  sometimes  adhere  to  the  ice,  and  as  the 
mass  glides  slowly  along  at  the  rate  of  a  few  inches,  or  at  the  utmost 
two  or  three  feet,  per  day,  abrade,  groove,  and  polish  the  rock,  and 
the  larger  blocks  are  reciprocally  grooved  and  polished  by  the  rock 
on  their  lower  sides.  As  the  forces  both  of  pressure  and  propulsion 
are  enormous,  the  sand,  acting  like  emery,  polishes  the  surface ;  the 
pebbles,  like  coarse  gravers,  scratch  and  furrow  it;  and  the  large 


CH.  XII.]  ALPINE   ERRATICS   ON   THE   JURA.  149 

stones  scoop  out  grooves  in  it.  Another  effect  also  of  this  action, 
not  yet  adverted  to,  is  called  "roches  moutonnees."  Projecting  emi- 
nences of  rock  are  smoothed  and  worn  into  the  shape  of  flattened 
domes,  where  the  glaciers  have  passed  over  them. 

Although  the  surface  of  almost  every  kind  of  rock,  when  exposed 
in  the  open  air,  wastes  away  by  decomposition,  yet  some  retain  for 
ages  their  polished  and  furrowed  exterior  ;  and,  if  they  are  well  pro- 
tected by  a  covering  of  clay  or  turf,  these  marks  of  abrasion  seem 
capable  of  enduring  for  ever.  They  have  been  traced  in  the  Alps  to 
great  heights  above  the  present  glaciers,  and  to  great  horizontal  dis- 
tances beyond  them. 

There  are  also  found,  on  the  sides  of  the  Swiss  valleys,  round  and 
deep  holes  with  polished  sides,  such  holes  as  waterfalls  make  in  the 
solid  rock,  but  in  places  remote  from  running  waters,  and  where  the 
form  of  the  surface  will  not  permit  us  to  suppose  that  any  cascade 
could  ever  have  existed.  Similar  cavities  are  common  in  hard  rocks, 
such  as  gneiss  in  Sweden,  where  they  are  called  giant  caldrons,  and 
are  sometimes  10  feet  and  more  in  depth  ;  but  in  the  Alps  and  Jura 
they  often  pass  into  spoon-shaped  excavations  and  prolonged  gutters. 
We  learn  from  M.  Agassiz  that  hollows  of  this  form  are  now  cut  out 
by  streams  of  water  which,  after  flowing  along  the  surface  of  a 
glacier,  fall  into  open  fissures  in  the  ice  and  form  a  cascade.  Here  the 
falling  water,  causing  the  gravel  and  sand  at  the  bottom  to  rotate, 
cuts  out  a  round  cavity  in  the  rock.  But  as  the  glacier  moves  on, 
the  cascade  becomes  locomotive,  and  what  would  otherwise  have 
been  a  circular  hole  is  prolonged  into  a  deep  groove.  The  form  of 
the  rocky  bottom  of  the  valley  down  which  the  glacier  is  moving  causes 
the  rents  in  the  ice  and  these  locomotive  cascades  to  be  formed 
again  and  again,  year  after  year,  in  exactly  the  same  spots. 

Another  effect  of  a  glacier  is  to  lodge  a  ring  of  stones  round  the 
summit  of  a  conical  peak  which  may  happen  to  project  through  the  ice. 
If  the  glacier  is  lowered  greatly  by  melting,  these  circles  of  large 
angular  fragments,  which  are  called  "perched  blocks,"  are  left  in  a 
singular  situation  near  the  top  of  a  steep  hill  or  pinnacle,  the  lower 
parts  of  which  may  be  destitute  of  boulders. 

Alpine  blocks  on  the  Jura.  —  Now  some  or  all  the  marks  above 
enumerated,  —  the  moraines,  erratics,  polished  surfaces,  domes,  strise, 
caldrons,  and  perched  rocks,  are  observed  in  the  Alps  at  great  heights 
above  the  present  glaciers,  and  far  below  their  actual  extremities ; 
also  in  the  great  valley  of  Switzerland,  50  miles  broad ;  and  almost 
everywhere  on  the  Jura,  a  chain  which  lies  to  the  north  of  this 
valley.  The  average  height  of  the  Jura  is  about  one-third  that  of 
the  Alps,  and  it  is  now  entirely  destitute  of  glaciers ;  yet  it  presents 
almost  everywhere  similar  moraines,  and  the  same  polished  and 
grooved  surfaces  and  water-worn  cavities.  The  erratics,  moreover, 
which  cover  it,  present  a  phenomenon  which  has  astonished  and  per- 
plexed the  geologist  for  more  than  half  a  century.  No  conclusion 
can  be  more  incontestable  than  that  these  angular  blocks  of  granite, 
gneiss,  and  other  crystalline  formations,  came  from  the  Alps,  and  that 

L  3 


150  ALPINE    EKEATICS   ON   THE   JURA.  [Cn.  XII. 

they  have  been  brought  for  a  distance  of  50  miles  and  upwards  across 
one  of  the  widest  and  deepest  valleys  of  the  world ;  so  that  they  are 
now  lodged  on  the  hills  and  valleys  of  a  chain  composed  of  limestone 
and  other  formations,  altogether  distinct  from  those  of  the  Alps. 
Their  great  size  and  angularity,  after  a  journey  of  so  many  leagues, 
has  justly  excited  wonder;  for  hundreds  of  them  are  as  large  as  cot- 
tages ;  and  one  in  particular,  celebrated  under  the  name  of  Pierre  a 
Bot,  rests  on  the  side  of  a  hill  about  900  feet  above  the  lake  of  Neuf- 
chatel,  and  is  no  less  than  40  feet  in  diameter. 

It  will  be  remarked  that  these  blocks  on  the  Jura  offer  an  excep- 
tion to  the  rule  before  laid  down,  as  applicable  in  general  to  erratics, 
since  they  have  gone  from  south  to  north.  Some  of  the  largest 
masses  of  granite  and  gneiss  have  been  found  to  contain  50,000  and 
60,000  cubic  feet  of  stone,  and  one  limestone  block  at  Devens, 
near  Bex,  which  has  travelled  30  miles,  contains  161,000  cubic  feet, 
its  angles  being  sharp  and  unworn.* 

Von  Buch,  Escher,  and  Studer  have  shown,  from  an  examination 
of  the  mineral  composition  of  the  boulders,  that  those  on  the  western 
Jura,  near  Neufchatel,  have  come  from  the  region  of  Mont  Blanc 
and  the  Valais ;  those  on  the  middle  parts  of  the  Jura  from  the  Ber- 
nese Oberland ;  and  those  on  the  eastern  Jura  from  the  Alps  of  the 
small  cantons,  Glaris,  Schwytz,  Uri,  and  Zug.  The  blocks,  there- 
fore, of  these  three  great  districts  have  been  derived  from  parts  of 
the  Alps  nearest  to  the  localities  in  the  Jura  where  we  now  find  them, 
as  if  they  had  crossed  the  great  valley  in  a  direction  at  right  angles 
to  its  length ;  the  most  western  stream  having  followed  the  course  of 
the  Rhone ;  the  central,  that  of  the  Aar ;  and  the  eastern,  that  of 
the  two  great  rivers,  Reuss  and  Limmat.  The  non-intermixture  of 
these  groups  of  travelled  fragments,  except  near  their  confines,  was 
always  regarded  as  most  enigmatical  by  those  who  adopted  the  opinion 
of  Saussure,  that  they  were  all  whirled  along  by  a  rapid  current  of 
muddy  water  rushing  from  the  Alps. 

M.  Charpentier  first  suggested,  as  before  mentioned,  that  the  Swiss 
glaciers  once  reached  continuously  to  the  Jura,  and  conveyed  to  them 
these  erratics ;  but  at  the  same  time  he  conceived  that  the  Alps  were 
formerly  higher  than  now.  M.  Agassiz,  on  the  other  hand,  instead 
of  introducing  distinct  and  separate  glaciers,  suggested  that  the  whole 
valley  of  Switzerland  might  have  been  filled  with  ice,  and  that  one 
great  sheet  of  it  extended  from  the  Alps  to  the  Jura,  when  the  two 
chains  were  of  the  same  height  as  now  relatively  to  each  other.  Such 
an  hypothesis  labours  under  this  difficulty,  that  the  difference  of 
altitude,  when  distributed  over  a  space  of  50  miles,  gives  an  in- 
clination of  no  more  than  two  degrees,  or  far  less  than  that  of  any 
known  glaciers.  It  has,  however,  since  received  the  able  support  of 
Professor  James  Forbes,  in  his  excellent  work  on  the  Alps,  published 
in  1843. 

In  the  theory  which  I  formerly  advanced,  jointly  with  Mr.  Darwin  f, 

*  Archiac,  Hist.  desProgres,&c.  vol.  ii.  f  See  Elements  of  Geology,  2nd  ed. 
p.  249.  1841. 


CH.  XII.]  ERRATICS   OF   THE   JURA.  151 

it  was  suggested  that  the  erratics  may  have  been  transferred  by  float- 
ing ice  to  the  Jura,  at  the  time  when  the  greater  part  of  that  chain, 
and  the  whole  of  the  Swiss  valley  to  the  south,  was  under  the  sea. 
At  that  period  the  Alps  may  have  attained  only  half  their  present 
altitude,  and  may  yet  have  constituted  a  chain  as  lofty  as  the  Chilian 
Andes,  which,  in  a  latitude  corresponding  to  Switzerland,  now  send 
down  glaciers  to  the  head  of  every  sound,  from  which  icebergs, 
covered  with  blocks  of  granite,  are  floated  seaward.*  Opposite  that 
part  of  Chili  where  the  glaciers  abound  is  situated  the  island  of 
Chiloe,  100  miles  in  length,  with  a  breadth  of  30  miles,  running 
parallel  to  the  continent.  The  channel  which  separates  it  from  the 
main  land  is  of  considerable  depth,  and  25  miles  broad.  Parts  of  its 
surface,  like  the  adjacent  coast  of  Chili,  are  overspread  with  recent 
marine  shells,  showing  an  upheaval  of  the  land  during  a  very  modern 
period ;  and  beneath  these  shells  is  a  boulder  deposit,  in  which  Mr. 
Darwin  found  large  travelled  blocks.  One  group  of  fragments  were 
of  granite,  which  had  evidently  come  from  the  Andes,  while  in  an- 
other place  angular  blocks  of  syenite  were  met  with.  Their  arrange- 
ment may  have  been  due  to  successive  crops  of  icebergs  issuing  from 
different  sounds,  to  the  heads  of  which  glaciers  descend  from  the 
Andes.  These  icebergs,  taking  their  departure  year  after  year  from 
distinct  points,  may  have  been  stranded  repeatedly,  in  equally  distinct 
groups,  in  bays  or  creeks  of  Chiloe,  and  on  islets  off  the  coast ;  so  that 
the  stones  transported  by  them  might  hereafter  appear,  some  on  hills 
and  others  in  valleys,  should  that  country  and  the  bed  of  the  adjacent 
sea  be  ever  upheaved.  A  continuance  in  future  of  the  elevatory 
movement,  in  this  region  of  the  Andes  and  of  Chiloe,  might  cause 
the  former  chain  to  rival  the  Alps  in  altitude,  and  give  to  Chiloe  a 
height  equal  to  that  of  the  Jura.  The  same  rise  might  dry  up  the 
channel  between  Chiloe  and  the  main  land,  so  that  it  would  then 
represent  the  great  valley  of  Switzerland.  In  the  course  of  these 
changes,  all  parts  of  Chiloe  and  the  intervening  strait,  having  in  their 
turn  been  a  sea-shore,  may  have  been  polished  and  scratched  by 
coast-ice,  and  by  innumerable  icebergs  running  aground  and  grating 
on  the  bottom. 

If  we  apply  this  hypothesis  to  Switzerland  and  the  Jura,  we  are  by 
no  means  precluded  from  the  supposition  that,  in  proportion  as  the 
land  acquired  additional  height,  and  the  bed  of  the  sea  emerged,  the 
Jura  itself  may  have  had  its  glaciers  ;  and  those  existing  in  the  Alps, 
which  had  at  first  extended  to  the  sea,  may,  during  some  part  of  the 
period  of  upheaval,  have  been  prolonged  much  farther  into  the  valleys 
than  now.  At  a  later  period,  when  the  climate  grew  milder,  these 
glaciers  may  have  entirely  disappeared  from  the  Jura,  and  may  have 
receded  in  the  Alps  to  their  present  limits,  leaving  behind  them  in 
both  districts  those  moraines  which  now  attest  the  greater  extension 
of  the  ice  in  former  times.'j' 

*  Darwin's  Journal,  p.  283.  blocks  of  Mont  Blanc  were  translated  to 

f  More  recently   Sir  R.  Murchison,  the  Jura  when  the  intermediate  country 

having  revisited  the  Alps,  has  declared  was  under  water."  —  Paper  read  to  Geol. 

his    opinion  that  «« the  great    granitic  Soc.  London,  May  30.  1849. 

L  4 


152  METEORITES    IN    DRIFT.  [Cn.  XII. 

Meteorites  in  drift.  —  Before  concluding  my  remarks  on  the  north- 
ern drift  of  the  Old  World,  I  shall  refer  to  a  fact  recently  an- 
nounced, the  discovery  of  a  meteoric  stone  at  a  great  depth  in  the 
alluvium  of  Northern  Asia. 

Erman,  in  his  Archives  of  Russia  for  1841  (p.  314.),  cites  a  very 
circumstantial  account  drawn  up  by  a  Russian  miner  of  the  finding 
of  a  mass  of  meteoric  iron  in  the  auriferous  alluvium  of  the  Altai. 
Some  small  fragments  of  native  iron  were  first  met  with  in  the  gold- 
washings  of  Petropawlowsker  in  the  Mrassker  Circle ;  but  though 
they  attracted  attention,  it  was  supposed  that  they  must  have  been 
broken  off  from  the  tools  of  the  workmen.  At  length,  at  the  depth 
of  31  feet  5  inches  from  the  surface,  they  dug  out  a  piece  of  iron 
weighing  17|-  pounds,  of  a  steel-grey  colour,  somewhat  harder  than 
ordinary  iron,  and,  on  analysing  it,  found  it  to  consist  of  native  iron, 
with  a  small  proportion  of  nickel,  as  usual  in  meteoric  stones.  It 
was  buried  in  the  bottom  of  the  deposit  where  the  gravel  rested 
on  a  flaggy  limestone.  Much  brown  iron  ore,  as  well  as  gold,  occurs 
in  the  same  gravel,  which  appears  to  be  part  of  that  extensive  auri- 
ferous formation  in  which  the  bones  of  the  mammoth,  the  Rhinoceros 
tichorhinus.,  and  other  extinct  quadrupeds  abound.  No  sufficient  data 
are  supplied  to  enable  us  to  determine  whether  it  be  of  Post-Pliocene 
or  Newer  Pliocene  date. 

We  ought  not,  I  think,  to  feel  surprise  that  we  have  not  hitherto 
succeeded  in  detecting  the  signs  of  such  aerolites  in  older  rocks ;  for, 
besides  their  rarity  in  our  own  days,  those  which  fell  into  the  sea 
(and  it  is  with  marine  strata  that  geologists  have  usually  to  deal), 
being  chiefly  composed  of  native  iron,  would  rapidly  enter  into  new 
chemical  combinations,  the  water  and  mud  being  charged  with 
chloride  of  sodium  and  other  salts.  We  find  that  anchors,  cannon, 
and  other  cast-iron  implements  which  have  been  buried  for  a  few 
hundred  years  off  our  English  coast  have  decomposed  in  part  or  en- 
tirely, turning  the  sand  and  gravel  which  enclosed  them  into  a  con- 
glomerate, cemented  together  by  oxide  of  iron.  In  like  manner 
meteoric  iron,  although  its  rusting  would  be  somewhat  checked  by  the 
alloy  of  nickel,  could  scarcely  ever  fail  to  decompose  in  the  course  of 
thousands  of  years,  becoming  oxide,  sulphuret  or  carbonate  of  iron, 
and  its  origin  being  then  no  longer  distinguishable.  The  greater  the 
antiquity  of  rocks, — the  oftener  they  have  been  heated  and  cooled, 
permeated  by  gases  or  by  the  waters  of  the  sea,  the  atmosphere  or 
mineral  springs, — the  smaller  must  be  the  chance  of  meeting  with  a 
mass  of  native  iron  unaltered ;  but  the  preservation  of  the  ancient 
meteorite  of  the  Altai,  and  the  presence  of  nickel  in  these  curious 
bodies,  renders  the  recognition  of  them  in  deposits  of  remote  periods 
less  hopeless  than  we  might  have  anticipated. 


Cn.  XIII.]  NEWER   PLIOCENE    STRATA.  153 


CHAPTER  XIII. 

NEWER  PLIOCENE    STRATA  AND   CAVERN   DEPOSITS. 

Chronological  classification  of  Pleistocene  formations,  why  difficult— Freshwater 
deposits  in  valley  of  Thames  —  In  Norfolk  cliffs  —  In  Patagonia  —  Comparative 
longevity  of  species  in  the  mammalia  and  testacea  —  Fluvio-marine  crag  of 
Norwich — Newer  Pliocene  strata  of  Sicily  —  Limestone  of  great  thickness  and 
elevation — Alternation  of  marine  and  volcanic  formations — Proofs  of  slow 
accumulation — Great  geographical  changes  in  Sicily  since  the  living  fauna  and 
flora  began  to  exist — Osseous  breccias  and  cavern  deposits — Sicily — Kirkdale— 
Origin  of  stalactite — Australian  cave-breccias  —  Geographical  relationship  of  the 
provinces  of  living  vertebrata  and  those  of  the  fossil  species  of  the  Pliocene 
periods — Extinct  struthious  birds  of  New  Zealand  —  Teeth  of  fossil  quadrupeds. 

HAVING  in  the  last  chapter  treated  of  the  boulder  formation  and  its 
associated  freshwater  and  marine  strata  as  belonging  chiefly  to  the 
close  of  the  Newer  Pliocene  period,  we  may  now  proceed  to  other 
deposits  of  the  same  or  nearly  the  same  age.  It  should,  however,  be 
stated  that  it  is  difficult  to  draw  the  line  of  separation  between  these 
modern  formations,  especially  when  we  are  called  upon  to  compare 
deposits  of  marine  and  freshwater  origin,  or  these  again  with  the 
ossiferous  contents  of  caverns. 

If  as  often  as  the  carcasses  of  quadrupeds  were  buried  in  alluvium 
during  floods,  or  mired  in  swamps,  or  imbedded  in  lacustrine  strata, 
a  stream  of  lava  had  descended  and  preserved  the  alluvial  or  fresh- 
water deposits,  as  frequently  happened  in  Auvergne  (see  above, 
p.  80.),  keeping  them  free  from  intermixture  with  strata  subse- 
quently formed,  then  indeed  the  task  of  arranging  chronologically 
the  whole  series  of  mammaliferous  formations  might  have  been  easy, 
even  though  many  species  were  common  to  several  successive  groups. 
But  when  there  have  been  oscillations  in  the  levels  of  the  land,  ac- 
companied by  the  widening  and  deepening  of  valleys  at  more  than 
one  period,  —  when  the  same  surface  has  sometimes  been  submerged 
beneath  the  sea,  after  supporting  forests  and  land  quadrupeds,  and 
then  raised  again,  and  subject  during  each  change  of  level  to  sedi- 
mentary deposition  and  partial  denudation,  —and  when  the  drifting  of 
ice  by  marine  currents  or  by  rivers,  during  an  epoch  of  intense  cold, 
has  for  a  season  interfered  with  the  ordinary  mode  of  transport,  or 
with  the  geographical  range  of  species,  we  cannot  hope  speedily  to 
extricate  ourselves  from  the  confusion  in  which  the  classification  of 
these  Pleistocene  formations  is  involved. 

At  several  points  in  the  valley  of  the  Thames,  remnants  of  ancient 
fluviatile  deposits  occur,  which  may  differ  considerably  in  age,  al- 
though the  imbedded  land  and  freshwater  shells  in  each  are  of  recent 
species.  At  Brentford,  for  example,  the  bones  of  the  Siberian  Mam- 


154  DEPOSITS   IN   VALLEY   OF    THAMES.  [Cn.  XIII. 

moth,  or  Elephas  primigenius,  and  the  Rhinoceros  tichorhinus,  both 
of  them  quadrupeds  of  which  the  flesh  and  hair  have  been  found 
preserved  in  the  frozen  soil  of  Siberia,  occur  abundantly,  with  the 
bones  of  an  hippopotamus,  aurochs,  short-horned  ox,  red  deer,  rein- 
deer, and  great  cave-tiger  or  lion.*  A  similar  group  has  been  found 
fossil  at  Maidstone,  in  Kent,  and  other  places,  agreeing  in  general 
specifically  with  the  fossil  bones  detected  in  the  caverns  of  England. 
When  we  see  the  existing  rein-deer  and  an  extinct  hippopotamus  in 
the  same  fluviatile  loam,  we  are  tempted  to  indulge  our  imaginations 
in  speculating  on  the  climatal  conditions  which  could  have  enabled 
these  genera  to  coexist  in  the  same  region.  Wherever  there  is  a 
continuity  of  land  from  polar  to  temperate  and  equatorial  regions, 
there  will  always  be  points  where  the  southern  limit  of  an  arctic 
species  meets  the  northern  range  of  a  southern  species ;  and  if  one  or 
both  have  migratory  habits,  like  the  Bengal  tiger,  the  American  bison, 
the  musk  ox  and  others,  they  may  each  penetrate  mutually  far  into  the 
respective  provinces  of  the  other.  There  may  also  have  -been  several 
oscillations  of  temperature  during  the  periods  which  immediately 
preceded  and  followed  the  more  intense  cold  of  the  glacial  epoch. 

The  strata  bordering  the  left  bank  of  the  Thames  at  Grays 
Thurrock,  in  Essex,  are  probably  of  older  date  than  those  of  Brent- 
ford, although  the  associated  land  and  freshwater  shells  are  nearly 
all,  if  not  all,  identical  with  species  now  living.  Three  of  the  shells, 
however,  are  no  longer  inhabitants  of  Great  Britain  ;  namely,  Palu- 
dina  marginata  (fig.  117.  p.  133.),  now  living  in  France;  Unio 
littoralis  (fig.  29.  p.  28.),  now  inhabiting  the  Loire;  and  Cyrena 
consobrina  (fig.  26.  p.  28.).  The  last-mentioned  fossil  (a  recent 
Egyptian  shell  of  the  Nile)  is  very  abundant  at  Grays,  and  deserves 
notice,  because  the  genus  Cyrena  is  now  no  longer  European. 

The  rhinoceros  occurring  in  the  same  beds  (/?.  leptorhinus,  see 
fig.  136.  p.  167.)  is  of  a  different  species  from  that  of  Brentford 
above  mentioned,  and  the  accompanying  elephant  belongs  to  the 
variety  called  Elephas  meridionalis,  which,  according  to  MM.  Owen 
and  H.  von  Meyer,  two  high  authorities,  is  the  same  species  as  the 
Siberian  mammoth,  although  some  naturalists  regard  it  as  distinct. 
With  the  above  mammalia  is  also  found  the  Hippopotamus  major,  and 
what  is  most  remarkable  in  so  modern  and  northern  a  deposit,  a 
monkey,  called  by  Owen  Macacus  pliocenus. 

The  submerged  forest  already  alluded  to  (p.  137.)  as  underlying 
the  drift  at  the  base  of  the  cliffs  of  Norfolk  is  associated  with  a  bed 
of  lignite  and  loam,  in  which  a  great  number  of  fossil  bones  occur, 
apparently  of  the  same  group  as  that  of  Grays,  just  mentioned.  It 
has  sometimes  been  called  "  the  Elephant  bed."  One  portion  of  it, 
which  stretches  out  under  the  sea  at  Happisburgh,  was  overgrown 
in  1820  by  a  bank  of  recent  oysters,  and  there  the  fishermen  dredged 
up,  according  to  Woodward,  in  the  course  of  thirteen  years,  together 
with  the  oysters,  above  2000  mammoths'  grinders,  j  Another  portion 

*  Morris,  Geol.  Soc.  Proceed.,  1849.          f  Woodward's  Geology  of  Norfolk. 


CH.  XIII.]  FLUVIO-MARINE   NORWICH   CRAG.  155 

of  the  same  continuous  stratum  has  yielded  at  Bacton,  Cromer,  and 
other  places  on  the  coast,  the  bones  of  a  gigantic  beaver  ( Trogon- 
therium  Cuvierii,  Fischer),  as  well  as  the  ox,  horse,  and  deer,  and 
both  species  of  rhinoceros,  JR.  tichorhinus  and  R.  leptorhinus. 

In  studying  these  and  various  other  similar  assemblages  of  fossils, 
we  have  a  good  exemplification  of  the  more  rapid  rate  at  which  the 
mammiferouS  fauna,  as  compared  to  the  testaceous,  diverges  from  the 
recent  type  when  traced  backwards  in  time.  I  have  before  hinted, 
that  the  longevity  of  species  in  the  class  of  warm-blooded  quadrupeds 
is  not  so  great  as  in  that  of  the  mollusca ;  the  latter  having  probably 
more  capacity  for  enduring  those  changes  of  climate  and  other 
external  circumstances,  and  those  revolutions  in  the  organic  world, 
which  in  the  course  of  ages  occur  on  the  earth's  surface.  This 
phenomenon  is  by  no  means  confined  to  Europe,  for  Mr.  Darwin 
found  at  Bahia  Blanca,  in  South  America,  lat  39°  S.,  near  the  northern 
confines  of  Patagonia,  fossil  remains  of  the  extinct  mammiferous 
genera  Megatherium,  Megalonyx,  Toxodon,  and  others,  associated 
with  shells,  almost  all  of  species  already  ascertained  to  be  still  living 
in  the  contiguous  sea* ;  the  marine  mollusca,  as  well  as  those  of  rivers, 
lakes,  or  the  land,  having  died  out  more  slowly  than  the  terrestrial 
mammalia. 

I  alluded  before  (p.  131.)  to  certain  marine  strata  overlying  till 
near  Glasgow,  and  at  other  points  on  the  Clyde,  in  which  the 
shells  are  for  the  most  part  British,  with  an  intermixture  of  some 
arctic  species;  while  others,  about  a  tenth  of  the  whole,  are  sup- 
posed to  be  extinct.  This  formation  may  also  be  called  Newer 
Pliocene. 

Fluvio-marine  crag  of  Norwich.  —  At  several  places  within  five 
miles  of  Norwich,  on  both  banks  of  the  Tare,  beds  of  sand,  loam, 
and  gravel,  provincially  termed  "  crag,"  but  of  a  very  different  age 
from  the  Suffolk  Crag,  occur,  in  which  there  is  a  mixture  of  marine, 
land,  and  freshwater  shells,  with  ichthyolites  and  bones  of  mammalia. 
It  is  clear  that  these  beds  have  been  accumulated  at  the  bottom  of  the 
sea  near  the  mouth  of  a  river.  They  form  patches  of  variable  thick- 
ness, resting  on  white  chalk,  and  are  covered  by  a  dense  mass  of 
stratified  flint  gravel.  The  surface  of  the  chalk  is  often  perforated 
to  the  depth  of  several  inches  by  the  Pholas  crispata,  each  fossil  shell 
still  remaining  at  the  bottom  of  its  cylindrical  cavity,  now  filled  up 
with  loose  sand  which  has  fallen  from  the  incumbent  crag.  This 
species  of  Pholas  still  exists  and  drills  the  rocks  between  high  and 
low  water  on  the  British  coast.  The  most  common  shells  of  these 
strata,  such  as  Fusus  striatus,  Turritella  terebra,  Cardium  edule,  and 
Cyprina  islandica,  are  now  abundant  in  the  British  seas ;  but  with 
them  are  some  extinct  species,  such  as  Nucula  Cobboldice  (fig.  125.) 
and  Tellina  obliqua  (fig.  126.).  Natica  helicoides  (fig.  127.)  is  an 
example  of  a  species  formerly  known  only  as  fossil,  but  which  has 
now  been  found  living  in  our  seas. 

Among  the  accompanying  bones  of  mammalia  is  the  Mastodon 
*  Zool.  of  Beagle,  part  1.  pp.  9.  111. 


156 


NORWICH   CRAG  —  PLEISTOCENE.  [Cn.  XIII. 

Fig.  125.  Fig.  126.  Fig.  127- 


Nucula  CobboldicE. 


Tellina  obliqua. 


Natica  helicoides, 
Johnston. 


angustidens*  (see  fig.  135.  p.  166.),  a  portion  of  the  upper  jawbone  with 
a  tooth  having  been  found  by  Mr.  Wigham  at  Postwick,  near  Norwich. 
As  this  species  has  also  been  found  in  the  Red  Crag,  both  at  Button 
and  at  Felixstow,  and  had  hitherto  been  regarded  as  characteristic  of 
formations  older  than  the  Pleistocene,  it  may  possibly  have  been 
washed  out  of  the  Red  into  the  Norwich  Crag. 

Among  the  bones,  however,  respecting  the  authenticity  of  which 
there  seems  no  doubt,  may  be  mentioned  those  of  the  elephant,  horse, 
pig,  deer,  and  the  jaws  and  teeth  of  field  mice  (fig.  146.  p.  168.).  I  have 
seen  the  tusk  of  an  elephant  from  Bramerton  near  Norwich,  to  which 
many  serpula3  were  attached,  showing  that  it  had  lain  for  some  time 
at  the  bottom  of  the  sea  of  the  Norwich  Crag. 

At  Thorpe,  near  Aldborough,  and  at  Southwold,  in  Suffolk,  this 
fluvio-marine  formation  is  well  exposed  in  the  sea-cliffs,  consisting  of 
sand,  shingle,  loam,  and  laminated  clay.  Some  of  the  strata  there 
bear  the  marks  of  tranquil  deposition,  and  in  one  section  a  thickness 
of  40  feet  is  sometimes  exposed  to  view.  Some  of  the  lamelli- 
branchiate  shells  have  both  valves  united,  although  mixed  with  land 
and  freshwater  testacea,  and  with  the  bones  and  teeth  of  elephant, 
rhinoceros,  horse,  and  deer.  Captain  Alexander,  with  whom  I  ex- 
amined these  strata  in  1835,  showed  me  a  bed  rich  in  marine  shells, 
in  which  he  had  found  a  large  specimen  of  the  Fusus  striatus,  filled 
with  sand,  and  in  the  interior  of  which  was  the  tooth  of  a  horse. 

Among  the  freshwater  shells  I  obtained  the  Cyrena  consobrina 
(fig.  26.  p.  28.),  before  mentioned,  supposed  to  agree  with  a  species 
now  living  in  the  Nile. 

I  formerly  classed  the  Norwich  Crag  as  older  Pliocene,  conceiving 
that  more  than  a  third  of  the  fossil  testacea  were  extinct ;  but  there 
now  seems  good  reason  for  believing  that  several  of  the  rarer  shells 
obtained  from  these  strata  do  not  really  belong  to  a  contemporary 
fauna,  but  have  been  washed  out  of  the  older  beds  of  the  "  Red 
Crag ; "  while  other  species,  once  supposed  to  have  died  out,  have 
lately  been  met  with  living  in  the  British  seas.  According  to  Mr. 
Scarles  Wood,  the  total  number  of  marine  species  does  not  exceed 
seventy-six,  of  which  one  tenth  only  are  extinct.  Of  the  fourteen 
associated  freshwater  shells,  all  the  species  appear  to  be  living. 
Strata  containing  the  same  shells  as  those  near  Norwich  have  been 
found  by  Mr.  Bean,  at  Bridlington,  in  Yorkshire. 

Newer  Pliocene  strata  of  Sicily.  —  In  no  part  of  Europe  are  the 

*  Owen,  Brit.  Foss.  Mamm.  271.  Mastodon  kngirostris,  Kaup,  see  ibid. 


CH.  XIII.]  NEWER   PLIOCENE   STRATA   OF   SICILY.  157 

Newer  Pliocene  formations  seen  to  enter  so  largely  into  the  structure 
of  the  earth's  crust,  or  to  rise  to  such  heights  above  the  level  of  the 
sea,  as  in  Sicily.  They  cover  nearly  half  the  island,  and  near  its 
centre,  at  Castrogiovanni,  they  reach  an  elevation  of  3000  feet.  They 
consist  principally  of  two  divisions,  the  upper  calcareous,  and  the  lower 
argillaceous,  both  of  which  may  be  seen  at  Syracuse,  Girgenti,  and 
Castrogiovanni. 

According  to  Philippi,  to  whom  we  are  indebted  for  the  best 
account  of  the  tertiary  shells  of  this  island,  thirty-five  species  out 
of  one  hundred  and  twenty-four  obtained  from  the  beds  in  central 
Sicily,  are  extinct.  Of  the  remainder,  which  still  live,  five  species 
are  no  longer  inhabitants  of  the  Mediterranean.  When  I  visited 
Sicily  in  1828  I  estimated  the  proportion  of  living  species  as  some- 
what greater,  partly  because  I  confounded  with  the  tertiary  forma- 
tion of  central  Sicily  the  strata  at  the  base  of  -Etna,  and  some  other 
localities,  where  the  fossils  are  now  proved  to  agree  entirely  with  the 
present  Mediterranean  fauna. 

Philippi  came  to  the  conclusion,  that  in  Sicily  there  is  a  gradual 
passage  from  beds  containing  70  per  cent,  of  recent  shells,  to  those 
in  which  the  whole  of  the  fossils  are  identical  with  recent  species ; 
but  his  tables  appear  scarcely  to  bear  out  so  important  a  generaliza- 
tion, several  of  the  places  cited  by  him  in  confirmation  having  as  yet 
furnished  no  more  than  twenty  or  thirty  species  of  testacea.  The  Sici- 
lian beds  in  question  probably  belong  to  about  the  same  period  as  the 
Norwich  Crag,  although  a  geologist,  accustomed  to  see  nearly  all  the 
Pleistocene  formations  in  the  north  of  Europe  occupying  low  grounds 
and  very  incoherent  in  texture,  is  naturally  surprised  to  behold 
formations  of  the  same  age  so  solid  and  stony,  of  such  thickness, 
and  attaining  so  great  an  elevation  above  the  level  of  the  sea. 

The  upper  or  calcareous  member  of  this  group  in  Sicily  consists 
in  some  places  of  a  yellowish-white  stone,  like  the  calcaire  grossier 
of  Paris  ;  in  others,  of  a  rock  nearly  as  compact  as  marble.  Its  aggre- 
gate thickness  amounts  sometimes  to  700  or  800  feet.  It  usually 
occurs  in  regular  horizontal  beds,  and  is  occasionally  intersected  by 
deep  valleys,  such  as  those  of  Sortino  and  Pentalica,  in  which  are 
numerous  caverns.  The  fossils  are  in  every  stage  of  preservation, 
from  shells  retaining  portions  of  their  animal  matter  and  colour,  to 
others  which  are  mere  casts. 

The  limestone  passes  downwards  into  a  sandstone  and  conglome- 
rate, below  which  is  clay  and  blue  marl,  like  that  of  the  Subapennine 
hills,  from  which  perfect  shells  and  corals  may  be  disengaged.  The 
clay  sometimes  alternates  with  yellow  sand. 

South  of  the  plain  of  Catania  is  a  region  in  which  the  tertiary 
beds  are  intermixed  with  volcanic  matter,  which  has  been  for  the 
most  part  the  product  of  submarine  eruptions.  It  appears  that,  while 
the  clay,  sand,  and  yellow  limestone  before  mentioned  were  in  course 
of  deposition  at  the  bottom  of  the  sea,  volcanos  burst  out  beneath  the 
waters,  like  that  of  Graham  Island,  in  1831,  and  these  explosions  re- 
curred again  and  again  at  distant  intervals  of  time.  Volcanic  ashes 
and  sand  were  showered  down  and  spread  by  the  waves  and  currents 


158 


NEWER   PLIOCENE   STRATA   OF    SICILY.       [Cn.  XIII. 


so  as  to  form  strata  of  tuff,  which  are  found  intercalated  between  beds 
of  limestone  and  clay  containing  marine  shells,  the  thickness  of  the 
whole  mass  exceeding  2000  feet.  The  fissures  through  which  the 
lava  rose  may  be  seen  in  many  places  forming  what  are  called  dikes. 
In  part  of  the  region  above  alluded  to,  as,  for  example,  near  Len- 
tini,  a  conglomerate  occurs  in  which  I  observed  many  pebbles  of 
volcanic  rocks  covered  by  full-grown  serpulce.  We  may  explain  the 
origin  of  these  by  supposing  that  there  were  some  small  volcanic 
islands  which  may  have  been  destroyed  from  time  to  time  by  the 
waves,  as  Graham  Island  has  been  swept  away  since  1831.  The 
rounded  blocks  and  pebbles  of  solid  volcanic  matter,  after  being  rolled 
for  a  time  on  the  beach  of  such  temporary  islands,  were  carried  at 
length  into  some  tranquil  part  of  the  sea,  where  they  lay  for  years, 
while  the  marine  serpulce.  adhered  to  them,  their  shells  growing  and 
covering  their  surface,  as  they  are  seen  adhering  to  the  shell  figured 
in  p.  22.  Finally,  the  bed  of  pebbles  was  itself  covered  with  strata 
of  shelly  limestone.  At  Vizzini,  a  town  not  many  miles  distant  to 
the  S.  W.,  I  remarked  another  striking  proof  of  the  gradual  manner 
in  which  these  modern  rocks  were  formed,  and  the  long  intervals  of 
time  which  elapsed  between  the  pouring  out  of  distinct  sheets  of  lava, 
a  bed  of  oysters  no  less  than  20  feet  in  thickness  rests  upon  a  current 
of  basaltic  lava.  The  oysters  are  perfectly  identifiable  with  our 
common  eatable  species.  Upon  the  oyster  bed,  again,  is  superim- 
posed a  second  mass  of  lava,  together  with  tuff  or  peperino.  In  the 
midst  of  the  same  alternating  igneous  and  aqueous  formations  is  seen 
near  Galieri,  not  far  from  Vizzini,  a  horizontal  bed,  about  a  foot  and 
a  half  in  thickness,  composed  entirely  of  a  common  Mediterranean 
coral  (Caryophyllia  ccEspitosa,  Lam.).  These  corals  stand  erect  as 
they  grew ;  and,  after  being  traced  for  hundreds  of  yards,  are  again 
found  at  a  corresponding  height  on  the  opposite  side  of  the  valley. 

Fig.  128. 


Caryophyllia  ctzspitosa,  Lara.    (Cladncora  slellarta,  Milne  Edw.  and  Haitne.) 

a.  Stem  with  young  stem  growing  from  its  side. 
a*.  Young  stem  of  same  twice  magnified. 

b.  Portion  of  branch,  twice  magnified,  with  the  base  of  a  lateral  branch  ;  the  exterior 

ridges  of  the  main  branch  appearing  through  the  lamellae  of  the  lateral  one. 

c.  Transverse  section  of  same,  proving,  by  the  integrity  of  the  main  branch,  that  the 

lateral  one  did  not  originate  in  a  subdivision  of  the  animal. 

d.  A  branch,  having  at  its  base  another  laterally  united  to  it,  and  two  young  corals  at 

its  upper  part. 

e.  A  main  branch,  with  a  full-grown  lateral  one. 
/.  A  perfect  terminal  star. 


CH.  XIII.]      NEWER   PLIOCENE    STRATA   OF   SICILY.  159 

The  corals  are  usually  branched,  but  not  by  the  division  of  the 
animals  as  some  have  supposed,  but  by  the  attachment  of  young  indi- 
viduals to  the  sides  of  the  older,  ones  ;  and  we  must  understand  this 
mode  of  increase,  in  order  to  appreciate  the  time  which  was  required 
for  the  building  up  of  the  whole  bed  of  coral  during  the  growth  of 
many  successive  generations.* 

•Among  the  other  fossil  shells  met  with  in  these  Sicilian  strata, 
which  still  continue  to  abound  in  the  Mediterranean,  no  shell  is  more 
conspicuous,  from  its  size  and  frequent  occurrence,  than  the  great 
scallop,  Pecten  jacobfzus  (see  fig.  129.),  now  so  common  in  the  neigh- 
bouring seas.  We  see  this  shell  in  the  calcareous  beds  at  Palermo 
in  great  numbers,  in  the  limestone  at  Girgenti,  and  in  that  which 
alternates  with  volcanic  rocks  in  the  country  between  Syracuse  and 
Vizzini,  often  at  great  heights  above  the  sea. 

Fig.  129. 


Pecten  jacobtcus  ;  half  natural  size. 

The  more  we  reflect  on  the  preponderating  number  of  these  recent 
shells,  the  more  we  are  surprised  at  the  great  thickness,  solidity,  and 
height  above  the  sea  of  the  rocky  masses  in  which  they  are  entombed, 
and  the  vast  amount  of  geographical  change  which  has  taken  place 
since  their  origin.  It  must  be  remembered  that,  before  they  began 
to  emerge,  the  uppermost  strata  of  the  whole  must  have  been  de- 
posited under  water.  In  order,  therefore,  to  form  a  just  conception 
of  their  antiquity,  we  must  first  examine  singly  the  innumerable 
minute  parts  of  which  the  whole  is  made  up,  the  successive  beds  of 
shells,  corals,  volcanic  ashes,  conglomerates,  and  sheets  of  lava ;  and 
we  must  afterwards  contemplate  the  time  required  for  the  gradual 
upheaval  of  the  rocks,  and  the  excavation  of  the  valleys.  The  his- 
torical period  seems  scarcely  to  form  an  appreciable  unit  in  this'com- 

*  I  am  indebted  to  Mi*.  Lonsdale  for  the  details  above  given  respecting  the 
structure  of  this  coral. 


160  CAVE   BRECCIAS.  [Cn.  XIII. 

putation,  for  we  find  ancient  Greek  temples,  like  those  of  Girgenti 
(Agrigentum),  built  of  the  modern  limestone  of  which  we  are  speak- 
ing, and  resting  on  a  hill  composed  of  the  same  ;  the  site  having  re- 
mained to  all  appearance  unaltered  since  the  Greeks  first  colonised 
the  island. 

The  modern  geological  date  of  the  rocks  in  this  region  leads  to 
another  singular  and  unexpected  conclusion  —  namely,  that  the  fauna 
and  flora  of  a  large  part  of  Sicily  are  of  higher  antiquity  than  the 
country  itself,  having  not  only  flourished  before  the  lands  were  raised 
from  the  deep,  but  even  before  their  materials  were  brought  together 
beneath  the  waters.  The  chain  of  reasoning  which  conducts  us  to 
this  opinion  may  be  stated  in  a  few  words.  The  larger  part  of  the 
island  has  been  converted  from  sea  into  land  since  the  Mediterranean 
was  peopled  with  nearly  all  the  living  species  of  testacea  and  zoo- 
phytes. We  may  therefore  presume  that,  before  this  region  emerged, 
the  same  land  and  river  shells,  and  almost  all  the  same  animals  and 
plants,  were  in  existence  which  now  people  Sicily ;  for  the  terrestrial 
fauna  and  flora  of  this  island  are  precisely  the  same  as  that  of  other 
lands  surrounding  the  Mediterranean.  There  appear  to  be  no  peculiar 
or  indigenous  species,  and  those  which  are  now  established  there  must 
be  supposed  to  have  migrated  from  pre-existing  lands,  just  as  the 
plants  and  animals  of  the  Neapolitan  territory  have  colonized  Monte 
Nuovo,  since  that  volcanic  cone  was  thrown  up  in  the  sixteenth 
century. 

Such  conclusions  throw  a  new  light  on  the  adaptation  of  the  attri- 
butes and  migratory  habits  of  animals  and  plants  to  the  changes  which 
are  unceasingly  in  progress  in  the  physical  geography  of  the  globe. 
It  is  clear  that  the  duration  of  species  is  so  great,  that  they  are  des- 
tined to  outlive  many  important  revolutions  in  the  configuration  of 
the  earth's  surface ;  and  hence  those  innumerable  contrivances  for 
enabling  the  subjects  of  the  animal  and  vegetable  creation  to  extend 
their  range ;  the  inhabitants  of  the  land  being  often  carried  across 
the  ocean,  and  the  aquatic  tribes  over  great  continental  species.  It  is 
obviously  expedient  that  the  terrestrial  and  fluviatile  species  should 
not  only  be  fitted  for  the  rivers,  valleys,  plains,  and  mountains  which 
exist  at  the  era  of  their  creation,  but  for  others  that  are  destined  to 
be  formed  before  the  species  shall  become  extinct ;  and,  in  like  man- 
ner, the  marine  species  are  not  only  made  for  the  deep  and  shallow 
regions  of  the  ocean  existing  at  the  time  when  they  are  called  into 
being,  but  for  tracts  that  may  be  submerged  or  variously  altered  in 
depth  during  the  time  that  is  allotted  for  their  continuance  on  the 
globe. 

OSSEOUS  BBECCIAS  AND  DEPOSITS   IN   CAVES  OF  THE  PLIOCENE  PERIOD. 

Sicily.  —  Caverns  filled  with  marine  breccias,  at  the  base  of  ancient 
sea-cliffs,  have  been  already  mentioned  in  the  sixth  chapter;  and  it  was 
noticed,  respecting  the  cave  of  San  Giro,  near  Palermo  (p.  75.),  that 
upon  a  bed  of  sand  filled  with  sea-shells,  almost  all  of  recent  species, 


CH.  XIII. ]  KIRKDALE   CAVE.  161 

rests  a  breccia  (b,  fig.  93.  p.  75.),  composed  of  fragments  of  calcareous 
rock,  and  the  bones  of  animals.  In  the  sand  at  the  bottom  of  that  cave, 
Dr.  Philippi  found  about  forty-five  marine  shells,  all  clearly  identical 
with  recent  species,  except  two  or  three.  The  bones  in  the  incum- 
bent breccia  are  chiefly  those  of  the  mammoth  (E.  primigenius),  with 
some  belonging  to  an  hippopotamus,  distinct  from  the  recent  species, 
and  smaller  than  that  usually  found  fossil.  (See  fig.  137.  p.  167.) 
Several  species  of  deer  also,  and,  according  to  some  accounts,  the 
remains  of  a  bear,  were  discovered.  These  mammalia  are  probably 
referable  to  the  Post-Pliocene  period. 

The  Newer  Pliocene  tertiary  limestone  of  the  south  of  Sicily,  already 
described,  is  sometimes  full  of  caverns ;  and  the  student  will  at  once 
perceive  that  all  the  quadrupeds  of  which  the  remains  are  found  in 
the  stalactite  of  these  caverns,  being  of  later  origin  than  the  rocks, 
must  be  referable  to  the  close  of  the  tertiary  epoch,  if  not  of  still  later 
date.  The  situation  of  one  of  these  caves,  in  the  valley  of  Sortino, 
is  represented  in  the  annexed  section. 

Fig.  130. 


b  &A  Deposits  In  caves   \  containing  the  remains  of  quadrupeds  for  the  most  part  extinct. 

C.  Limestone,  containing  the  remains  of  shells,  of  which  between  70  and  80  per  cent,  are  recent. 

England. — In  the  cave  at  Kirkdale,  about  twenty-five  miles  N.N.E. 
of  York,  the  remains  of  about  300  hyaenas,  belonging  to  individuals 
of  every  age,  have  been  detected.  The  species  (Hyana  spelcea]  is 
extinct,  and  was  larger  than  the  fierce  Hycena  crocuta  of  South 
Africa,  which  it  most  resembled.  Dr.  Buckland,  after  carefully  ex- 
amining the  spot,  proved  that  the  Hyaenas  must  have  lived  there  ;  a 
fact  attested  by  the  quantity  of  their  dung,  which,  as  in  the  case  of 
the  living  hyaena,  is  of  nearly  the  same  composition  as  bone,  and 
almost  as  durable.  In  the  cave  were  found  the  remains  of  the  ox,  young 
elephant,  hippopotamus,  rhinoceros,  horse,  bear,  wolf,  hare,  water- 
rat,  and  several  birds.  All  the  bones  have  the  appearance  of  having 
been  broken  and  gnawed  by  the  teeth  of  the  hyaenas  ;  and  they  occur 
confusedly  mixed  in  loam  or  mud,  or  dispersed  through  a  crust  of 
stalagmite  which  covers  it.  In  these  and  many  other  cases  it  is  sup- 
posed that  portions  of  herbivorous  quadrupeds  have  been  dragged 
into  caverns  by  beasts  of  prey,  and  have  served  as  their  food,  an 
opinion  quite  consistent  with  the  known  habits  of  the  living  hyaena. 

No  less  than  thirty-seven  species  of  mammalia  are  enumerated  by 
Professor  Owen  as  having  been  discovered  in  the  caves  of  the  British 
islands,  of  which  eighteen  appear  to  be  extinct,  while  the  others  still 

M 


162  AUSTRALIAN    CAVERNS.  [Cn.  XIII. 

survive  in  Europe.  They  were  not  washed  to  the  spots  where  the 
fossils  now  occur  by  a  great  flood  ;  but  lived  and  died,  one  generation 
after  another,  in  the  places  where  they  lie  buried.  Among  other 
arguments  in  favour  of  this  conclusion  may  be  mentioned  the  great 
numbers  of  the  shed  antlers  of  deer  discovered  in  caves  and  in  fresh- 
water strata  throughout  England.* 

Examples  also  occur  of  fissures  into  which  animals  have  fallen  from 
time  to  time,  or  have  been  washed  in  from  above,  together  with  al- 
luvial matter  and  fragments  of  rock  detached  by  frost,  forming  a  mass 
which  may  be  united  into  a  bony  breccia  by  stalagmitic  infiltrations. 
Frequently  we  discover  a  long  suite  of  caverns  connected  by  narrow 
and  irregular  galleries,  which  hold  a  tortuous  course  through  the  in- 
terior of  mountains,  and  seem  to  have  served  as  the  subterranean 
channels  of  springs  and  engulphed  rivers.  Many  streams  in  the 
Morea  are  now  carrying  bones,  pebbles,  and  mud  into  underground 
passages  of  this  kind.  If,  at  some  future  period,  the  form  of  that 
country  should  be  wholly  altered  by  subterranean  movements  and 
new  valleys  shaped  out  by  denudation,  many  portions  of  the  former 
channels  of  these  engulphed  streams  may  communicate  with  the  sur- 
face, and  become  the  dens  of  wild  beasts,  or  the  recesses  to  which 
quadrupeds  retreat  to  die.  Certain  caves  of  France,  Germany,  and 
Belgium  may  have  passed  successively  through  these  different  con- 
ditions, and  in  their  last  state  may  have  remained  open  to  the  day 
for  several  tertiary  periods.  It  is  nevertheless  very  remarkable,  that 
on  the  continent  of  Europe,  as  in  England,  the  fossil  remains  of  mam- 
malia belong  almost  exclusively  to  those  of  the  Newer  Pliocene  and 
Post-Pliocene  periods,  and  not  to  the  Miocene  or  Eocene  epochs,  and 
when  they  are  accompanied  by  land  or  river  shells,  these  agree  in 
great  part,  or  entirely,  with  recent  species. 

As  the  preservation  of  the  fossil  bones  is  due  to  a  slow  and  constant 
supply  of  stalactite,  brought  into  the  caverns  by  water  dropping  from 
the  roof,  the  source  and  origin  of  this  deposit  has  been  a  subject  of 
curious  inquiry.  The  following  explanation  of  the  phenomenon  has 
been  recently  suggested  by  the  eminent  chemist  Liebig.  On  the 
surface  of  Franconia,  where  the  limestone  abounds  in  caverns,  is  a 
fertile  soil,  in  which  vegetable  matter  is  continually  decaying.  This 
mould  or  humus,  being  acted  on  by  moisture  and  air,  evolves  carbonic 
acid,  which  is  dissolved  by  rain.  The  rain  water,  thus  impregnated, 
permeates  the  porous  limestone,  dissolves  a  portion  of  it,  and  after- 
wards, when  the  excess  of  carbonic  acid  evaporates  in  the  caverns, 
parts  with  the  calcareous  matter,  and  forms  stalactite.  Such  facts 
seem  to  imply  that  the  date  of  the  emergence  of  the  district  was  very 
modern,  for  stalactite  could  not  begin  to  form  until  the  emergence  of 
the  cavernous  rock,  and  the  land  shells  and  land  animals  are  usually 
imbedded  in  the  lowest  part  of  the  stalactitic  deposit. 

Australian  cave-breccias. —  Ossiferous  breccias  are  not  confined  to 
Europe,  but  occur  in  all  parts  of  the  globe ;  and  those  lately  dis- 

*  Owen,  Brit.  Foss.  Mam.  xxri.,  and  Buckland,  Bel.  Dil.  19.  24. 


CH.  XIII.] 


FOSSILS   IN   AUSTRALIAN   CAVES. 


163 


covered  in  fissures  and  caverns  in  Australia  correspond  closely  in 
character  with  what  has  been  called  the  bony  breccia  of  the  Medi- 
terranean, in  which  the  fragments  of  bone  and  rock  are  firmly  bound 
together  by  a  red  ochreous  cement. 

Some  of  these  caves  have  been  examined  by  Sir  T.  Mitchell  in 
the  Wellington  Valley,  about  210  miles  west  of  Sidney,  on  the  river 
Bell,  one  of  the  principal  sources  of  the  Macquarie,  and  on  the 
Macquarie  itself.  The  caverns  often  branch  off  in  different  directions 
through  the  rock,  widening  and  contracting  their  dimensions,  and 
the  roofs  and  floors  are  covered  with  stalactite.  The  bones  are  often 
broken,  but  do  not  seem  to  be  water-worn.  In  some  places  they  lie 
imbedded  in  loose  earth,  but  they  are  usually  included  in  a  breccia. 

The  remains  found  most  abundantly  are  those  of  the  kangaroo,  ot 
which  there  are  four  species,  besides  which  the  genera  Hypsiprymnus, 
Phalangista,  Phascolomys,  and  Dasyurus,  occur.  There  are  also 
bones,  formerly  conjectured  by  some  osteologists  to  belong  to  the 
hippopotamus,  and  by  others  to  the  dugong,  but  which  are  now 
referred  by  Mr.  Owen  to  a  marsupial  genus,  allied  to  the  Wombat 

In  the  fossils  above  enumerated,  several  species  are  larger  than 

Pig.  131. 


Macropus  atlas,  Owen. 
a.  permanent  false  molar,  in  the  alveolus. 

the  largest  living  ones  of  the  same  genera  now  known  in  Australia. 
The  preceding  figure  of  the  right  side  of  a  lower  jaw  of  a  kangaroo 

Fig.  132. 


Lowest  jaw  of  largest  living  species  of  kangaroo. 

(Macropus  major.) 

M   2 


164  EXTINCT   FOSSIL    MAMMALIA.  [Cn.  XIII. 

(Macropus  atlas,  Owen)  will  at  once  be  seen  to  exceed  in  magnitude 
the  corresponding  part  of  the  largest  living  kangaroo,  which  is 
represented  in  fig.  132.  In  both  these  specimens  part  of  the 
substance  of  the  jaw  has  been  broken  open,  so  as  to  show  the 
permanent  false  molar  (a.  fig.  131.)  concealed  in  the  socket.  From 
the  fact  of  this  molar  not  having  been  cut,  we  learn  that  the 
individual  was  young,  and  had  not  shed  its  first  teeth.  In  fig.  133.  a 
Fi  133  front  tooth  of  the  same  species  of  kangaroo  is  re- 
presented. 

Whether  the  breccias,  above  alluded  to,  of  the  Wel- 
lington Valley,  appertain  strictly  to  the  Pliocene  period 
cannot  be  affirmed  with  certainty,  until  we  are  more 
thoroughly  acquainted  with  the  recent  quadrupeds  of 
the  same  district,  and  until  we  learn  what  species  of 
fossil  land-shells,  if  any,  are  buried  in  the  deposits  of 
the  same  caves. 

The  reader  will  observe  that  all  these  extinct  qua- 
drupeds of  Australia  belong  to  the  marsupial  family, 
or,  in  other  words,  that  they  are  referable  to  the  same 
peculiar  type  of  organization  which  now  distinguishes 
incisor  of  Ma-  the  Australian  mammalia  from  those  of  other  parts  of 
the  globe.  This  fact  is  one  of  many  pointing  to  a 
general  law  deducible  from  the  fossil  vertebrate  and  invertebrate 
animals  of  the  eras  immediately  antecedent  to  the  human,  namely, 
that  the  present  geographical  distribution  of  organic  forms  dates 
back  to  a  period  anterior  to  the  creation  of  existing  species;  in 
other  words,  the  limitation  of  particular  genera  or  families  of 
quadrupeds,  mollusca,  &c.,  to  certain  existing  provinces  of  land  and 
sea,  began  before  the  species  now  contemporary  with  man  had  been 
introduced  into  the  earth. 

Mr.  Owen,  in  his  excellent f(  History  of  British  Fossil  Mammals," 
has  called  attention  to  this  law,  remarking  that  the  fossil  quadrupeds 
of  Europe  and  Asia  differ  from  those  of  Australia  or  South  America. 
We  do  not  find,  for  example,  in  the  Europseo- Asiatic  province  fossil 
kangaroos  or  armadillos,  but  the  elephant,  rhinoceros,  horse,  bear, 
hysena,  beaver,  hare,  mole,  and  others,  which  still  characterize  the 
same  continent, 

In  like  manner,  in  the  Pampas  of  South  America  the  skeletons  of 
Megatherium,  Megalonyx,  Glyptodon,  Mylodon,  Toxodon,  Macrau- 
chenia,  and  other  extinct  forms,  are  analogous  to  the  living  sloth, 
armadillo,  cavy,  capybara,  and  llama.  The  fossil  quadrumana,  also 
associated  with  some  of  these  forms  in  the  Brazilian  caves,  belong  to 
the  Platyrrhine  family  of  monkeys,  now  peculiar  to  South  America. 
That  the  extinct  fauna  of  Buenos  Ayres  and  Brazil  was  very  modern 
has  been  shown  by  its  relation  to  deposits  of  marine  shells,  agreeing 
with  those  now  inhabiting  the  Atlantic  ;  and  when  in  Georgia  in 
1845,  I  ascertained  that  the  Megatherium,  Mylodon,  Harlanus  ame- 
ricanus  (Owen),  Equus  curvidens,  and  other  quadrupeds  allied  to  the 
Pampean  type,  were  posterior  in  date  to  beds  containing  marine  shells 
belonging  to  forty-five  recent  species  of  the  neighbouring  sea. 


CH.  XIII.]  EXTINCT   FOSSIL   MAMMALIA.  165 

There  are  indeed  some  cosmopolite  genera,  such  as  the  Mastodon 
(a  genus  of  the  elephant  family)  and  the  horse,  which  were  simul- 
taneously represented  by  different  fossil  species  in  Europe,  North 
America,  and  South  America ;  but  these  few  exceptions  can  by  no 
means  invalidate  the  rule  which  has  been  thus  expressed  by  Professor 
Owen,  that  in  "the  highest  organized  class  of  animals  the  same 
forms  were  restricted  to  the  same  great  provinces  at  the  Pliocene 
periods  as  they  are  at  the  present  day." 

However  modern,  in  a  geological  point  of  view,  we  may  consider 
the  Pleistocene  epoch,  it  is  evident  that  causes  more  general  and 
powerful  than  the  intervention  of  man  have  occasioned  the  disap- 
pearance of  the  ancient  fauna  from  so  many  extensive  regions.  Not 
a  few  of  the  species  had  a  wide  range ;  the  same  Megatherium,  for 
instance,  extended  from  Patagonia  and  the  river  Plata  in  South 
America,  between  latitudes  31°  and  39°  south,  to  corresponding  lati- 
tudes in  North  America,  the  same  animal  being  also  an  inhabitant  of 
the  intermediate  country  of  Brazil,  where  its  fossil  remains  have  been 
met  with  in  caves.  The  extinct  elephant,  likewise,  of  Georgia 
(Elephas  primigenius)  has  been  traced  in  a  fossil  state  northward 
from  the  river  Alatamaha,  in  lat.  33°  50'  N.  to  the  polar  regions, 
and  then  again  in  the  eastern  hemisphere  from  Siberia  to  the  south 
of  Europe.  If  it  be  objected  that,  notwithstanding  the  adaptation  of 
such  quadrupeds  to  a  variety  of  climates  and  geographical  conditions, 
their  great  size  exposed  them  to  extermination  by  the  first  hunter 
tribes,  we  may  observe  that  the  investigations  of  Lund  and  Clausen 
in  the  ossiferous  limestone  caves  of  Brazil  have  demonstrated  that 
these  large  mammalia  were  associated  with  a  great  many  smaller 
quadrupeds,  some  of  them  as  diminutive  as  field  mice,  which  hare 
all  died  out  together,  while  the  land-shells  formerly  their  contem- 
poraries still  continue  to  exist  in  the  same  countries.  As  we  may 
feel  assured  that  these  minute  quadrupeds  could  never  have  been 
extirpated  by  man,  especially  in  a  country  so  thinly  peopled  as  Brazil, 
so  we  may  conclude  that  all  the  species,  small  and  great,  have  been 
annihilated  one  after  the  other,  in  the  course  of  indefinite  ages,  by 
those  changes  of  circumstances  in  the  organic  and  inorganic  world 
which  are  always  in  progress,  and  are  capable  in  the  course  of  time 
of  greatly  modifying  the  physical  geography,  climate,  and  all  other 
conditions  on  which  the  continuance  upon  the  earth  of  any  living  being 
must  depend.* 

The  law  of  geographical  relationship  above  alluded  to,  between  the 
living  vertebrata  of  every  great  zoological  province  and  the  fossils 
of  the  period  immediately  antecedent,  even  where  the  fossil  species 
are  extinct,  is  by  no  means  confined  to  the  mammalia.  New  Zea- 
land, when  first  examined  by  Europeans,  was  found  to  contain  no  in- 
digenous land  quadrupeds,  no  kangaroos,  or  opossums,  like  Australia  ; 
but  a  wingless  bird  abounded  there,  the  smallest  living  representative 
of  the  ostrich  family,  called  the  Xivi,  by  the  natives  (Apteryx).  In 

*  See  Principles  of  Geology,  chaps,  xli.  to  xliv. 
M  3 


166 


TEETH    OF    FOSSIL    QUADRUPEDS. 


[Cn.  XIII. 


the  fossils  of  the  Post-Pliocene  and  Pleistocene  period  in  this  same 
island,  there  is  the  like  absence  of  kangaroos,  opossums,  wombats, 
and  the  rest ;  but  in  their  place  a  prodigious  number  of  well  preserved 
specimens  of  gigantic  birds  of  the  struthious  order,  called  by  Owen 
Dinornis  and  Palapteryx,  which  are  entombed  in  superficial  deposits. 
These  genera  comprehended  many  species,  some  of  which  were  4, 
some  7,  others  9,  and  others  1 1  feet  in  height !  It  seems  doubtful 
whether  any  contemporary  mammalia  shared  the  land  with  this  popu- 
lation of  gigantic  feathered  bipeds. 

To  those  who  have  never  studied  comparative  anatomy  it  may  seem 
scarcely  credible,  that  a  single  bone  taken  from  any  part  of  the  skeleton 
may  enable  a  skilful  osteologist  to  distinguish,  in  many  cases,  the 
genus,  and  sometimes  the  species,  of  quadruped  to  which  it  belonged. 
Although  few  geologists  can  aspire  to  such  knowledge,  which  must  be 
the  result  of  long  practice  and  study,  they  will  nevertheless  derive 
great  advantage  from  learning,  what  is  comparatively  an  easy  task,  to 
distinguish  the  principal  divisions  of  the  mammalia  by  the  forms  and 
characters  of  their  teeth.  The  annexed  figures,  all  taken  from  original 

a  Fig.  134.  b 


Elephas  primfgenius  (or  Mammoth) ;  molar  of  upper  jaw,  right  side ;  one  third  of  nat.  size. 
a.  grinding  surface.  b.  side  view. 

Fig.  135. 


Mastodon  angustidens  (Norwich  Crag,  Postwick,  also  found  in  Red  Crag,  see  p.  156.) ;  second  true 
molar,  left  side,  upper  jaw  ;  grinding  surface,  nat.  size.    (See  p.  156.) 


CH.  XIII. J  TEETH   OP    FOSSIL    MAMMALIA.  167 

specimens,  may  be  useful  in  assisting  the  student  to  recognize  the 
teeth  of  many  genera  most  frequently  found  fossil  in  the  Newer  Plio- 
cene and  Post-Pliocene  periods. 

Fig.  136.  Fig.  137.  Fig.  138. 


Rhinoceros. 


Rhinoceros  leptorhinus  ;  fos- 
sil from  freshwater  beds 
of  Grays,  Essex  (see  p. 
154.):  penultimate  molar, 
lower  jaw,  left  side;  two- 
thirds  of  nat.  size. 

Fig.  139. 


Hippopotamus. 

Hippopotamus;  from  cave 
near  Palermo  (see  p. 
160.)  ;  molar  tooth  ;  two- 
thirds  of  nat.  size. 


Sus  scrofa,  Lin.  (common 
pig) ;  from  shell-marl, 
Forfarshire;  posterior  mo- 
lar, lower  jaw,  nat.  size. 


Fig.  140. 


Horse. 

Equus  cabattus,  Lin.  (common  horse); 
from  the  shell-marl,  Forfarshire ;  se- 
cond molar,  lower  jaw. 

a.  grinding  surface,  two-thirds  nat.  size. 

b.  side  view  of  same,  half  nat.  size. 

Fig.  141. 


Tapir. 

Tapirus  Amerieanus ; 
recent;  third  molar, 
upper  jaw  ;  nat.  size. 


Fig.  142. 


a.  5.  Deer. 

Elk  (Cervus  alces,  Lin.);  re- 
cent ;  molar  of  upper  jaw. 

a.  grinding  surface. 

b.  lide  view;  two-thirds  of  nat. 

size. 


M  4 


c.  d.  Ox. 

Ox,  common,  from  shell-marl,  Forfar- 
shire ;  true  molar,  upper  jaw ;  two- 
thirds  nat.  size. 

c.  grinding  surface. 

d.  side  view ;  fangs  uppermost. 


168 


OLDER    PLIOCENE    FORMATIONS. 

Fig.  143.  Fig-  144. 


[Cn.  XIV 


Bear. 

a.  canine  tooth  or  tusk  of  bear  (  Ursta 

spel&us) ;  from  cave  near  Liege. 

b.  molar  of  left  side,  upper  jaw ;  one- 

third  of  nat.  size. 

Fig.  145. 


Tiger. 

c.  canine  tooth  of  tiger   (Felis  tigrit) ; 

recent. 

d.  outside  view  of  posterior  molar,  lowei 

jaw ;  one-third  of  nat.  size. 


Hyaena  tpehea  ,•  second  molar,  left 
side,  lower  jaw;  nat.  size.  Cave 
ofKirkdale.  (See  p.  161. 


Teeth  of  a  new  species  of  Arvicola  (field-mouse)  ;  from  the 

Norwich  Crag.    (See  p.  163.) 
a.  grinding  surface.  b.  side  view  of  same. 

c.  nat.  size  of  a  and  b. 

Fig.  147. 


fourth  molar,  rijrht  side,  lower  jaw.    Megatherium  ;  Georgia, 
U.  S. ;  one-third  nat.  size. 


b.  crown  of  same. 


CHAPTER  XIV. 

OLDER   PLIOCENE   AND   MIOCENE   FORMATIONS. 

Strata  of  Suffolk  termed  Red  and  Coralline  Crag — Fossils,  and  proportion  of  recent 
species — Depth  of  sea  and  climate — Reference  of  Suffolk  Crag  to  the  Older 
Pliocene  period — Migration  of  many  species  of  shells  southwards  during  the 
glacial  period  —  Fossil  whales — Antwerp  Crag  —  Subapennine  beds — Asti, 
Sienna,  Rome — Aralo-Caspian  formations — Miocene  formations — Faluns  of 
Touraine — Depth  of  sea  and  .littoral  character  of  fauna — Tropical  climate 
implied  by  the  testacea — Proportion  of  recent  species  of  shells — Faluns  more 
ancient  than  the  Suffolk  Crag — Miocene  strata  of  Bordeaux — of  the  Bolderberg 
in  Belgium — of  North  Germany — Vienna  Basin — Piedmont — Molasse  of 
Switzerland — Leaf-beds  of  Mull  in  Scotland  —  Older  Pliocene  and  Miocene 
formations  in  the  United  States  —  Sewalik  Hills  in  India. 

THE  older  Pliocene  strata,  which  next  claim  our  attention,  are  chiefly 
confined,  in  Great  Britain,  to  the  eastern  part  of  the  county  of  Suf- 


CH.  XIV.]  OLDER   PLIOCENE   FORMATIONS.  169 

folk,  where,  like  the  Norwich  beds  already  described,  they  are  called 
"  Crag,"  a  provincial  name  given  particularly  to  those  masses  of  shelly 
sand  which  have  been  used  from  very  ancient  times  in  agriculture,  to 
fertilize  soils  deficient  in  calcareous  matter.  The  relative  position  of 
the  "  Red  Crag  "  in  Essex  to  the  London  clay,  may  be  understood  by 
reference  to  the  accompanying  diagram  (fig.  148.). 

Fig.  148. 
Crag.  London  Clay.  Chalk. 


These  deposits,  according  to  Professor  E.  Forbes,  appear  by  their 
imbedded  shells  to  have  been  formed  in  a  sea  of  moderate  depth, 
usually  from  15  to  25  fathoms,  but  in  some  few  spots  perhaps  deeper. 
Yet  they  cannot  be  called  littoral,  because  the  fauna  is  such  as  may 
have  extended  40  or  50  miles  from  land. 

The  Suffolk  Crag  is  divisible  into  two  masses,  the  upper  of  which 
has  been  termed  the  Red,  and  the  lower  the  Coralline  Crag.*  The 
upper  deposit  consists  chiefly  of  quartzose  sand,  with  an  occasional 
intermixture  of  shells,  for  the  most  part  rolled,  and  sometimes  com- 
minuted. In  many  places  fossils  washed  out  of  older  tertiary  strata, 
especially  the  London  Clay,  are  met  with.  The  lower  or  coralline 
Crag  is  of  very  limited  extent,  ranging  over  an  area  about  20  miles 
in  length,  and  3  or  4  in  breadth,  between  the  rivers  Aide  and  Stour. 
It  is  generally  calcareous  and  marly — a  mass  of  shells,  bryozoaf, 
and  small  corals,  passing  occasionally  into  a  soft  building  stone.  At 
Sudbourn,  near  Orford,  where  it  assumes  this  character,  are  large 
quarries,  in  which  the  bottom  of  it  has  not  been  reached  at  the  depth 
of  50  feet.  At  some  places  in  the  neighbourhood,  the  softer  mass  is 
divided  by  thin  flags  of  hard  limestone,  and  corals  placed  in  the 
upright  position  in  which  they  grew. 

The  Red  Crag  is  distinguished  by  the  deep  ferruginous  or  ochreous 
colour  of  its  sands  and  fossils,  the  Coralline  by  its  white  colour.  Both 
formations  are  of  moderate  thickness ;  the  Red  Crag  rarely  exceeding 
40,  and  the  Coralline  seldom  amounting  to  20,  feet.  But  their  im- 
portance is  not  to  be  estimated  by  the  density  of  the  mass  of  strata 
or  its  geographical  extent,  but  by  the  extraordinary  richness  of  its 
organic  remains,  belonging  to  a  very  peculiar  type,  which  seems  to 
characterize  the  state  of  the  living  creation  in  the  north  of  Europe 
during  the  Older  Pliocene  era. 

For  a  large  collection  of  the  fish,  echinoderms,  shells,  bryozoa,  and 

*  See  paper  by  E.  Charlesworth,  Esq. ;  corals,  but  now  classed  by  naturalists  as 

London  and  Ed.  Phil.  Mag.  No.  xxxviii.  mollusca.     The  term  Polyzoum,    syno- 

p.  81.,  Aug.  1835.  nymous  with  Bryozoum,  was,  it  seems, 

f  Ehrenberg   proposed  in    1831   the  proposed  in  1 830,  or  the  year  before,  by 

term  Bryozoum,  or  "  Moss-animal,"  for  Mr.  J.  O.  Thompson,  but  is  less  generally 

the    molluscous    or    ascidian    form    of  adopted.     The  animals  of  the  Zoantkaria 

polyp,  characterized    by    haying    two  of  Milne  Edwards  and  Haime,  or  the  true 

openings  to  the  digestive  sack,  as  in  corals,  have  only  one  opening  to  the 

Eschara,  Flustra,  Retepora,  and   other  stomach, 
zoophytes    popularly   included    in    the 


170  SUFFOLK   CRAG.  [Cn.  XIV. 

corals  of  the  deposits  in  Suffolk,  we  are  indebted  to  the  labours  of 
Mr.  Searles  Wood.  Of  testacea  alone  he  has  obtained  230  species 
from  the  Red,  and  345  from  the  Coralline  Crag,  about  150 
being  common  to  each.  The  proportion  of  recent  species  in  the 
new  group  is  considered  by  Mr.  Wood  to  be  about  70  *  per  cent., 
and  that  in  the  older  or  Coralline  about  60.  When  I  examined  these 
shells  of  Suffolk  in  1835,  with  the  assistance  of  Dr.  Beck,  Mr. 
George  Sowerby,  Mr.  Searles  Wood,  and  other  eminent  concho- 
logists,  I  came  to  the  opinion  that  the  extinct  species  predomi- 
nated very  decidedly  in  number  over  the  living.  Recent  investi- 
gations, however,  have  thrown  much  new  light  on  the  conchology  of 
the  Arctic,  Scandinavian,  British,  and  Mediterranean  Seas.  Many 
of  the  species  formerly  known  only  as  fossils  of  the  Crag,  and 
supposed  to  have  died  out,  have  been  dredged  up  in  a  living  state 
from  depths  not  previously  explored.  Other  recent  species,  before 
regarded  as  distinct  from  the  nearest  allied  Crag  fossils,  have  been 
observed,  when  numerous  individuals  were  procured,  to  be  liable  to 
much  greater  variation,  both  in  size  and  form,  than  had  been  sus- 
pected, and  thus  have  been  identified.  Consequently,  the  Crag 
fauna  has  been  found  to  approach  much  more  nearly  to  the  recent 
fauna  of  the  Northern,  British,  and  Mediterranean  Seas  than  had  been 
imagined.  The  analogy  of  the  whole  group  of  testacea  to  the 
European  type  is  very  marked,  whether  we  refer  to  the  large  de- 
velopment of  certain  genera  in  number  of  species  or  to  their  size,  or 
to  the  suppression  or  feeble  representation  of  others.  The  indication 
also  afforded  by  the  entire  fauna  of  a  climate  not  much  warmer  than 
that  now  prevailing  in  corresponding  latitudes,  prepares  us  to  believe 
that  they  are  not  of  higher  antiquity  than  the  Older  Pliocene  era. 

The  position  of  the  Red  Crag  in  Essex  to  the  subjacent  London  clay 
and  chalk  has  been  already  pointed  out  (fig.  148.).  Whenever  the 
two  divisions  are  met  with  in  the  same  district,  the  Red  Crag  lies 
uppermost ;  and,  in  some  cases,  as  in  the  section  represented  in 
fig.  149.,  which  I  had  an  opportunity  of  seeing  exposed  to  view  in 
1839,  it  is  clear  that  the  older  or  Coralline  mass  b  had  suffered 
denudation,  before  the  newer  formation  a  was  thrown  down  upon  it. 

Fig.  149. 

Shottisham  g 

Creek.  Ramsholt.      -g 

pj 

C      1.1 

Section  near  Ipswich,  in  Suffolk. 
a.  Red  Crag.  b.  Coralline  Crag.  c.  London  Clay. 

At  D  there  is  not  only  a  distinct  cliff,  8  or  10  feet  high,  of  Coralline 
Crag,  running  in  a  direction  N.E.  and  S.W.,  against  which  the  red 
crag  abuts  with  its  horizontal  layers;  but  this  cliff  occasionally 
overhangs.  The  rock  composing  it  is  drilled  everywhere  by  Pho- 
lades,  the  holes  which  they  perforated  having  been  afterwards  filled 

*  See  Monograph  on  the  Crag  Mollusca.     Searles  Wood,  Paleont.  Soe.  1848. 


CH.  XIV.] 


OLDER   PLIOCENE   FORMATIONS. 


171 


with  sand  and  covered  over  when  the  newer  beds  were  thrown  down. 
As  the  older  formation  is  shown  by  its  fossils  to  have  accumulated 
in  a  deeper  sea  (15,  and  sometimes  25,  fathoms  deep  or  more),  there 
must  no  doubt  have  been  an  upheaval  of  the  sea-bottom  before  the 
cliff  here  alluded  to  was  shaped  out.  We  may  also  conclude  that  so 
great  an  amount  of  denudation  could  scarcely  take  place,  in  such  in- 
coherent materials,  without  many  of  the  fossils  of  the  inferior  beds 
becoming  mixed  up  with  the  overlying  crag,  so  that  considerable 
difficulty  must  be  occasionally  experienced  by  the  palaeontologists  in 
deciding  which  species  belong  severally  to  each  group. 

The  Red  Crag  being  formed  in  a  shallower  sea,  often  resembles  in 
structure  a  shifting  sand-bank,  its  layers  being  inclined  diagonally, 
and  the  planes  of  stratification  being  sometimes  directed  in  the  same 
quarry  to  the  four  cardinal  points  of  the  compass,  as  at  Butley.  That 
in  this  and  many  other  localities,  such  a  structure  is  not  deceptive 
or  due  to  any  subsequent  concretionary  rearrangement  of  particles, 
or  to  mere  lines  of  colour,  is  proved  by  each  bed  being  made  up  of 
flat  pieces  of  shell  which  lie  parallel  to  the  planes  of  the  smaller 
strata. 

Some  fossils,  which  are  very  abundant  in  the  Red  Crag,  have  never 
been  found  in  the  white  or  coralline  division ;  as,  for  example,  the 
Fusus  contrarius  (fig.  150.),  and  several  species  of  Murex  and 
Buccinum  (or  Nassa)  (see  figs.  151,  152.),  which  two  genera  seem 
wanting  in  the  lower  crag. 


Fig.  150. 


Fossils  characteristic  of  the  Red  Crag. 


Fig.  151. 


Fig.  152. 


Nassa  granulata. 
Fig.  153. 


Pusus  contrarius-  Murex  alveolatus.  Cyprcea  coccineUoides. 

Fig.  150.  half  nat.  size;  the  others  nat.  size. 

Among  the  bones  and  teeth  of  fishes  are  those  of  large  sharks 
(  Carcharodon),  and  a  gigantic  skate  of  the  extinct  genus  Myliobates, 
and  many  other  forms,  some  common  to  our  seas,  and  many  foreign 
to  them.  It  is  questionable,  however,  whether  all  these  can  really 
be  ascribed  to  the  era  of  the  Red  Crag.  Not  a  few  of  them  may 
possibly  have  been  derived  from  older  strata,  especially  from  those 
Upper  Eocene  formations  to  be  described  in  the  next  chapter,  which 
are  largely  developed  in  Belgium,  and  of  which  a  fragment  (the 
Hempstead  beds  of  Forbes)  escaped  denudation  in  England. 

The  distinctness  of  the  fossils  of  the  Coralline  from  those  of  the 


172 


FOSSILS   OF    THE    SUFFOLK   CRAG. 


[Cn.  XIV. 


Red  Crag,  arises  in  part  from  their  higher  antiquity,  and,  in  some 
degree,  from  a  difference  in  the  geographical  conditions  of  the 
submarine  bottom.  The  prolific  growth  of  corals,  echini,  and  a 
prodigious  variety  of  testacea  and  bryozoa,  implies  a  region  of 
deeper  and  more  tranquil  water;  whereas,  the  Red  Crag  may  have  been 
formed  afterwards  on  the  same  spot,  when  the  water  was  shallower. 
In  the  mean  time  the  climate  may  have  become  somewhat  cooler,  and 
some  of  the  zoophytes  which  flourished  in  the  first  period  may  have 
disappeared,  so  that  the  fauna  of  the  Red  Crag  acquired  a  character 
somewhat  more  nearly  resembling  that  of  our  northern  seas,  as  is 
implied  by  the  large  development  of  certain  sections  of  the  genera 
Fusus,  Buccinum,  Purpura,  and  Trochus,  proper  to  higher  latitudes, 
and  which  are  wanting  or  feebly  represented  in  the  inferior  crag. 

Some  of  the  corals  and  bryozoa  of  the  lower  crag  of  Suffolk  belong 
to  genera  unknown  in  the  living  creation,  and  of  a  very  peculiar 
structure  ;  as,  for  example,  that  represented  in  the  annexed  fig.  (154.)? 

Fig.  154. 

b 


Fascicularia  auranttum,  Milne  Edwards.    Family,  Tubuliporidcs,  of  same  author. 

Bryozoan  of  extinct  genus,  from  the  inferior  or  Coralline  Crag,  Suffolk. 
a.  exterior.  b.  vertical  section  of  interior.  c.  portion  of  exterior  magnified. 

d.  portion  of  interior  magnified,  showing  that  it  is  made  up  of  long,  thin,  straight  tubes,  united 
in  conical  bundles. 

which  is  one  of  several  species  having  a  globular  form.  The  great 
number  and  variety  of  these  zoophytes  probably  indicate  an  equable 
climate,  free  from  intense  cold  in  winter.  On  the  other  hand,  that 
the  heat  was  never  excessive  is  confirmed  by  the  prevalence  of 
northern  forms  among  the  testacea,  such  as  the  Glycimeris,  Cyprina, 
and  Astarte.  Of  the  genus  last  mentioned  (see  fig.  155.)  there  are 

Fig.  155. 


Astarte  (Crassina,  Lam.) ;  species  common  to  upper  and  lower  crag. 

Astarte  Omalii,  Lajonkaire ;  Syn.  A.  bipartita,  Sow.  Min.  Con.  T.  521.  f.  3.;  a  very  variable  species, 
most  characteristic  of  the  Coralline  Crag,  Suffolk. 


CH.  XIV.] 


OLDER   PLIOCENE   FORMATIONS. 


173 


about  fourteen  species,  many  of  them  being  rich  in  individuals ;  and 
there  is  an  absence  of  genera  peculiar  to  hot  climates,  such  as  Conus, 


Fig.  156. 


Fig.  157. 


Fig.  J58. 


Valuta  Lamberti,  young 
individ.,  Cor.  and  Ke 
Crag. 


Pyrula  reticulata,  Lam.; 
Coralline  Crag,  Ram- 
sholt, 


Temnechinus  excavatus, 
Forbes;  Temnopleurus 
excavatus,  Wood ;  Cor. 
Crag,  Ramsholt. 


Oliva,  Mitra,  Fasciolaria,  Crassatella,  and  others.  The  cowries 
(Cyprcea,  fig.  153.),  also,  are  small,  and  belong  to  a  section  (Trivia) 
now  inhabiting  the  colder  regions.  A  large  volute,  called  Valuta 
Lamberti  (fig.  156.),  may  seem  an  exception;  but  it  differs  in  form 
from  the  volutes  of  the  torrid  zone,  and  may,  like  the  living  Valuta 
Magellanica,  have  been  fitted  for  an  extra-tropical  climate. 

The  occurrence  of  a  species  of  Lingula  at  Sutton  (see  fig.  160.) 
is  worthy  of  remark,  as  these  Brachiopoda  seem  now  confined  to 
more  equatorial  latitudes ;  and  the  same  may  be  said  still  more 
decidedly  of  a  species  of  Pyrula,  supposed  by  Mr.  Wood  to  be 
identical  with  P.  reticulata  (fig.  157.),  now  living  in  the  Indian 
Ocean.  A  genus  also  of  echinoderms,  called  by  Professor  Forbes 
Temnechinus  (fig.  158.),  is  peculiar  to  the  Red  and  Coralline  Crag 
of  Suffolk.  The  only  species  now  living  occur  in  the  Indian  Ocean. 
Whether,  therefore,  we  may  incline  to  the  belief  that  the  mean  annual 
temperature  was  higher  or  lower  than  now,  we  may  at  least  infer 
that  the  climate  and  geographical  conditions  were  by  no  means  the 
same  at  the  period  of  the  Suffolk  Crag  as  those  which  now  prevail  in 
the  same  region. 

One  of  the  most  interesting  conclusions  deduced  from  a  careful 
comparison  of  the  shells  of  these  British  Older  Pliocene  strata 
and  the  fauna  of  our  present  seas,  has  been  pointed  out  by  Prof. 
E.  Forbes.  It  appears  that,  during  the  glacial  period,  a  period 
intermediate,  as  we  have  seen,  between  that  of  the  crag  and  our  own 
time,  many  shells,  previously  established  in  the  temperate  zone,  re- 
treated southwards  to  avoid  an  uncongenial  climate.  The  Professor 
has  given  a  list  of  fifty  shells  which  inhabited  the  British  seas  while 
the  Coralline  and  Red  Crag  were  forming,  and  which,  though  now 
living  in  our  seas,  are  all  wanting  in  the  Pleistocene  or  glacial 
deposits.  They  must  therefore,  after  their  migration  to  the  south, 
which  took  place  during  the  glacial  period,  have  made  their  way 
northwards  again.  In  corroboration  of  these  views,  it  is  stated  that 
all  these  fifty  species  occur  fossil  in  the  Newer  Pliocene  strata  of 


1 74  SUBAPENNINE    STRATA.  [Cn.  XIV. 

Sicily,  Southern  Italy,  and  the  Grecian  Archipelago,  where  they  may 
have  enjoyed,  during  the  era  of  floating  icebergs,  a  climate  resembling 
that  now  prevailing  in  higher  European  latitudes.* 

In  the  Red  Crag  at  Felixstow,  in  Suffolk,  Professor  Henslow  has 
found  the  ear-bones  of  one  or  more  species  of  cetacea,  which,  ac- 
cording to  Prof.  Owen,  are  the  remains  of  true  whales  of  the  family 
BalcenidcB  (fig.  159.).  Mr.  Wood  is  of  opinion  that  these  cetacea  may 
be  of  the  age  of  the  Red  Crag,  or  if  not  that  they  may  be  derived 
from  the  destruction  of  beds  of  Coralline  Crag. 

Antwerp. —  Strata  of  the  same  age  as  the  Red  and  Coralline  Crag  of 
Suffolk  have  been  long  known  in  the  country  round  Antwerp  and  on 
the  banks  of  the  Scheldt,  below  that  city.  More  than  200  species  of 

Fig.  159.  Fig.  160. 


Tympanic  bone  of  Baltena  emargfnata,  Lingula  Dumortieri,  Nyst ; 

Owen  ;  Red  Crag,  Felixtow.  Antwerp  Crag.     • 

testacea  have  been  collected  by  MM.  De  Wael,  Nyst,  and  others, 
of  which  two-thirds  have  been  identified  with  Suffolk  fossils  by  Mr. 
Wood.  Among  these  he  recognizes  Lingula  Dumortieri  of  Nyst 
(fig.  160.),  which  I  found  in  abundance  at  Antwerp  in  1851,  in  what 
is  called  by  M.  de  Wael  the  middle  crag.  More  than  half  of  the 
shells  of  this  Antwerp  deposit  agree  with  living  species,  and  these 
belong  in  great  part  to  the  fauna  of  our  northern  seas,  though  some 
Mediterranean  species  are  not  wanting.  I  also  met  with  numerous 
cetacean  bones  of  the  genera  Bal&noptera  and  Ziphius  in  the  same 
formation.  They  are  not  at  all  rolled,  as  if  washed  out  of  older  beds, 
and  I  infer  that  the  animals  to  which  they  belonged  once  coexisted 
in  the  same  sea  with  the  associated  mollusca.t 

Normandy. — I  observed  in  1840  a  small  patch  of  shells  corre- 
sponding to  those  of  the  Suffolk  Crag,  near  Valognes,  in  Normandy ; 
and  there  is  a  deposit  containing  similar  fossils  at  St.  George 
Bohon,  and  several  places  a  few  leagues  to  the  S.  of  Carentan,  in 
Normandy ;  but  they  have  never  been  traced  farther  southwards. 

Subapennine  strata.  —  The  Apennines,  it  is  well  known,  are  com- 
posed chiefly  of  secondary  rocks,  forming  a  chain  which  branches  off 
from  the  Ligurian  Alps  and  passes  down  the  middle  of  the  Italian 
peninsula.  At  the  foot  of  these  mountains,  on  the  side  both  of  the 
Adriatic  and  the  Mediterranean,  are  found  a  series  of  tertiary  strata, 
which  form,  for  the  most  part,  a  line  of  low  hills  occupying  the  space 
between  the  older  chain  and  the  sea.  Brocchi,  as  we  have  seen 
(p.  111.),  was  the  first  Italian  geologist  who  described  this  newer 
group  in  detail,  giving  it  the  name  of  the  Subapennines  ;  and  he 

*  E.  "Forbes,  Mem.  Geol.  Survey,  Gt.  f  Lyell  on  Belgian  Tertiaries,  Quart. 
Brit.  voL  I  386.  Journ.  Geol.  Soc.  1852,  p.  382. 


CH.  XIV.]  SUBAPENNINE    STRATA.  175 

classed  all  the  tertiary  strata  of  Italy,  from  Piedmont  to  Calabria,  as 
plrts  of  the  same  system.  Certain  mineral  characters,  he  observed, 
were  common  to  the  whole  ;  for  the  strata  consist  generally  of  light 
brown  or  blue  marl,  covered  by  yellow  calcareous  sand  and  gravel. 
There  are  also,  he  added,  some  species  of  fossil  shells  which  are  found 
in  these  deposits  throughout  the  whole  of  Italy. 

We  have  now,  however,  satisfactory  evidence  that  the  Subapennine 
beds  of  Brocchi,  although  chiefly  composed  of  Older  Pliocene  strata, 
belong  nevertheless,  in  part,  both  to  older  and  newer  members  of  the 
tertiary  series.  The  strata,  for  example,  of  the  Superga,  near  Turin, 
are  Miocene ;  those  of  Asti  and  Parma  Older  Pliocene,  as  is  the  blue 
marl  of  Sienna  ;  while  the  shells  of  the  incumbent  yellow  sand  of  the 
same  territory  approach  more  nearly  to  the  recent  fauna  of  the  Medi- 
terranean, and  may  be  Newer  Pliocene. 

The  greyish-brown  or  blue  marl  of  the  Subapennine  formation  is 
very  aluminous,  and  usually  contains  much  calcareous  matter  and 
scales  of  mica.  Near  Parma  it  attains  a  thickness  of  2000  feet,  and 
is  charged  throughout  with  marine  shells,  some  of  which  lived  in 
deep,  others  in  shallow  water,  while  a  few  belong  to  freshwater 
genera,  and  must  have  been  washed  in  by  rivers.  Among  these 
last  I  have  seen  the  common  Limnea  palustris  in  the  blue  marl, 
filled  with  small  marine  shells.  The  wood  and  leaves,  which  occa- 
sionally form  beds  of  lignite  in  the  same  deposit,  may  have  been 
carried  into  the  sea  by  similar  causes.  The  shells,  in  general,  are  soft 
when  first  taken  from  the  marl,  but  they  become  hard  when  dried. 
The  superficial  enamel  is  often  well  preserved,  and  many  snells 
retain  their  pearly  lustre,  part  of  their  external  colour,  and  even 
the  ligament  which  unites  the  valves.  No  shells  are  more  usually 
perfect  than  the  microscopic  foraminifera,  which  abound  near  Sienna, 
where  more  than  a  thousand  full-grown  individuals  may  be  sometimes 
poured  out  of  the  interior  of  a  single  univalve  of  moderate  dimensions. 

The  other  member  of  the  Subapennine  group,  the  yellow  sand  and 
conglomerate,  constitutes,  in  most  places,  a  border  formation  near  the 
junction  of  the  tertiary  and  secondary  rocks.  In  some  cases,  as  near 
the  town  of  Sienna,  we  see  sand  and  calcareous  gravel  resting  imme- 
diately on  the  Apennine  limestone,  without  the  intervention  of  any 
blue  marl.  Alternations  are  there  seen  of  beds  containing  fluviatile 
shells,  with  others  filled  exclusively  with  marine  species ;  and  I  ob- 
served oysters  attached  to  many  limestone  pebbles.  The  site  of 
Sienna  appears  to  have  been  a  point  where  a  river,  flowing  from  the 
Apennines,  entered  the  sea  when  the  tertiary  strata  were  formed. 

The  sand  passes  in  some  districts  into  a  calcareous  sandstone,  as 
at  San  Vignone.  Its  general  superposition  to  the  marl,  even  in  parts 
of  Italy  and  Sicily  where  the  date  of  its  origin  is  very  distinct,  may 
be  explained  if  we  consider  that  it  may  represent  the  deltas  of  rivers 
and  torrents,  which  gained  upon  the  bed  of  the  sea  where  blue  marl 
had  previously  been  deposited.  The  latter,  being  composed  of  the 
finer  and  more  transportable  mud,  would  be  conveyed  to  a  distance, 
and  first  occupy  the  bottom,  over  which  sand  and  pebbles  would 


176  MIOCENE    FORMATIONS.  [Cn.  XIV. 

afterwards  be  spread,  in  proportion  as  rivers  pushed  their  deltas 
farther  outwards.  In  some  large  tracts  of  yellow  sand  it  is  impoi- 
sible  to  detect  a  single  fossil,  while  in  other  places  they  occur  in 
profusion.  Occasionally  the  shells  are  silicified,  as  at  San  Yitale, 
near  Parma,  from  whence  I  saw  two  individuals  of  recent  species, 
one  freshwater  and  the  other  marine  (Limnea  palustris,  and  Cytherea 
concentrica,  Lam.),  both  perfectly  converted  into  flint. 

Rome. — The  seven  hills  of  Rome  are  composed  partly  of  marine 
tertiary  strata,  those  of  Monte  Mario,  for  example,  of  the  Older 
Pliocene  period,  and  partly  of  superimposed  volcanic  tuff,  on  the 
top  of  which  are  usually  cappings  of  a  fluviatile  and  lacustrine 
deposit.  Thus,  on  Mount  Aventine,  the  Vatican,  and  the  Capitol, 
we  find  beds  of  calcareous  tufa  with  incrusted  reeds,  and  recent  ter- 
restrial shells,  at  the  height  of  about  200  feet  above  the  alluvial  plain 
of  the  Tiber.  The  tusk  of  the  mammoth  has  been  procured  from 
this  formation,  but  the  shells  appear  to  be  all  of  living  species,  and 
must  have  been  imbedded  when  the  summit  of  the  Capitol  was  a 
marsh,  and  constituted  one  of  the  lowest  hollows  of  the  country  as  it 
then  existed.  It  is  not  without  interest  that  we  thus  discover  the 
extremely  recent  date  of  a  geological  event  which  preceded  an  his- 
torical era  so  remote  as  the  building  of  Rome. 

Aralo-  Caspian  formations. —  This  name  has  been  given  by  Sir  R. 
Murchison  and  M.  de  Verneuil  to  the  limestone  and  associated  sandy 
beds,  of  brackish- water  origin,  which  have  been  traced  over  a  very 
extensive  area  surrounding  the  Caspian,  Azof,  and  Aral  Seas,  and 
parts  of  the  northern  and  western  coasts  of  the  Black  Sea.  The 
fossil  shells  are  partly  freshwater,  as  Paludina,  Neritina,  &c.,  and  partly 
marine,  of  the  family  Cardiacice  and  My  till.  The  species  are  iden- 
tical, in  great  part,  with  those  now  inhabiting  the  Caspian  ;  and  when 
not  living,  they  are  analogous  to  forms  now  found  in  the  inland  seas 
of  Asia,  rather  than  to  oceanic  types.  The  limestone  rises  occa- 
sionally to  the  height  of  several  hundred  feet  above  the  sea,  and  is 
supposed  to  indicate  the  former  existence  of  a  vast  inland  sheet  of 
brackish  water  as  large  as  the  Mediterranean,  or  larger. 

The  proportion  of  recent  species  agreeing  with  the  fauna  of  the 
Caspian  is  so  considerable  as  to  leave  no  doubt  in  the  minds  of  the 
geologists  above  cited,  that  this  rock,  also  called  by  them  the  "  Steppe 
Limestone,"  belongs  to  the  Pliocene  period.* 

MIOCENE   FORMATIONS. 

Faluns  of  Touraine. —  The  strata  which  we  meet  with  next  in  the 
descending  order  are  those  called  by  many  geologists  "  Middle  Ter- 
tiary," and  for  which  in  1833  I  proposed  the  name  of  Miocene, 
selecting  the  faluns  of  the  valley  of  the  Loire  in  France  as  my 
example  or  type.  No  strata  contemporaneous  with  these  formations 
have  as  yet  been  met  with  in  the  British  Isles,  where  the  lower  crag 
of  Suffolk  is  the  deposit  nearest  in  age.  The  term  "faluns"  is 
given  provincially  by  French  agriculturists  to  shelly  sand  and  marl 
*  Geol.  of  Russia,  p.  279.  &c. 


CH.  XIV.]  FALUNS   OF    TOURAINE.  177 

spread  over  the  land  in  Touraine,  just  as  the  "crag"  was  formerly 
much  used  to  fertilize  the  soil  in  Suffolk.  Isolated  masses  of  such 
faluns  occur  from  near  the  mouth  of  the  Loire,  in  the  neighbourhood 
of  Nantes,  to  as  far  inland  as  a  district  south  of  Tours.  They  are 
also  found  at  Pontlevoy,  on  the  Cher,  about  70  miles  above  the 
junction  of  that  river  with  the  Loire,  and  30  miles  S.  E.  of  Tours. 
Deposits  of  the  same  age  also  appear  under  new  mineral  conditions 
near  the  towns  of  Dinan  and  Rennes,  in  Brittany.  I  have  visited  all 
the  localities  above  enumerated,  and  found  the  beds  on  the  Loire  to 
consist  principally  of  sand  and  marl,  in  which  are  shells  and  corals, 
some  entire,  some  rolled,  and  others  in  minute  fragments.  In  certain 
districts,  as  at  Doue,  in  the  department  of  Maine  and  Loire,  10  miles 
S.  W.  of  Saumur,  they  form  a  soft  building-stone,  chiefly  composed 
of  an  aggregate  of  broken  shells,  bryozoa,  corals,  and  echinoderms, 
united  by  a  calcareous  cement ;  the  whole  mass  being  very  like  the 
Coralline  Crag  near  Aldborough  and  Sudbourn  in  Suffolk.  The 
scattered  patches  of  faluns  are  of  slight  thickness,  rarely  exceeding 
50  feet ;  and  between  the  district  called  Sologne  and  the  sea  they 
repose  on  a  great  variety  of  older  rocks ;  being  seen  to  rest  succes- 
sively upon  gneiss,  clayslate,  various  secondary  formations,  including 
the  chalk ;  and,  lastly,  upon  the  upper  freshwater  limestone  of  the 
Parisian  tertiary  series,  which,  as  before  mentioned  (p.  111.),  stretches 
continuously  from  the  basin  of  the  Seine  to  that  of  the  Loire. 

At  some  points,  as  at  Louans,  south  of  Tours,  the  shells  are  stained 
of  a  ferruginous  colour,  not  unlike  that  of  the  Red  Crag  of  Suffolk. 
The  species  are,  for  the  most  part,  marine,  but  a  few  of  them  belong 
to  land  and  fluviatile  genera.  Among  the  former,  Helix  turonensis 
rig.  IGI.^  (fig.  45.  p.  30.)  is  the  most  abundant. 

Remains  of  terrestrial  quadrupeds  are  here 
and  there  intermixed,  belonging  to  the 
genera  Deinotherium  (fig.  161.),  Mastodon, 
Rhinoceros,  Hippopotamus,  Chasropota- 
mus,  Dichobune,  Deer,  and  others,  and 
these  are  accompanied  by  cetacea,  such 
as  the  Lamantine,  Morse,  Sea-calf,  and 
Dolphin,  all  of  extinct  species. 

Professor  E.  Forbes,  after  studying  the 
fossil  testacea  which  I  obtained  from  these 
beds,  informs  me  that  he  has  no  doubt 
Deinotherium  giganteum,  Kaup.  they  were  formed  partly  on  the  shore 
itself  at  the  level  of  low  water,  and  partly  at  very  moderate  depths, 
not  exceeding  ten  fathoms  below  that  level.  The  molluscous  fauna 
of  the  "  faluns  "  is  on  the  whole  much  more  littoral  than  that  of  the 
Red  and  Coralline  Crag  of  Suffolk,  and  implies  a  shallower  sea.  It  is, 
moreover,  contrasted  with  the  Suffolk  Crag  by  the  indications  it 
affords  of  an  extra-European  climate.  Thus  it  contains  seven  species 
of  Cyprcea,  some  larger  than  any  existing  cowry  of  the  Mediterranean, 
several  species  of  Oliva,  Ancillaria,  Mitra,  Terebra,  Pyrula,  Fas- 
ciolaria,  and  Conus.  Of  the  cones  there  are  no  less  than  eight 

N 


178     COMPARISON  OF  THE  CRAG  AND  FALUNS.   [Cn.  XIV. 

species,  some  very  large,  whereas  the  only  European  cone  is  of  di- 
minutive size.  The  genus  Nerita,  and  many  others,  are  also  repre- 
sented by  individuals  of  a  type  now  characteristic  of  equatorial  seas, 
and  wholly  unlike  any  Mediterranean  forms.  These  proofs  of  a  more 
elevated  temperature  seem  to  imply  the  higher  antiquity  of  the  faluns 
as  compared  with  the  Suffolk  Crag,  and  are  in  perfect  accordance 
with  the  fact  of  the  smaller  proportion  of  testacea  of  recent  species 
found  in  the  faluns. 

Out  of  290  species  of  shells,  collected  by  myself  in  1840  at 
Pontlevoy,  Louans,  Bossee,  and  other  villages  twenty  miles  south  of 
Tours ;  and  at  Savigne,  about  fifteen  miles  north-west  of  that  place  ; 
seventy-two  only  could  be  identified  with  recent  species,  which  is  in 
the  proportion  of  twenty-five  per  cent.  A  large  number  of  the  290 
species  are  common  to  all  the  localities,  those  peculiar  to  each  not 
being  more  numerous  than  we  might  expect  to  find  in  different  bays 
of  the  same  sea. 

The  total  number  of  testaceous  mollusca  from  the  faluns,  in  my 
possession,  is  302,  of  which  forty-five  only  were  found  by  Mr.  Wood 
to  be  common  to  the  Suffolk  Crag.  The  number  of  corals,  including 
bryozoa  and  zoantharia,  obtained  by  me  at  Doue,  and  other  localities 
before  adverted  to,  amounts  to  forty-three,  as  determined  by  Mr. 
Lonsdale,  of  which  seven  (one  of  them  a  zoantharian)  agree  spe- 
cifically with  those  of  the  Suffolk  Crag.  Only  one  has,  as  yet,  been 
identified  with  a  living  species.  But  it  is  difficult,  notwithstanding 
the  advances  recently  made  by  MM.  Dana,  Milne  Edwards,  Haime, 
and  Lonsdale,  to  institute  a  satisfactory  comparison  between  recent 
and  fossil  zoantharia  and  bryozoa.  Some  of  the  genera  occurring 
fossil  in  Touraine,  as  the  Astrea,  Dendrophyllia,  Lunulites,  have  not 
been  found  in  European  seas  north  of  the  Mediterranean;  nevertheless 
the  zoantharia  of  the  faluns  do  not  seem  to  indicate  on  the  whole  so 
warm  a  climate  as  would  be  inferred  from  the  shells. 

It  was  stated  that,  on  comparing  about  300  species  of  Touraine 
shells  with  about  450  from  the  Suffolk  Crag,  forty-five  only  were 
found  to  be  common  to  both,  which  is  in  the  proportion  of  only  fifteen 
per  cent.  The  same  small  amount  of  agreement  is  found  in  the 
corals  also.  I  formerly  endeavoured  to  reconcile  this  marked  dif- 
ference in  species  with  the  supposed  co-existence  of  the  two  faunas, 
by  imagining  them  to  have  severally  belonged  to  distinct  zoological 
provinces  or  two  seas,  the  one  opening  to  the  north,  and  the  other  to 
the  south,  with  a  barrier  of  land  between  them,  like  the  Isthmus  of 
Suez,  separating  the  Red  Sea  and  the  Mediterranean.  But  I  now 
abandon  that  idea  for  several  reasons  ;  among  others,  because  I  suc- 
ceeded in  1841  in  tracing  the  Crag  fauna  southwards  in  Normandy 
to  within  seventy  miles  of  the  Falunian  type,  near  Dinan,  yet  found 
that  both  assemblages  of  fossils  retained  their  distinctive  characters, 
showing  no  signs  of  any  blending  of  species  or  transition  of  climate. 

On  a  comparison  of  280  Mediterranean  shells  with  600  British 
species,  made  for  me  by  an  experienced  conchologist  in  1841,  160 
were  found  to  be  common  to  both  collections,  which  is  in  the  pro- 


Cn.  XIV.] 


SHELLS   IN   MIOCENE    STRATA. 


179 


portion  of  fifty-seven  per  cent.,  a  fourfold  greater  specific  resemblance 
than  between  the  seas  of  the  crag  and  the  faluns,  notwithstanding 
the  greater  geographical  distance  between  England  and  the  Mediter- 
ranean than  between  Suffolk  and  the  Loire.  The  principal  grounds, 
however,  for  referring  the  English  crag  to  the  Older  Pliocene  and  the 
French  faluns  to  the  Miocene  epochs,  consist  in  the  predominance  of 
fossil  shells  in  the  British  strata  identifiable  with  species,  not  only  still 
living,  but  which  are  now  inhabitants  of  neighbouring  seas,  while 
the  accompanying  extinct  species  are  of  genera  such  as  characterize 
Europe.  In  the  faluns,  on  the  contrary,  the  recent  species  are  in  a 
decided  minority ;  and  most  of  them  are  now  inhabitants  of  the  Medi- 
terranean, the  coast  of  Africa,  and  the  Indian  Ocean ;  in  a  word,  less 
northern  in  character  and  pointing  to  the  prevalence  of  a  warmer 
climate.  They  indicate  a  state  of  things  receding  farther  from  the 
present  condition  of  central  Europe  in  physical  geography  and  climate, 
and  doubtless,  therefore,  receding  farther  from  our  era  in  time. 
•  Bordeaux. — A  great  extent  of  country  between  the  Pyrenees  and 
the  Gironde  is  overspread  by  tertiary  deposits  of  various  ages  from 
the  Eocene  to  the  Pliocene.  Among  these,  especially  near  Saucats  in 
the  environs  of  Bordeaux,  and  at  Merignac  and  Bazas  in  the  same 
region,  are  sands  containing  marine  shells,  and  corals  of  the  type  of 
the  Touraine  faluns.* 

Belgium.  —  In  a  small  hill  or  ridge  called  the  Bolderberg,  which  I 
visited  in  1851,  situated  near  Hasselt,  about  forty  miles  E.  N.  E.  of 
Brussels,  strata  of  sand  and  gravel  occur,  to  which  M.  Dumont  first 
called  attention  as  appearing  to  constitute  a  northern  representative 
of  the  faluns  of  Touraine.  They  are  quite  distinct  in  their  fossils 
from  the  Antwerp  Crag  before  mentioned,  and  contain  shells  of  the 
genera  Oliva,  Conus,  Ancillaria,  Pleurotoma, 
and  Cancellaria  in  abundance.  The  most 
common  shell  is  an  Olive  (see  fig.  162.),  called 
by  Nyst  Oliva  Dufresnii,  Bast. ;  but  which  is 
undoubtedly,  as  M.  Bosquet  observes,  smaller 
and  shorter  than  the  Bordeaux  species,  f 

North  Germany.  —  We  learn  from  the  able 
treatise  published  by  M.  Beyrich,  in  1853,  that 

.          ^Q    f°SSil    *™™    abOV6    alluded  to>  which    is    SO 

a.  front  view;  b.  back  view,  meagrely  exhibited  in  the  Bolderberg,  is  rich 
in  species  in  other  localities  in  North  Germany,  as  in  Mecklenburg 
Liineburg,  the  Island  Sylt,  and  at  Bersenbriick  north  of  Osnabriick, 
in  Westphalia,  where  it  was  first  observed  by  F.  Romer.  It  is  also 
said  to  occur  at  Bocholt,  and  other  points  in  Westphalia;  on  the  borders 
of  Holland  ;  also  at  Crefeld  and  Dusseldorf.  Not  having  visited  these 
localities,  I  can  offer  no  opinion  as  to  the  agreement  in  age  of  the 
several  deposits  here  enumerated. 

*  See  a  Memoir  by  V.  Raulin,  1848:    seems  to  be  copied  from  that  given  by 
Bordeaux.  Basterot  of  the  Bordeaux  fossil. 

f  Lyell  on  Belgian  Tertiaries,  Quart.        %  Die  Conchylien  des  Norddeutschen 
Geol.  Journ.  1852,  p.  295.     Nyst's  figure     Tertiargebirge  :  Berlin,  1853. 

N  2 


Fig.  1G2. 


180  SHELLS   IN   MIOCENE    STRATA.  [Cn.  XIV. 

Vienna  basin.  —  In  South  Germany  the  general  resemblance  of 
the  shells  of  the  Vienna  tertiary  basin  with  those  of  the  faluns  of 
Touraine  has  long  been  acknowledged.  In  Dr.  Homes'  excellent  work, 
recently  commenced,  on  the  fossil  mollusca  of  that  formation,  we  see 
figures  of  many  shells  of  the  genus  Conus,  some  of  large  size,  clearly 
of  the  same  species  as  those  found  in  the  falunian  sands  of  Touraine. 
M.  Alcide  d'Orbigny  has  also  shown  that  the  foraminifera  of  the 
Vienna  basin  differ  alike  from  the  Eocene  and  Pliocene  species,  and 
agree  with  those  of  the  faluns,  so  far  as  the  latter  are  known.  Among 
the  Vienna  foraminifera,  the  genus  Amphistegina  (fig.  163.)  is  very 

Fig.  163. 


Amphistegina  Hauenna,  D'Orb.     Vienna,  miocene  strata. 

characteristic,  and  is  supposed  by  Archiac  to  take  the  same  place 
among  the  foraminifera  of  the  Miocene  era,  which  the  Nummulites 
occupy  in  the*Eocene  period. 

The  Vienna  basin  is  thought  by  some  geologists  to  comprise 
tertiary  strata  of  more  than  one  age,  the  lowest  strata  reached  in 
boring  Artesian  wells  being  older  than  the  faluns. 

Piedmont.  —  Switzerland.  —  To  the  same  Miocene  or  "falunian  " 
epoch,  we  may  refer  a  portion  of  the  strata  of  the  Hill  of  the  Superga 
near  Turin  in  Piedmont  *,  as  also  part  of  the  Molasse  of  Switzer- 
land, or  the  greenish  sand  which  fills  the  great  Swiss  valley  between 
the  Alps  and  the  Jura.  At  the  foot  of  the  Alps  it  usually  takes 
the  form  of  a  conglomerate  called  provincially  "  nagelflue,"  some- 
times attaining  the  truly  wonderful  thickness  of  6000  and  8000  feet, 
as  in  the  Rigi  near  Lucerne  and  in  the  Speer  near  Wesen.  The 
lower  portion  of  this  molasse  is  of  freshwater  origin. 

Scotland.  —  Isle  of  Mull.  —  In  the  sea-cliffs  forming  the  head- 
land of  Ardtun  on  the  west  coast  of  Mull,  in  the  Hebrides,  several 
bands  of  tertiary  strata  containing  leaves  of  dicotyledonous  plants 
were  discovered  in  185 1  by  the  Duke  of  Argyle.  f  From  his  descrip- 
tion it  appears  that  there  are  three  leaf-beds,  varying  in  thickness 
from  1^  to  2J  feet,  which  are  interstratified  with  volcanic  tuff  and 
trap,  the  whole  mass  being  about  130  feet  in  thickness.  A  sheet 
of  basalt  40  feet  thick  covers  the  whole  ;  and  another  columnar 
bed  of  the  same  rock  10  feet  thick  is  exposed  at  the  bottom  of 
the  cliff.  One  of  the  leaf-beds  consists  of  a  compressed  mass  of 
leaves  unaccompanied  by  any  stems,  as  if  they  had  been  blown  into 
a  marsh  where  a  species  of  Equisetum  grew,  of  which  the  remains 
are  plentifully  imbedded  in  clay. 

*  See  Sig.  Giov.  Micnelotti's  works.  f  Quart.  Geol.  Journ.  1851,  p.  89. 


Cu.  XIV.]          LEAF-BEDS   OF    MULL   IN    SCOTLAND.  181 

It  is  supposed  by  the  Duke  of  Argyle  that  this  formation  was 
accumulated  in  a  shallow  lake  or  marsh  in  the  neighbourhood  of 
a  volcano,  which  emitted  showers  of  ashes  and  streams  of  lava. 
The  tufaceous  envelope  of  the  fossils  may  have  fallen  into  the  lake 
from  the  air  as  volcanic  dust,  or  have  been  washed  down  into  it  as 
mud  from  the  adjoining  land.  The  deposit  is  decidedly  newer  than 
the  chalk,  for  chalk  flints  containing  cretaceous  fossils  were  detected 
by  the  Duke  in  the  principal  mass  of  volcanic  ashes  or  tutf'.* 

The  leaves  belong  to  species,  and  sometimes  even  to  families,  no 
longer  indigenous  in  the  British  Isles  ;  and  **  their  climatal  aspect," 
says  Prof.  E.  Forbes,  "is  more  mid-European  than  that  of  the  English 
Eocene  Flora.  They  also  resemble  some  of  the  Miocene  plants  of 
Croatia  described  by  Unger."  Some  of  them  appear  to  belong  to  a 
coniferous  tree,  possibly  a  yew  (Taxus)  ;  others,  still  more  abundant, 
to  a  plane  (Platanus),  having  the  same  outline  and  veining  well 
preserved.  No  accompanying  fossil  shells  have  been  met  with,  and 
there  seems  therefore  the  same  uncertainty  in  determining  whether 
these  beds  are  Upper  Eocene  or  Miocene,  which  we  experience  when 
we  endeavour  to  fix  the  age  of  many  continental  Brown-Coal  form- 
ations, those  of  Croatia  not  excepted. 

These  interesting  discoveries  in  Mull  naturally  raise  the  ques- 
tion, whether  the  basalt  of  Antrim  in  Ireland,  and  of  the  cele- 
brated Giant's  Causeway,  may  not  be  of  the  same  age.  For  in 
Antrim  the  basalt  overlies  the  chalk,  and  the  upper  mass  of  it 
covers  everywhere  a  bed  of  lignite  and  charcoal,  in  which  wood, 
with  the  fibre  well  preserved,  and  evidently  dicotyledonous,  is  pre- 
served.f  The  general  dearth  of  strata  in  the  British  Isles,  inter- 
mediate in  age  between  the  formation  of  the-  Eocene  and  Pliocene 
periods,  may  arise,  says  Prof.  Forbes,  from  the  extent  of  dry  land 
which  prevailed  in  the  vast  interval  of  time  alluded  to.  If  land  pre- 
dominated, the  only  monuments  we  are  likely  ever  to  find  of  Mio- 
cene date  are  those  of  lacustrine  and  volcanic  origin,  such  as  these 
Ardtun  beds  in  Mull,  or  the  lignites  and  associated  basalts  in 
Antrim.  On  the  flaules  of  Mont  Dor,  in  Auvergne,  I  have  seen 
leaf  beds  among  the  ancient  volcanic  tuffs  which  I  have  always 
supposed  to  be  of  Miocene  date.  Some  of  the  Brown  Coal  deposits 
of  Germany  are  believed  to  be  Miocene ;  others,  as  will  be  seen  in 
the  next  chapter,  are  Eocene,  Upper  or  Middle. 

Older  Pliocene  and  Miocene  formations  in  the  United  States.  — 
Between  the  Alleghany  mountains,  formed  of  older  rocks,  and  the 
Atlantic,  there  intervenes,  in  the  United  States,  a  low  region  occupied 
principally  by  beds  of  marl,  clay,  and  sand,  consisting  of  the  cretaceous 
and  tertiary  formations,  and  chiefly  of  the  latter.  The  general  eleva- 
tion of  this  plain  bordering  the  Atlantic  does  not  exceed  100  feet, 
although  it  is  sometimes  several  hundred  feet  high.  Its  width  in  the 
middle  and  southern  states  is  very  commonly  from  100  to  150  miles. 
It  consists,  in  the  South,  as  in  Georgia,  Alabama,  and  South  Carolina, 

*  Quart.  Geol.  Journ.  1851,  p.  90.  ,        f  Duke  of  Argyll,  ibid.  p.  101. 


182  PLIOCENE   AND   MIOCENE   FORMATIONS       J.CH.  XIV. 

almost  exclusively  of  Eocene  deposits  ;  but  in  North  Carolina,  Mary- 
land, Virginia,  Delaware,  more  modern  strata  predominate,  which, 
after  examining  them  in  1842,  I  supposed  to  be  of  the  age  of  the 
English  crag  and  Faluns  of  Touraine.*  If,  chronologically  speaking, 
they  can  be  truly  said  to  be  the  representatives  of  these  two  Euro- 
pean formations,  they  may  range  in  age  from  the  Older  Pliocene  to 
the  Miocene  epoch,  according  to  the  classification  of  European  strata 
adopted  in  this  chapter. 

The  proportion  of  fossil  shells  agreeing  with  recent,  out  of  147 
species  collected  by  me,  amounted  to  about  17  per  cent,  or  one-sixth 
of  the  whole ;  but  as  the  fossils  so  assimilated  were  almost  always  the 
same  as  species  now  living  in  the  neighbouring  Atlantic,  the  number 
may  hereafter  be  augmented,  when  the  recent  fauna  of  that  ocean  is 
better  known.  In  different  localities,  also,  the  proportion  of  recent 
species  varied  considerably. 

On  the  banks  of  the  James  River,  in  Virginia,  about  20  miles  below 
Richmond,  in  a  cliff  about  30  feet  high,  I  observed  yellow  and  white 
sands  overlying  an  Eocene  marl,  just  as  the  yellow  sands  of  the  crag  lie 
on  the  blue  London  clay  in  Suffolk  and  Essex  in  England.  In  the 
Virginian  sands,  we  find  a  profusion  of  an  Astarte  (A.  undulata, 
Conrad),  which  resembles  closely,  and  may  possibly  be  a  variety  of, 
one  of  the  commonest  fossils  of  the  Suffolk  Crag  (A.  bipartita) ;  the 
other  shells  also,  of  the  genera  Natica,  Fissurella,  Artemis,  Lucina, 
C/tama,  Pectunculus,  and  Pecten,  are  analogous  to  shells  both  of  the 
English  crag  and  French  faluns,  although  the  species  are  almost  all 
distinct.  Out  of  147  of  these  American  fossils  I  could  only  find  13 
species  common  to  Europe,  and  these  occur  partly  in  the  Suffolk 
Crag,  and  partly  in  the  faluns  of  Touraine ;  but  it  is  an  important 
characteristic  of  the  American  group,  that  it  not  only  contains  many 

Fig.  164.  Fig.  165. 


Fulgur  canaliculatus.    Maryland.  Fusus  quadricoslatus,  Say.    Maryland. 

peculiar  extinct  forms,  such  as  Fusus  quadricostatus,  Say  (see  fig. 
165.)  and  Venus  tridacnoides,  abundant  in  these  same  formations, 
but  also  some  shells  which,  like  Fulgur  carica  of  Say  and  F.  ca- 
naliculatus  (see  fig>  164.),  Calyptrcea  costata,  Venus  mercenaria, 

*  Proceed,  of  the  Geol.  Soc.  vol.  iv.  part  3.  1845,  p.  547. 


Cn.  XIV.]  IN   UNITED   STATES,   AND   IN   INDIA.  183 

Lam.,  Modiola  gla?idula,  Totten,  and  Pecten  magellanicus,  Lam.,  are 
recent  species,  yet  of  forms  now  confined  to  the  western  side  of  the 
Atlantic,  —  a  fact  implying  that  some  traces  of  the  beginning  of  the 
present  geographical  distribution  of  mollusca  date  back  to  a  period  as 
remote  as  that  of  the  Miocene  strata. 

Of  ten  species  of  zoophytes  which  I  procured  on  the  banks  of 
the  James  River,  one  was  formerly  supposed  by  Mr.  Lonsdale  to  be 
identical  with  a  fossil  from  the  faluns  of  Touraine,  but  this  species 

(see  fig.  166.)  proves  on  re-examination 
to  be  different,  and  to  agree  generically 
with  a  coral  now  living  on  the  coast  of 
the  United  States.  With  respect  to 
climate,  Mr.  Lonsdale  regards  these 
corals  as  indicating  a  temperature  ex- 
ceeding that  of  the  Mediterranean,  and 
the  shells  would  lead  to  similar  conclu- 
sions. Those  occurring  op  the  James 
River  are  in  the  37th  degree  of  N.  lati- 

Astransia  lineata,  Lonsdale.  ,  i  -i       i       -n  ini  •        i 

syn.  Inthophyiium  iineaium.       tude,  while  the  I1  rench  faluns  are  in  the 

Williamsburg,  Virginia.  ^^  .    ^    ^    forms  Qf  ^    American 

fossils  would  scarcely  imply  so  warm  a  climate  as  must  have  prevailed 
in  France  when  the  Miocene  strata  of  Touraine  originated. 

Among  the  remains  of  fish  in  these  Post-Eocene  strata  of  the  United 
States  are  several  large  teeth  of  the  shark  family,  not  distinguishable 
specifically  from  fossils  of  the  faluns  of  Touraine. 

India.  —  Sewalik  Hills.  —  The  freshwater  deposits  of  the  sub- 
Himalayan  or  Sewalik  Hills,  described  by  Dr.  Falconer  and  Captain 
Cautley,  belong  probably  to  some  part  of  the  Miocene  period,  although 
it  is  difficult  to  decide  this  question  until  the  accompanying  fresh- 
water and  land  shells  have  been  more  carefully  determined  and  com- 
pared with  fossils  of  other  tertiary  deposits.  The  strata  are  certainly 
newer  than  the  nummulitic  rocks  of  India,  and,  like  the  faluns  of 
Touraine,  they  contain  the  genera  Deinotherium  and  Mastodon,  with 
which  are  associated  no  less  than  seven  extinct  species  of  Elephants. 
The  presence  of  a  fossil  giraffe  and  hippopotamus,  genera  now  only 
living  in  Africa,  and  of  a  camel,  an  inhabitant  of  extensive  plains, 
implies  a  former  geographical  state  of  things  strongly  contrasted  with 
what  now  prevails  in  the  same  region.  A  species  of  Anoplotherium 
{A.  posterogenitum)  forms  a  link  between  this  fauna  and  that  of  the 
Eocene  period  ;  yet,  on  the  whole,  the  Sewalik  mammalia  have  a  more 
modern  aspect  than  those  of  the  Upper  Eocene,  so  many  being  re- 
ferable to  existing  genera,  whereas  almost  every  Eocene  genus  is  ex- 
tinct. Moreover,  the  sub-Himalayan  fauna  exhibits  a  great  develop- 
ment of  the  Ruminants,  an  order  so  feebly  represented  in  the  Eocene 
period.  In  addition  to  the  camel  and  giraffe  already  alluded  to,  we 
have  here  the  huge  Sivatherium,  a  ruminant  bigger  than  the  rhinoce- 
ros, and  provided  with  a  large  upper  lip,,  if  not  a  short  proboscis,  and 
having  two  pair  of  horns  resembling  those  of  antelopes.  The  number 
of  species  of  the  genus  Antelope  is  also  remarkable.  In  the  same  fauna 

N  4 


184  UPPER  EOCENE  FORMATIONS.        [Cn.  XV. 

appear  many  carnivorous  beasts,  often  belonging  to  existing  genera, 
and  several  species  of  monkey.  Among  the  reptiles  are  crocodiles, 
some  larger  than  any  now  living  ;  and  an  enormous  tortoise,  Testudo 
Atlas,  the  curved  shell  of  which  measured  twenty  feet  across. 


CHAPTER  XV. 

UPPER   EOCENE   FORMATIONS. 

(Lower  Miocene  of  many  authors.) 

Preliminary  remarks  on  classification,  and  on  the  line  of  separation  between 
Eocene  and  Miocene  strata  —  Whether  the  Limburg  and  contemporaneous 
formations  should  be  called  Upper  Eocene — Limburg  strata  in  Belgium — 
Strata  of  same  age  in  North  Germany  —  Mayence  basin — Brown  Coal  of 
Germany  —  Upper  Eocene  of  Hempstead  Hill,  Isle  of  Wight — Upper  Eocene 
of  France- — Lacustrine  strata  of  Auvergne — Indusial  limestone — Freshwater 
strata  of  the  Cantal — Its  resemblance  in  some  places  to  white  chalk  with  flints 
—  Proofs  of  gradual  deposition  —  Upper  Eocene  of  Bordeaux,  Aix-en-Provence, 
Malta,  &c.  —  Upper  Eocene  of  Nebraska,  United  States. 

Preliminary  remarks In  the  last  chapter  it  was  stated  that  as  yet 

we  know  of  no  marine  strata  in  the  British  Isles  contemporaneous  with 
the  faluns  of  Touraine,  or  those  shelly  deposits  of  the  valley  of  the 
Loire  which  I  selected  as  the  type  of  the  Miocene  period.  There 
have,  however,  been  recently  discovered  in  the  Isle  of  Wight  certain 
fluvio-marine  deposits,  which  many  continental  geologists  would  call 
*'  Lower  Miocene,"  the  "  faluns  "  being  termed  by  them  "  Upper  Mio- 
cene." A  few  preliminary  remarks  on  this  difference  of  nomencla- 
ture, bearing  as  it  does  on  questions  involving  the  first  principles 
of  classification,  will  be  necessary  before  I  treat  of  the  Upper  Eocene 
formations. 

The  marine  strata,  which  in  the  north  of  France  come  next  in  chro- 
nological order  to  the  "faluns," or  which  immediately  precede  them  in 
age,  are  the  sands  and  sandstones,  called  the  "  Gres  de  Fontainebleau," 
or  "  sables  marins  superieurs."  (See  General  Table,  p.  105.)  They 
constitute  the  uppermost  beds  of  the  Paris  basin,  and  are  overlaid  by 
a  freshwater  limestone  called  "  Calcaire  de  la  Beauce."  The  upper 
marine  sands  contain  no  fossil  shells  common  to  the  faluns,  or  ex- 
tremely few  species,  ;  and  no  shells  of  living  species,  or,  if  so,  they 
are  about  as  scarce  as  in  the  Middle  or  typical  Eocene  groups. 
In  consequence  of  this  distinctness  in  the  fossils,  and  for  other  reasons, 
presently  to  be  mentioned,  I  excluded  these  "  upper  sands"  from  the 
Miocene  period  in  former  editions  of  this  work,  availing  myself  of 
the  hiatus  between  the  Gres  de  Fontainebleau  and  the  faluns  to  draw 
a  line  of  separation  between  Eocene  and  Miocene.  In  support  of  this 
classification  I  pointed  out  the  fact  that  the  "  upper  marine  sands,"  or 


CH.  XT.]  EEMARKS    ON    CLASSIFICATION.  185 

Ores  de  Fontainebleau  of  the  Parisian  series,  with  their  characteristic 
shells,  extend  southwards  from  the  French  metropolis,  as  far  as 
Etampes,  which  is  within  seventy  miles  of  Pontlevoy,  near  Blois,  and 
not  more  than  100  miles  from  SaYigne,  near  Tours,  two  localities  where 
thefahmian  shells  are  very  abundant.  So  remarkable  a  difference 
between  the  species  of  the  valley  of  the  Loire  and  those  of  the  valley 
of  the  Seine  cannot  be  the  result  of  geographical  distribution  at  one 
and  the  same  former  era,  but  must  evidently  have  depended  on  a  dif- 
ference in  the  age  of  the  deposits.  It  marks  the  influence  of  Time,  and 
not  of  Space. 

Another  reason  which  induced  me  to  class  the  Gresde  Fontainebleau 
and  strata  of  the  same  age  with  the  older  series  rather  than  with  the 
newer,  was  the  decidedly  Eocene  aspect  of  the  testaceous  fauna,  and 
the  fact  that  a  certain  proportion  of  the  shells  of  the  "  upper  sands  " 
are  of  species  common  to  the  underlying  Parisian  strata. 

A  different  arrangement,  however,  was  adopted  by  MM.  Dufrenoy 
and  E.  de  Beaumont,  in  their  colouring  of  the  Government  Map  of 
France,  for  they  comprehended  in  their  Miocene  group,  not  only  the 
faluns  of  Touraine,  but  also  the  freshwater  "  calcaire  de  la  Beauce," 
and  the  marine  sands  and  sandstone  (Gres  de  Fontainebleau),  i.  e. 
all  the  tertiary  deposits  which  lie  above  the  gypseous  series  of  Mont- 
mar  tre,  a  formation  well  known  as  rich  in  extinct  mammalia,  first 
brought  to  light  by  the  genius  of  Cuvier.  M.  D'Archiac,  in  1839, 
followed  the  same  mode  of  classification,  dividing  what  he  termed 
"  Lower  "  from  his  "  Middle  tertiary  "  in  the  same  way.  M.  Deshayes, 
in  his  work  on  the  Fossil  Shells  of  the  Environs  of  Paris  (1824 — 
1837),  had  given  twenty-nine  species  as  belonging  to  the  upper  marine 
strata,  nearly  all  of  which  he  distinguished  specifically  from  shells  of 
the  Calcaire  Grossier,  although  he  regarded  them  as  characteristic 
of  the  same  fauna.  The  railway  cuttings  near  Etampes,  in  1849, 
enabled  M.  Hebert  to  raise  the  number  to  ninety,  and  he  first  pointed 
out  that  most  of  them  agreed  specifically  with  shells  of  Kleyn  Spawen, 
near  Maestricht,  in  Belgium,  and  with  those  of  Rupelmonde  and 
other  places  near  Antwerp.  These  Belgian  fossils  had  been  de- 
scribed by  MM.  Nyst,  De  Koninck,  and  Bosquet,  and  their  geological 
position  had  been  accurately  ascertained  by  M.  Dumont,  and  placed 
by  him  above  the  Brussels  tertiary  beds,  which  are  the  undoubted 
representatives  of  the  Calcaire  Grassier  of  Paris,  a  typical  Eocene 
group.  M.  de  Koninck,  about  the  same  time,  remarked  that  the 
Kleyn  Spawen,  or  "  Limburg "  fossils,  were  in  part  identical  with 
those  of  the  Mayence  tertiary  basin,  a  group  which  in  my  first 
editions  I  had  assigned  to  the  Miocene  period.  M.  Beyrich  more 
recently  (1850)  has  described  a  formation  of  the  same  age  as  that 
of  Kleyn  Spawen,  occurring  within  seven  miles  of  the  gates  of 
Berlin,  near  the  village  of  Hermsdorf ;  and  has  shown  that  about  a 
third  of  the  species  agreed  with  known  Belgian  shells  of  the  age  of 
the  Gres  de  Fontainebleau,  while  about  a  fifth  are  English  and 
French  Middle  Eocene  species. 

In  1851,  I  examined  with  care  the  Belgian  formations  at  Rupel- 


186  UPPER   EOCENE   FORMATIONS.  [Cn.  XV. 

monde  and  Boom,  near  Antwerp,  and  in  the  Limburg,  near  Maes- 
tricht,  and  was  able,  with  the  assistance  of  M.  Bosquet,  to  give 
a  table  of  no  less  than  201  species  of  shells  of  the  era  under  con- 
sideration. Of  these  more  than  a  third  proved  to  be  identical  with 
English  Eocene  testacea,  even  when  I  restricted  the  term  Eocene  to 
its  most  limited  sense,  extending  it  no  farther  upwards  than  the 
Middle  Eocene  or  nummulitic  formations.*  For  this  reason  I  called 
the  Limburg  or  Kleyn  Spawen  beds  Upper  Eocene,  giving  as  my 
reason  "  that  they  resembled  the  older  formations  in  their  fossils  as 
much  as  some  of  the  different  divisions  of  the  Eocene  series  in  France 
and  England  resemble  each  other;  as  much,  for  example,  as  the 
Barton  Clay  in  Hampshire  agrees  with  the  London  Clay  proper,  or 
the  Calcaire  Grossier  with  the  Soissonnais  sands  in  France." 

Subsequently,  in  the  winter  of  1852,  Professor  Edward  Forbes 
examined  near  Yarmouth,  in  the  Isle  of  Wight,  a  deposit  occupying 
a  very  limited  area,  but  about  170  feet  in  thickness,  which  he  first 
determined  to  be  of  the  same  age  as  the  Limburg  beds.  They  were 
found  to  be  in  comformable  position  with  the  other  tertiary  strata 
previously  known  in  that  island,  and  to  contain  abundantly  some  of 
the  most  characteristic  Kleyn  Spawen  fossils.  He  named  this 
deposit  "  the  Hempstead  series,"  and  classed  it  as  Upper  Eocene,  for 
reasons  similar  to  those  which  had  induced  me  so  to  name  the 
Limburg  beds  of  Belgium.  They  cannot  in  fact  be  separated  from 
the  subjacent  Eocene  strata  without  drawing  a  line  of  demarcation 
confessedly  arbitrary,  and  which  would  leave  a  great  many  of  the 
same  species  of  fossils  above  and  below  it.  So  complete,  indeed,  is 
the  passage  from  the  Bembridge  series  (an  equivalent  of  the  gypsum 
of  Montmartre,  and,  therefore,  an  acknowledged  Eocene  formation) 
into  the  Hempstead  beds,  that  Professor  Forbes  places  both  groups 
together  in  his  Upper  Eocene  division,  drawing  the  line  between 
Upper  and  Middle  Eocene  at  the  base  of  the  Bembridge  beds. 

In  opposition  to  this  view  two  recent  authorities,  who  in  the 
course  of  the  present  year  (1853)  have  written  on  the  tertiary 
formations  of  Germany,  M.  Beyrich,  before  cited  f,  and  Dr.  Sand- 
berger  },  contend  that  all  strata,  parallel  in  age  with  the  Limburg, 
should  be  termed  Lower  Miocene.  M.  Beyrich  affirms  that  if  the 
strata  of  the  Bolderberg  in  Belgium,  and  numerous  deposits  of  con- 
temporaneous date  of  Northern  Germany  already  enumerated 
(p.  179.),  be  of  the  age  of  the  "faluns,"  then  it  can  be  shown  that 
these  same  beds  have  so  many  fossils  in  common  with  the  Limburg 
strata,  that  the  latter  may  fairly  be  regarded  as  Miocene,  or  as  an 
older  deposit  of  the  same  great  period ;  and  he  goes  on  to  say  that, 
unless  we  are  prepared  to  allow  the  Eocene  division  to  absorb  all  the 
overlying  tertiary  formations,  we  must  begin  a  new  series  from  the 
base  of  the  Limburg  upwards,  calling  the  latter  Lower  Miocene. 

*  Quart.  Geol.  Journ.  1852,  vol.  viii.  J  Tiber  das  Mainzer  Tertiarbeckens, 
p.  322.  &c.:  Wiesbaden,  1853. 

f  Die  Conchylien   des  Norddeutsch. 
Tertiargeb.:  Berlin,  1853. 


Cn.XV.]     SEPARATION  OF  EOCENE  AND  MIOCENE  STRATA.    187 

Dr.  Sandberger  divides  the  strata  of  the  Mayence  basin  into  two 
sections,  an  older  and  a  newer,  the  former  confessedly  the  equivalent 
of  the  Liniburg  (or  Hempstead)  beds,  while  in  the  upper  he  finds 
some  fossil  remains,  which  appear  to  him  to  have  a  more  modern 
character.  But  when  we  separate  from  this  higher  division  the 
sands  of  Eppelsheim,  containing  bones  of  Deinotherium  and  Mastodon 
longirostris,  which  are  most  probably  of  falunian  age,  the  rest  of  his 
upper  series  may  be  as  old  as  the  Limburg  beds,  though,  for  want  of 
good  sections,  there  is  much  obscurity  in  regard  to  the  grouping  of 
the  beds.  Dr.  Sandberger,  however,  gives  a  list  of  twelve  shells,  be- 
sides some  teeth  of  fish  and  other  fossils,  which  are  common  to  the 
Mayence  basin  and  the  Hesse-Cassel  sands.  Now  the  latter  were 
classed  as  Subapennine  or  Pliocene  by  Philippi,  and,  although  we 
have  as  yet  no  sufficient  data  for  determining  their  true  age,  appear 
clearly  to  belong  to  a  more  modern  fauna  than  that  of  the  Mayence 
basin.  If  such  a  relationship  could  be  established  between  the  two 
as  to  indicate  a  passage  from  the  Hesse-Cassel  fauna  to  that  of  the 
Mayence  beds,  this  fact  would  doubtless  go  some  way  towards 
bearing  out  the  views  of  the  author. 

The  reader  has  probably  by  this  time  begun  to  perceive  that  one 
cause  of  embarrassment,  experienced  in  the  classification  of  these 
tertiary  formations,  arises  from  the  discovery  of  several  missing 
links  in  the  chain  of  historical  records.  I  may  remind  him  that  for 
more  than  twenty  years  I  have  advocated  in  the  Principles  of 
Geology  the  doctrine  that  there  has  been  a  continual  coming  in  of 
new  species,  and  dying  out  of  old  ones,  and  a  gradual  change  in  the 
physical  geography  and  climate  of  the  earth,  and  not  such  a  reitera- 
tion of  sudden  revolutions  in  the  animate  and  inanimate  worlds,  as 
was  once  insisted  upon  by  many  English  geologists  of  note,  and 
is  still  maintained  by  not  a  few  of  the  most  distinguished  continental 
writers.  When,  therefore,  I  proposed  in  1833  the  term  Miocene  for 
the  faluns  of  Touraine,  the  fossil  shells  of  which,  according  to  the 
determination  of  M.  Deshayes,  contained  an  admixture  of  about  seven- 
teen in  the  hundred  of  recent  species,  I  foretold  that  from  time  to  time 
new  sets  of  strata  would  come  to  light,  and  require  to  be  intercalated 
between  those  already  described,  and  in  that  case  that  the  fossils 
of  newly-found  beds  would  "  deviate  from  the  normal  types  first 
selected,  and  approximate  more  and  more  to  the  types  of  the  ante- 
cedent or  subsequent  epochs."  According  to  this  view,  it  was 
obvious  from  the  first  that  the  oldest  Miocene  records,  whenever 
they  were  detected,  would  not  be  easily  distinguishable  from  the 
youngest  members  of  the  Eocene  series,  especially  in  the  proportion 
of  the  living  to  the  extinct  species  of  fossil  shells.  The  importance, 
indeed,  of  the  latter  test  must  diminish  rapidly  the  more  we  recede 
from  the  Pliocene  and  approach  the  Miocene,  and  still  more  the 
Eocene  formations,  although  it  is  never  without  its  value,  and  often 
furnishes  the  only  common  standard  of  comparison  between  strata  of 
very  distant  countries. 

I  make  these  allusions  to  show  that  I  am  by  no  means  unprepared 


188  EOCENE   AND   MIOCENE   STRATA.  [Cn.  XV. 

for  the  discovery  of  gradations  from  Miocene  to  Eocene,  and  for  the 
probable  necessity  of  including  hereafter  in  the  Miocene  series 
some  fossiliferous  groups  which  may  diverge  in  their  characters  from 
the  standard  first  set  up,  or  from  the  type  of  the  faluns  of  Tou- 
raine.  But  I  have  seen,  as  yet,  no  sufficient  evidence  that  such  a 
passage,  as  is  here  spoken  of,  has  been  made  out.  The  limits  of  the 
Eocene  series  have  been  extended,  without  as  yet  filling  up  the  gap 
between  that  series  and  the  faluns  of  Touraine.  I  am  desirous  at  the 
same  time  to  explain,  that  the  important  point  now  at  issue  is  not 
simply  one  of  nomenclature.  The  difficulty  is  the  same,  whether  we 
use  the  terms  Lower  and  Middle  Tertiary,  or  Eocene  and  Miocene. 
To  one  or  other  of  the  periods  so  named  we  must  refer  the  Lirnburg 
and  Hempstead  beds,  and  the  sands  of  the  Forest  of  Fontainebleau. 
Can  we,  without  doing  violence  to  paleontological  principles,  refer 
all  these  to  the  same  period  as  the  faluns  of  Touraine  ?  If  so,  it  would 
be  immaterial  whether  we  called  them  Middle  Tertiary,  Miocene  or 
"  Falunian,"  or  by  any  other  general  name.  The  question  is,  whether, 
in  the  present  state  of  our  information,  the  mass  of  characteristic  fos- 
sils of  the  groups  alluded  to  resemble  more  nearly  the  Eocene  or  the 
Falunian.  I  adhere  at  present  to  the  nomenclature  formerly  adopted 
by  me  for  strata  described  in  this  chapter,  calling  them  Upper  Eocene 
—not  because  of  the  small  number  of  living  species  of  shells  found 
in  them,  although  this  is  certainly  one  point  of  agreement  between 
them  and  the  "nummulitic"  Eocene  beds,  but  because  of  the  aspect  of 
the  whole  fauna,  which  seems  to  me  to  be  Eocene  rather  than  Fa- 
lunian. Among  other  illustrations  of  this  affinity,  I  may  refer 
the  reader  to  the  numerous  and  excellent  figures  of  species  of  the 
genus  Valuta  given  by  M.  Beyrich  from  the  Limburg  beds  of  North 
Germany  —  forms  strikingly  characteristic  of  the  Barton  clay  in 
Hampshire,  a  regular  member  of  the  Middle  Eocene  group.  The 
faluns  are  devoid  of  such  forms.  Until,  therefore,  the  time  arrives 
when  the  break  between  the  Limburg  beds  and  the  faluns  has  dis- 
appeared more  completely,  it  appears  to  me  safer  to  include  the 
Limburg  and  all  contemporaneous  formations  in  the  Eocene. 

At  the  same  time  I  have  drawn  the  line  between  Middle  and  Upper 
Eocene,  as  in  former  editions,  excluding  from  the  latter  the  Bembridge 
beds  of  the  Isle  of  Wight,  or  the  gypseous  series  of  Montmartre.  A 
preference  is  given  to  this  last  method,  simply  for  convenience 
sake,  in  order  that  the  Upper  Eocene  of  this  work  may  coincide 
exactly  with  the  strata  classed  by  so  many  distinguished  geologists 
as  Lower  Miocene.  I  am  bound,  however,  to  state,  that  the  parting 
line  between  the  Bembridge  and  Hempstead  series,  in  the  Isle 
of  Wight,  has  been  shown  by  Prof.  Forbes  to  be  an  arbitrary  one 
—  a  purely  conventional  line,  if  anything,  less  marked  than  the 
line  separating  the  Bembridge  series  from  the  underlying  St. 
Helen's  group.  (See  Table,  p.  209.)  If  retained  as  more  useful,  it  is, 
as  before  hinted,  for  the  sake  of  conformity  with  a  system  of  classi- 
fication adopted  by  many  able  geologists,  who  selected  it  before 
the  uninterrupted  continuity  of  the  Eocene  series  from  its  nummu- 


CH.  XV.]  LIMBURG   STRATA   IN   BELGIUM.  189 

litic  or  central  portions  to  its  Upper  or  Limburg  beds  was  clearly 
made  out. 


LIMBURG   STRATA   IN  BELGIUM. 

(Rupelian  and  Tongrian  Systems  of  Dumont.) 

The  best  type  which  we  as  yet  possess  of  the  Upper  Eocene,  as  de- 
fined in  the  foregoing  observations,  consists  of  the  beds  formerly 
known  to  collectors  as  those  of  Kleyn  Spawen.  These  can  be  best 
studied  in  the  environs  of  the  village  so  named,  which  is  situated 
about  seven  miles  west  of  Maestricht,  and  in  the  old  province  of 
Limburg  in  Belgium.  In  that  region,  about  200  species  of  testacea, 
marine  and  freshwater,  have  been  obtained,  with  many  foraminifera 
and  remains  offish. 

The  following  table  will  show  the  position  of  the  Limburg  beds. 

MIOCENE. 
A.  Bolderberg  beds,  see  p.  179.,  seen  near  Hasselt. 

UPPER  EOCENE. 

B.  1.  Nucula    Loam    of   Kleyn    Spawen,  •)_.-.         _ . 

same  age  as  clay  of  Kupelmonde  1  Upper  Limburg  beds.  _  Rupehan  of 
and  Boom.  J      JJumont' 

B.  2.  Fluvio-marine  beds  of  Bergb,  Lelhen,  }  Middle  Limburg  beds. — Upper  Ton- 
and  other  places  near  Kleyn  Spawen.  j      grian  of  Dumont. 

B.  3.  Green  sand  of  Bergh,  Neerepen,  &c.,  )  Lower  Limburg  beds. — Lower  Ton- 
near  Kleyn  Spawen :  Marine.  j      grian  of  Dumont. 

MIDDLE  EOCENE. 

C.  Lacken  and  Brussels  beds,  with  num- 
mulites,  &c. :  Louvain  and  Brussels. 

The  uppermost  of  the  three  subdivisions  (B.  1.)  into  which  the  Lim- 
burg series  is  separated  in  the  above  table,  contains  at  Kleyn  Spawen 
many  of  the  same  fossils  as  the  clay  of  Rupelmonde  and  Boom,  ten  miles 
south  of  Antwerp,  and  sixty  miles  N.  W.  of  Kleyn  Spawen.  About 
forty  species  of  shells  have  been  collected  from  the  tile-clay  worked 
on  the  banks  of  the  Scheldt  at  the  villages  above  mentioned.  At 
Rupelmonde,  this  clay  attains  a  thickness  of  about  100  feet,  and 
much  resembles  in  mineral  character  the  "London  Clay,"  containing 
like  it  septaria  or  concretions  of  argillaceous  limestone  traversed  by 
cracks  in  the  interior.  The  shells  have  been  described  by  MM. 
Nyst  and  De  Koninck.  Among  them  Leda  (or  Nucula)  Deshayesiana 
(see  fig.  167.)  is  by  far  the  most  abundant ;  a  fossil  unknown  as  yet  in 

Fig.  167. 


Lcda  Deshayesfwa.    Nyst.    Syn    Nucula  Deshayesiana. 


190  STRATA    IN   NORTH   GERMANY.  [Cn.  XV. 

the  English  tertiary  strata,  but  when  young  much  resembling  Leda 
amygdaloides  of  the  London  clay  proper  (see  fig.  227.  p.  219.).  Among 
other  characteristic  shells  are  Pecten  Hoeninghausii,  and  a  species  of 
Cassidaria,  and  several  of  the  genus  Pleurotoma.  !Not  a  few  of  these 
testacea  agree  with  English  Eocene  species,  such  as  Actceon  simulates, 
Sow.,  Cancellaria  evulsa,  Brander,  Corbula  pisum  (fig.  170.  p.  194.), 
and  Nautilus  ziczac.  They  are  accompanied  by  many  teeth  of  sharks, 
as  Lamna  contortidcns,  Ag.,  Oxyrhina  xiphodon,  Ag.,  Carcharodon 
heterodon  (see  fig.  211.),  Ag.,  and  other  fish,  some  of  them  common  to 
the  Middle  Eocene  strata.  The  same  deposit,  B.  1 .,  is  very  imperfectly 
seen  at  Kleyn  Spawen,  where  the  lower  divisions  B.  2.  and  B.  3.  are 
much  better  developed.  B.  2.  consists  of  several  alternations  of  sands 
and  marls,  in  which  a  greater  or  less  intermixture  of  fluviatile  and 
marine  shells  occurs,  implying  the  occasional  entrance  of  a  river  near 
the  spot,  and  possibly  oscillations  in  the  level  of  the  bottom  of  the  sea. 
Among  the  shells  are  found  Cyrena  semistriata  (fig.  171.  p.  194.),  Ceri- 
thium  plicatum,  Lam.  (fig.  172.  p.  194.),  Rissoa  Chastelii,  Bosq.  (fig. 
174.),  and  Corbula  pisum  (fig.  170.),  four  shells  all  common  to  the 
Hempstead  beds  in  the  Isle  of  Wight,  to  be  mentioned  in  the  sequel. 
With  the  above,  Lucina  Thierensii,  and  other  marine  forms  of  the 
genera  Venus,  Limopsis,  Trochus,  &c.,  are  met  with. 

In  B.  3.,  or  the  Lower  Limburg,  more  than  100  marine  shells  have 
been  collected,  among  which  the  Ostrea  ventilabrum  is  very  con- 
spicuous. Species  common  to  the  underlying  Brussels  sands,  or 
the  Middle  Eocene,  are  numerous,  constituting  a  third  of  the  whole ; 
but  most  of  these  are  feebly  represented  in  comparison  with  the 
more  peculiar  and  characteristic  shells,  such  as  Ostrea  ventilabrum, 
Mytilus  Nystii,  Valuta  suturalis,  &c. 

In  none  of  the  Belgian  Upper  Eocene  strata  could  I  find  any 
nummulites ;  and  M.  D'Archiac  had  previously  observed  that  these 
foraminifera  characterize  his  "  Lower  Tertiary  Series,"  as  contrasted 
with  the  Middle,  and  would  therefore  serve  as  a  good  test  of  age 
between  Eocene  and  Miocene,  if  the  line  of  demarcation  be  drawn 
according  to  his  method,  or  equally  so  between  Upper  and  Middle 
Eocene,  according  to  the  plan  adopted  in  this  work.  The  same  natu- 
ralist informs  us  that  one  nummulite  only  has  ever  yet  been  seen  to 
penetrate  upwards  into  the  middle  tertiary,  viz.  Nummulites  inter- 
media, an  Eocene  species.  It  has  been  found  in  the  hill  of  the 
Superga  near  Turin*,  in  beds  usually  classed  as  Miocene,  but  pro- 
bably somewhat  older  than  the  falunian  type. 

Hermsdorf,  near  Berlin. — Professor  Beyrich  has  described  a  mass 
of  clay,  used  for  making  tiles  within  seven  miles  of  the  gates  of  Berlin, 
near  the  village  of  Hermsdorf,  rising  up  from  beneath  the  sands  with 
which  that  country  is  chiefly  overspread.  This  clay  is  more  than 
forty  feet  thick,  of  a  dark  bluish-grey  colour,  and,  like  that  of 
Rupelmonde,  contains  septaria.  Among  other  shells,  the  Leda 
Deshayesiana  before  mentioned  (fig.  167.)  abounds,  together  with 

*  Archiac.  Monogr.  pp.  79.  100. 


CH.  XV.]  MAYENCE   BASIN.  191 

many  species  of  Pleurotoma,  Voluta,  &c.,  a  certain  proportion  of  the 
fossils  being  identical  in  species  with  Limburg  and  Mayence  shells. 
M.  Beyrich  enumerates  several  other  localities  in  North  Germany, 
and  particularly  one  at  Magdeburg,  and  several  on  the  Lower  Elbe, 
where  beds  of  the  same  age  appear. 

Mayence  basin.  —  I  have  already  alluded  to  the  elaborate  descrip- 
tion published  by  Dr.  F.  Sandberger  of  the  Mayence  tertiary  area, 
which  occupies  a  tract  from  five  to  twelve  miles  in  breadth,  extend- 
ing for  a  great  distance  along  the  left  bank  of  the  Rhine  from 
Mayence  to  the  neighbourhood  of  Manheim,  and  which  is  also  found 
to  the  east,  north,  and  south-west  of  Frankfort.  M,  De  Koninck, 
of  Liege,  first  pointed  out  to  me  that  the  purely  marine  portion  of 
the  deposit  (the  Lower  group  of  Dr.  Sandberger)  contained  many 
species  of  shells  common  to  the  Limburg  beds  near  Kleyn  Spawen, 
and  to  the  clay  of  Rupelmonde,  near  Antwerp.  Among  these  he 
mentioned  Cassidaria  depressa,  Tritonium  argutum,  Brander  (  T.flan- 
dricum,  De  Koninck),  Tornatella  simulata,  Rostellaria  Sowerbyi, 
Leda  Deshayesiana  (fig.  167.  p.  189.),  Corbula  pisum  (fig.  170.),  and 
Pectunculus  terebratularis. 

The  marine  beds  are  in  some  places  covered  with  brackish-water 
marls  containing  Cyrence  in  great  numbers,  among  which  Cyrena 
semistriata  occurs,  with  Cerithium  plicatum.  Corbulomya  triangula, 
Mytilus  Fanjasii,  and  other  Limburg  and  Hempstead  shells.  Perna 
Soldani,  a  shell  of  the  upper  Eocene  or  Merignac  beds  of  the  Bor- 
deaux basin,  but  also  a  Vienna  basin  shell,  is  characteristic  both 
of  the  marine  and  brackish  series.  Two  species  of  Anthracothe- 
rium,  A.  magnum,  Cuv.,  and  A.  alsaticum,  are  met  with  in  the  same 
deposits. 

The  upper  portion  of  this  Mayence  series  has  at  its  base  a 
limestone  full  of  Cerithia  and  land-shells ;  among  which  Cerithium 
plicatum  before  mentioned,  and  another  Limburg  shell,  Venus  in- 
crassata.  Sow.,  a  fossil  common  to  the  Headon  or  Middle  Eocene  of 
England,  are  met  with  ;  also  Neritina  concava  (fig.  194.),  a  Middle 
Eocene  shell,  and  Rhinoceros  incisivus,  the  oldest  form  of  that  genus, 
and  called  by  Kaup  Acerotherium.  Next  above  is  a  limestone,  in 
which  Littorinella  or  Paludina  inflata  is  a  very  common  fossil,  with 
Fig.  168.  others  of  the  same  genus.  One  of  these,  very  nearly  re- 
sembling the  recent  Littorinella  ulva,  is  found  throughout 
this  basin.  These  shells  are  like  grains  of  rice  in  size, 
and  are  often  in  such  quantity  as  to  form  entire  beds  of 
marl  and  limestone,  in  stratified  masses  from  fifteen  to 
thirty  feet  in  thickness,  just  as  in  the  Baltic  modern  accu- 
mulations several  feet  thick  of  the  Littorinella  ulva  are  spread  far 
and  wide  over  the  bottom  of  the  sea.  In  the  same  beds,  several 
species  of  Dreissena  abound,  a  form  common  to  the  Headon  or 
Middle  Eocene  beds  of  the  Isle  of  Wight,  as  well  as  to  the  existing 
seas.  On  the  whole,  I  am  not  satisfied  that  this  fauna  diverges  from 
the  Limburg  type  towards  that  of  the  faluns  as  much  as  Dr.  Sand- 
berger believes.  Among  the  Mammalia,  we  find  Hippotherium 
gracile,  Acerotherium  (or  Rhinoceros)  incisivum,  Paleomeryx,  Cha- 


192 


BROWN   COAL    OF    GERMANY. 


[CH.  XV. 


licbmyt,8tC.  Lastly,  theEppelslieim  sand  overlies  the  whole,  containing 
Deinotherium  giganteum,  and  some  other  true  Miocene  quadrupeds. 
Several  mammalia,  proper  to  the  Upper  Eocene  series,  are  also  said 
to  be  associated ;  but  there  being  no  good  section  at  Eppelsheim, 
the  true  succession  of  the  beds  from  which  the  bones  were  dug  out 
cannot  be  seen,  and  we  have  yet  to  learn  whether  some  remains  of  an 
older  series  may  not  have  been  confounded  with  those  of  a  newer  one. 
Brown  coal  of  Germany.  —  In  a  recent  essay  on  the  Brown  Coal 
deposits  of  Germany,  Baron  Von  Buch  has  expressed  a  decided 
opinion  that  they  all  belong  to  one  epoch,  being  of  subsequent  date 
to  the  great  nummulitic  period,  and  newer  than  the  Pliocene  form- 
ations. He  has  therefore  called  the  whole  Miocene.  Unfortunately, 
these  formations  rarely  contain  any  internal  evidence  of  their  age, 
except  what  may  be  derived  from  plants,  constituting  in  every  case 
but  a  fraction  of  an  ancient  Flora,  and  consisting  of  mere  leaves, 
without  flowers  or  fruits.  It  is  often  therefore  impossible  to  form 
more  than  a  conjecture  as  to  the  precise  place  in  the  chronological 
series  which  should  be  assigned  to  each  layer  of  lignite  or  each  le;if- 
bed.  Nevertheless,  enough  is  known  to  show  that  some  of  the 
Brown  Coals  found  in  isolated  patches  belong  to  the  Upper  Eocene, 
others  to  the  Miocene,  and  some  perhaps  to  the  Pliocene  eras.  They 
seem  to  have  been  formed  at  a  period  when  the  European  area  had 
already  a  somewhat  continental  character,  so  that  few  contempora- 
neous marine  or  even  fluvio-marine  beds  were  in  progress  there. 

The  brown  coal  of  Brandenburg,  on  the  borders  of  the  Baltic, 
underlies  the  Hermsdorf  tile-clay  already  spoken  of,  and  therefore 
belongs  to  a  period  at  least  as  old  as  the  Upper  Eocene  The 
brown  coal  of  Radoboj,  on  the  confines  of  Styria,  is  covered,  says  Von 
Buch,  by  beds  containing  the  marine  shells  of  the  Vienna  basin, 

which,  as  before  remarked,  are  chiefly 
of  the  Falunian  or  Miocene  type.  This 
lignite,  therefore,  may  be  of  Miocene  or 
Upper  Eocene  date,  a  point  to  be  deter- 
mined by  the  botanical  characters  of  the 
plants.  In  this,  and  most  of  the  princi- 
pal brown  coal  formations,  several  spe- 
cies of  fan-palm  or  Flabellaria  abound. 
This  genus  also  appears  in  the  Middle 
Eocene  or  Bembridge  beds  in  the  Isle 
of  Wight,  and  in  the  gypseous  series  of 
Montmartre ;  but  it  is  still  more  largely 
represented  in  the  Upper  Eocene  series, 
accompanied  by  palms  of  the  genus  Phce- 
nicites.  Various  cones,  and  the  leaves 
and  wood  of  coniferous  trees,  are  also 
met  with  at  Radoboj.  Species  also  of 
Comptonia  and  Myrica,  with  various 

Daphnogene  cinnamomif.jlia,  AltsatteL    trees,  SUCh    as    the    plane     Or   PlatailUS, 

in  Bohemia.  are  recognized  by  their  leaves,  as  also 


Fig.  169. 


CH.  XV.]         UPPER   EOCENE    STRATA   OF   ENGLAND.  193 

several  of  the  Laurel  tribe,  especially  one,  called  Daphnogene  cinna- 
momifolia  (fig.  16y.)  by  linger,  who,  together  with  Goppert,  has 
investigated  the  botany  of  these  formations.  It  will  be  seen  that 
in  the  leaf  of  this  Daphnogene  two  veins  branch  off  on  each  side 
from  the  mid-rib,  and  run  up  without  interruption  to  the  point. 

On  the  Lower  Rhine,  whether  in  theMayence  basin  or  in  the  Sieben- 
gebirge,  and  in  the  neighbourhood  of  Bonn  and  Cologne,  there  seem 
to  be  Brown  Coals  of  more  than  one  age.  Von  Buch  tells  us  that  the 
only  fossil  found  in  the  Brown  Coal  near  Cologne,  one  often  met  with 
there  in  the  excavation  of  a  tunnel,  is  the  peculiar  fruit,  so  like  a 
cocoa-nut,  called  Nipadites  or  Burtonia  Fanjasii  (see  fig.  220.).  Now 
this  fossil  abounds  in  the  Lower  Eocene  or  Sheppy  clay  near  London, 
also  in  the  Middle  Eocene  at  Brussels ;  and  I  found  it  still  higher  in 
the  same  nummulitic  series  at  Cassel,  in  French  Flanders.  This 
fact  taken  alone  would  rather  lead  us  to  refer  the  Cologne  lignite 
to  the  Eocene  period. 

Some  of  the  lignites  of  the  Siebengebirge  near  Bonn  associated 
with  volcanic  rocks,  and  those  of  Hesse  Cassel  which  accompany 
basaltic  outpourings,  are  certainly  of  much  later  date. 

UPPER  EOCENE   STRATA   OF   ENGLAND. 

Hempstead  beds. — Isle  of  Wight. —  Until  very  lately  it  was  sup- 
posed by  English  geologists  that  the  newest  tertiary  strata  of  the 
Isle  of  Wight  corresponded  in  age  with  the  gypseous  series  of  Mont- 
martre  near  Paris  ;  and  this  idea  was  confirmed  by  the  fact  that  the 
same  species  of  Palceotherium,  Anoplotherium,  and  other  extinct  mam- 
malia so  characteristic  of  the  Parisian  series,  were  also  found  at 
Binstead,  near  Hyde,  in  the  northern  district  of  the  island,  forming 
part  of  the  fluvio-marine  series.  We  are  indebted  to  Prof.  E.  Forbes 
for  having  discovered  in  the  autumn  of  1852  that  there  exist  three 
formations,  the  true  position  of  which  had  been  overlooked,  all  of  them 
newer  than  the  beds  of  Headon  Hill,  in  Alum  Bay,  which  last  were 
formerly  believed  to  be  the  uppermost  part  of  the  Isle  of  Wight 
tertiary  series.* 

The  three  overlying  formations  to  which  I  allude  are  as  follows  :  — 
1st,  certain  shales  and  sandstones  called  the  St.  Helen's  beds  (see 
Table,  p.  105.  et  seq.)  rest  immediately  upon  the  Headon  series;  2dly, 
the  St.  Helen's  series  is  succeeded  by  the  Bembridge  beds  before 
mentioned,  the  equivalent  of  the  Montmartre  gypsum ;  and  3rdly, 
above  the  whole  is  found  the  Upper  Eocene  or  Hempstead  series. 
This  newer  deposit,  which  is  170  feet  thick,  has  been  so  called  from 
Hempstead  Hill,  near  Yarmouth,  in  the  Isle  of  Wight,  f  The  fol- 
lowing is  the  succession  of  strata  there  discovered,  the  details  of 
which  are  important  for  reasons  explained  in  the  preliminary  re- 
marks of  this  chapter  (p.  188.): — 

*  E.    Forbes,    Geol.    Quart.    Journ.      with  Hampstead  Hill,    near   London, 

1853.  where  the  Lower  Eocene  or  London 

f  This  hill  must  not  be  confounded      Clay  is  capped  by  Middle  Eocene  sands. 

o 


194 


UPPER   EOCENE,   ISLE    OF   WIGHT. 


[CH.  XV. 


SUBDIVISIONS   OF  THE   HEMPSTEAD   SERIES. 

1.  The  uppermost  or  Corbula  beds,  consisting  of  marine  sands  and  clays, 
contain  Corbula  pisum,  fig.  170.,  a  species  common  to  the  Middle  Eocene  clay 
of  Barton  ;  Cyrena  semistriata,  fig.  171.,  which  is  also  a  Middle  Eocene  fossil; 
several  Cerithia,  and  other  shells  peculiar  to  this  series. 


Fig.  170. 


Fig. 171. 


Corbula  pisum.    Hempstead  Beds, 
Isle  of  Wight. 


Cyrena  semistriata. 
Hempstead  Beds. 


2.  Next  below  are  freshwater  and  estuary  marls  and  carbonaceous  clays,  in  the 
brackish-water  portion  of  which  are  found  abundantly  Cerithium  plicatum,  Lam., 
fig.  172.,  C.  elegans,  fig.  173.,  and  C.  tricinctum;  also  Rissoa  Chastelii,  fig.  174., 
a  very  common  Limburg  shell,  and  which  occurs  in  each  of  the  four  subdivisions 
of  the  Hempstead  series  down  to  its  base,  where  it  passes  into  the  Bembridge  beds. 
In  the  freshwater  portion  of  the  same  beds  Paludina  lenta,  fig.  175.,  occurs,  a  shell 


Fig.  172. 


Fig.  173. 


Fig.  174. 


Fig.  175. 


Cerithium  plicatum, 
Lam.   Hempstead. 


Cerithium  elegant. 
Hempstead. 


Rissoa  Chastelii,  Nyst, 
Sp.  Hempstead,  isle 
of  Wight. 


Paludina  lenta. 
Hempstead  Beds. 


identified  by  some  conchologists  with  a  species  now  living,  P.  unicolor;  also 
several  species  of  Lymneus,  Planorbis,  and  Unio. 

3.  The  next  series,   or  middle  freshwater  and  estuary  marls,   are    distinguished 
by  the  presence  of  Melania  fasciata,  Paludina  lenta,  and  clays  with  Cypris;  the 
lowest  bed  contains  Cyrena  semistriata,  fig.  171.,  mingled  with  Cerithia  and  a 
Panopoea. 

4.  The   lower    freshwater    and   estuary  marls    contain   Melania    costata,   Sow., 
Melanopsis,  &c.     The  bottom  bed  is  carbonaceous,  and  called  the  "  Black  band," 
in  which  Rissoa  Chastelii,  fig.  173  ,  before  alluded  to,  is  common.     This  bed 
contains  a  mixture  of  Hempstead  shells  with  those  of  the  underlying  Middle 
Eocene  or  Bembridge  series.     The  seed-vessels  of  Chara  medicaginula,  Brong., 
and  C.  helecteras  are  characteristic   of  the  Hempstead  beds  generally.     The 
mammalia,  among  which  is  a  species  of  Hyotherium,  differ,  so  far  as  they  are 
known,  from  those  of  the  Bembridge  beds  immediately  underlying. 


CH.  XV.]    UPPER  EOCENE  STRATA  OF  FRANCE.         195 

Between  the  Hempstead  beds  above  described  and  those  next  below  thera, 
there  is  no  break,  as  before  stated,  p.  188.  The  freshwater,  brackish,  and 
marine  limestones  and  marls  of  the  underlying  or  Bembridge  group  are  in 
conformable  stratification,  and  contain  Cyrena  semistriata,  fig.  171.,  Melania 
muricata,  Paludina  lenta,  fig.  175.,  and  several  other  shells  belonging  to  the 
Hempstead  beds.  Prof.  Forbes  therefore  classes  both  of  them  in  the  same 
Upper  Eocene  division.  I  have  called  the  Bembridge  beds  Middle  Eocene, 
for  convenience  sake,  as  already  explained  (pp.  184. 188.). 

UPPER  EOCENE  STRATA  OF  FRANCE. 

(Lower  Miocene  of  many  French  authors.) 

The  Ores  de  Fontainebleau,  or  sandstone  of  the  Forest  of  Fon- 
tainebleau,  has  been  frequently  alluded  to  in  the  preceding  pages,  as 
corresponding  in  age  to  the  Limburg  or  Hempstead  beds.  It  is  as- 
sociated in  the  suburbs  of  Paris  with  a  set  of  strata,  very  varied  in 
their  composition,  and  containing  in  their  lower  portion  a  green 
clay  with  abundance  of  small  oysters  (Ostrea  cyathula,  Lam.)  which 
are  spread  over  a  wide  area.  The  marine  sands  and  sandstone 
which  overlie  this  clay  include  Cytherea  incrassata  and  many  other 
Limburg  fossils,  the  finest  collections  of  which  have  been  made  at 
Etampes,  south  of  Paris,  where  they  occur  in  loose  sand.  The  Gres 
de  Fontainebleau  is  sometimes  called  the  "  Upper  marine  sands  "  to 
distinguish  it  from  the  "Middle  sands"  or  Gres  de  Beauchamp,  a 
Middle  Eocene  group. 

Calcaire  lacustre  superieur.  —  Above  the  Gres  de  Fontainebleau 
is  seen  the  upper  freshwater  limestone  and  marl,  sometimes  called 
Calcaire  de  la  Beauce,  which  with  its  accompanying  marls  and 
siliceous  beds  seem  to  have  been  formed  in  marshes  and  shallow  lakes, 
such  as  frequently  overspread  the  newest  parts  of  great  deltas.  Beds 
of  flint,  continuous  or  in  nodules,  accumulated  in  these  lakes,  and 
Cfiarce,  aquatic  plants,  already  alluded  to,  left  their  stems  and  seed- 
vessels  imbedded  both  in  the  marl  and  flint,  together  with  freshwater 
and  land-shells.  Some  of  the  siliceous  rocks  of  this  formation 
are  used  extensively  for  millstones.  The  flat  summits  or  platforms 
of  the  hills  round  Paris — large  areas  in  the  forest  of  Fontainebleau, 
and  the  Plateau  de  la  Beauce,  between  the  Seine  and  the  Loire,  are 
chiefly  composed  of  these  upper  freshwater  strata.  When  they  reach 
the  valley  of  the  Loire,  they  occasionally  underlie  and  form  the 
boundary  of  the  marine  Miocene  faluns,  fragments  of  the  older  fresh- 
water limestone  having  been  broken  off  and  rolled  on  the  shores  and 
in  the  bed  of  the  Miocene  sea,  as  at  Pontlevoy,  on  the  Cher,  where 
the  perforating  marine  shells  of  the  Miocene  period  still  remain 
in  hollows  drilled  in  the  blocks  of  Eocene  limestone. 

Central  France.  —  Lacustrine  strata,  belonging,  for  the  most  part, 
to  the  same  Upper  Eocene  series,  are  again  met  with  in  Auvergne, 
Cantal,  and  Velay,  the  sites  of  which  may  be  seen  in  the  annexed 
map.  They  appear  to  be  the  monuments  of  ancient  lakes,  which, 
like  some  of  those  now  existing  in  Switzerland,  once  occupied  the 
depressions  in  a  mountainous  region,  and  have  been  each  fed  by  one 

o  2 


196 


UPPER  EOCENE  OF  CENTRAL  FRANCE.    [Cn.  XV. 


Fig.  176. 


or  more  rivers  and  torrents.    The  country  where  they  occur  is  almost 
entirely  composed  of  granite  and  different  varieties  of  granitic  schist, 


CH.  XV.]      SUCCESSION   OF    CHANGES   IN   AUVERGNE.  197 

with  here  and  there  a  few  patches  of  secondary  strata,  much  dislo- 
cated, and  which  have  probably  suffered  great  denudation.  There 
are  also  some  vast  piles  of  volcanic  matter  (see  the  map),  the  greater 
part  of  which  is  newer  than  the  freshwater  strata,  and  is  sometimes 
seen  to  rest  upon  them,  while  a  small  part  has  evidently  been  of 
contemporaneous  origin.  Of  these  igneous  rocks  I  shall  treat  more 
particularly  in  another  part  of  this  work. 

Before  entering  upon  any  details,  I  may  observe  that  the  study 
of  these  regions  possesses  a  peculiar  interest,  very  distinct  in  kind 
from  that  derivable  from  the  investigation  either  of  the  Parisian  or 
English  tertiary  areas.  For  we  are  presented  in  Auvergne  with  the 
evidence  of  a  series  of  events  of  astonishing  magnitude  and  grandeur, 
by  which  the  original  form  and  features  of  the  country  have  been 
greatly  changed,  yet  never  so  far  obliterated  but  that  they  may  still, 
in  part  at  least,  be  restored  in  imagination.  Great  lakes  have  dis- 
appeared,—  lofty  mountains  have  been  formed,  by  the  reiterated 
emission  of  lava,  preceded  and  followed  by  showers  of  sand  and 
scoriae,  —  deep  valleys  have  been  subsequently  furrowed  out  through 
masses  of  lacustrine  and  volcanic  origin,  —  at  a  still  later  date,  new 
cones  have  been  thrown  up  in  these  valleys,  —  new  lakes  have  been 
formed  by  the  damming  up  of  rivers, — and  more  than  one  creation  of 
quadrupeds,  birds,  and  plants,  Eocene,  Miocene,  and  Pliocene,  have 
followed  in  succession ;  yet  the  region  has  preserved  from  first  to  last 
its  geographical  identity ;  and  we  can  still  recall  to  our  thoughts  its 
external  condition  and  physical  structure  before  these  wonderful 
vicissitudes  began,  or  while  a  part  only  of  the  whole  had  been  com- 
pleted. There  was  first  a  period  when  the  spacious  lakes,  of  which 
we  still  may  trace  the  boundaries,  lay  at  the  foot  of  mountains  of 
moderate  elevation,  unbroken  by  the  bold  peaks  and  precipices  of 
Mont  Dor,  and  unadorned  by  the  picturesque  outline  of  the  Puy  de 
Dome,  or  of  the  volcanic  cones  and  craters  now  covering  the  granitic 
platform.  During  this  earlier  scene  of  repose  deltas  were  slowly 
formed ;  beds  of  marl  and  sand,  several  hundred  feet  thick,  deposited ; 
siliceous  and  calcareous  rocks  precipitated  from  the  waters  of  mineral 
springs ;  shells  and  insects  imbedded,  together  with  the  remains  of 
the  crocodile  and  tortoise ;  the  eggs  and  bones  of  water  birds,  and  the 
skeletons  of  quadrupeds,  some  of  them  belonging  to  the  same  genera 
as  those  entombed  in  the  Eocene  gypsum  of  Paris.  To  this  tranquil 
Condition  of  the  surface  succeeded  the  era  of  volcanic  eruptions,  when 
the  lakes  were  drained,  and  when  the  fertility  of  the  mountainous 
district  was  probably  enhanced  by  the  igneous  matter  ejected  from 
below,  and  poured  down  upon  the  more  sterile  granite.  During  these 
eruptions,  which  appear  to  have  taken  place  after  the  disappearance 
of  the  Upper  Eocene  fauna,  and  partly  in  the  Miocene  epoch,  the 
mastodon,  rhinoceros,  elephant,  tapir,  hippopotamus,  together  with  the 
ox,  various  kinds  of  deer,  the  bear,  hycena,  and  many  beasts  of  prey 
ranged  the  forest,  or  pastured  on  the  plain,  and  were  occasionally 
overtaken  by  a  fall  of  burning  cinders,  or  buried  in  flows  of  mud,  sucli 
as  accompany  volcanic  eruptions.  Lastly,  these  quadrupeds  became 

O  3 


198  LACUSTRINE    STRATA  —  AUVERGNE.  [Cn.  XV. 

extinct,  and  gave  place  to  Pliocene  mammalia  (see  ch.  xxxii.),  and 
these,  in  their  turn,  to  species  now  existing.  There  are  no  signs, 
during  the  whole  time  required  for  this  series  of  events,  of  the  sea 
having  intervened,  nor  of  any  denudation  which  may  not  have  been 
accomplished  by  currents  in  the  different  lakes,  or  by  rivers  and  floods 
accompanying  repeated  earthquakes,  during  which  the  levels  of  the 
district  have  in  some  places  been  materially  modified,  and  perhaps 
the  whole  upraised  relatively  to  the  surrounding  parts  of  France. 

Auvergne.  —  The  most  northern  of  the  freshwater  groups  is  situ- 
ated in  the  valley-plain  of  the  Allier,  which  lies  within  the  depart- 
ment of  the  Puy  de  Dome,  being  the  tract  which  went  formerly 
by  the  name  of  the  Limagne  d'Auvergne.  It  is  inclosed  by  two 
parallel  mountain  ranges,  —  that  of  the  Forez,  which  divides  the 
waters  of  the  Loire  and  Allier,  on  the  east ;  and  that  of  the  Monts 
Domes,  which  separates  the  Allier  from  the  Sioule,  on  the  west.* 
The  average  breadth  of  this  tract  is  about  20  miles ;  and  it  is  for 
the  most  part  composed  of  nearly  horizontal  strata  of  sand,  sand- 
stone, calcareous  marl,  clay,  and  limestone,  none  of  which  observe 
a  fixed  and  invariable  order  of  superposition.  The  ancient  borders 
of  the  lake,  wherein  the  freshwater  strata  were  accumulated,  may 
generally  be  traced  with  precision,  the  granite  and  other  ancient 
rocks  rising  up  boldly  from  the  level  country.  The  actual  junction, 
however,  of  the  lacustrine  and  granitic  beds  is  rarely  seen,  as  a  small 
valley  usually  intervenes  between  them.  The  freshwater  strata  may 
sometimes  be  seen  to  retain  their  horizontality  within  a  very  slight 
distance  of  the  border-rocks,  while  in  some  places  they  are  inclined, 
and  in  few  instances  vertical.  The  principal  divisions  into  which 
the  lacustrine  series  may  be  separated  are  the  following:  —  1st, 
Sandstone,  grit,  and  conglomerate,  including  red  marl  and  red  sand- 
stone ;  2dly,  Green  and  white  foliated  marls ;  3dly,  Limestone  or 
travertin,  often  oolitic  ;  4thly,  Gypseous  marls. 

1.  a.  Sandstone  and  conglomerate.  —  Strata  of  sand  and  gravel, 
sometimes  bound  together  into  a  solid  rock,  are  found  in  great  abun- 
dance around  the  confines  of  the  lacustrine  basin,  containing,  in 
different  places,  pebbles  of  all  the  ancient  rocks  of  the  adjoining 
elevated  country ;  namely,  granite,  gneiss,  mica-schist,  clay-slate, 
porphyry,  and  others,  but  without  any  intermixture  of  basaltic  or 
other  tertiary  volcanic  rocks.  These  strata  do  not  form  one  con- 
tinuous band  around  the  margin  of  the  basin,  being  rather  disposed 
like  the  independent  deltas  which  grow  at  the  mouths  of  torrents 
along  the  borders  of  existing  lakes. 

At  Chamalieres,  near  Clermont,  we  have  an  example  of  one  of 
these  deltas,  or  littoral  deposits,  of  local  extent,  where  the  pebbly 
beds  slope  away  from  the  granite,  as  if  they  had  formed  a  talus 
beneath  the  waters  of  the  lake  near  the  steep  shore.  A  section  of 
about  50  feet  in  vertical  height  has  been  laid  open  by  a  torrent, 
and  the  pebbles  are  seen  to  consist  throughout  of  rounded  and 

*  Scrope,  Geology  of  Central  France,  p.  15. 


CH.  XV.]  UPPER  EOCENE  PERIOD.  199 

angular  fragments  of  granite,  quartz,  primary  slate,  and  red  sand- 
stone. Partial  layers  of  lignite  and  pieces  of  wood  are  found  in  these 
beds. 

At  some  localities  on  the  margin  of  the  basin  quartzose  grits  are 
found  ;  and,  where  these  rest  on  granite,  they  are  sometimes  formed 
of  separate  crystals  of  quartz,  mica,  and  felspar,  derived  from  the 
disintegrated  granite,  the  crystals  having  been  subsequently  bound 
together  by  a  siliceous  cement.  In  these  cases  the  granite  seems 
regenerated  in  a  new  and  more  solid  form ;  and  so  gradual  a  passage 
takes  place  between  the  rock  of  crystalline  and  that  of  mechanical 
origin,  that  we  can  scarcely  distinguish  where  one  ends  and  the 
other  begins. 

In  the  hills  called  the  Puy  de  Jussat  and  La  Roche,  we  have  the 
advantage  of  seeing  a  section  continuously  exposed  for  about  700  feet 
in  thickness.  At  the  bottom  are  foliated  marls,  white  and  green, 
about  400  feet  thick ;  and  above,  resting  on  the  marls,  are  the  quartzose 
grits,  cemented  by  calcareous  matter,  which  is  sometimes  so  abundant 
as  to  form  imbedded  nodules.  These  sometimes  constitute  spheroidal 
concretions  6  feet  in  diameter,  and  pass  into  beds  of  solid  lime- 
stone, resembling  the  Italian  travertins,  or  the  deposits  of  mineral 
springs. 

1.  b.  Red  marl  and  sandstone. — But  the  most  remarkable  of  the 
arenaceous  groups  is  one  of  red  sandstone  and  red  marl,  which  are 
identical  in  all  their  mineral  characters  with  the  secondary  New  Red 
sandstone  and  marl  of  England.     In  these  secondary  rocks  the  red 
ground  is  sometimes  variegated  with  light  greenish  spots,  and  the 
same  may  be  seen  in  the  tertiary  formation  of  freshwater  origin  at 
Coudes,  on  the  Allier.     The  marls  are  sometimes  of  a  purplish-red 
colour,  as  at  Champheix,  and  are  accompanied  by  a  reddish-lime- 
stone, like  the  well-known  "  cornstone,"  which  is  associated  with  the 
Old  Red  sandstone  of  English  geologists.     The  red  sandstone  and 
marl  of  Auvergne  have  evidently  been  derived  from  the  degradation 
of  gneiss  and  mica-schist,  which  are  seen  in  situ  on  the  adjoining 
hills,  decomposing  into  a  soil  very  similar  to  the  tertiary  red  sand 
and  marl.     We  also  find  pebbles  of  gneiss,  mica-schist,  and  quartz 
in   the  coarser  sandstones  of  this  group,   clearly  pointing   to  the 
parent  rocks  from  which  the  sand  and  marl  are  derived.     The  red 
beds,  although  destitute  themselves  of  organic  remains,  pass  upwards 
into  strata  containing  tertiary  fossils,  and  are  certainly  an  integral 
part  of  the  lacustrine  formation.     From  this  example  the  student 
will  learn  how  small  is  the  value  of  mineral  character  alone,  as  a 
test  of  the  relative  age  of  rocks. 

2.  Green  and  white  foliated  marls. — The  same  primary  rocks  of 
Auvergne,  which,  by  the  partial  degradation  of  their  harder  parts, 
gave  rise  to  the  quartzose  grits  and  conglomerates  before  mentioned, 
would,  by  the  reduction  of  the  same  materials  into  powder,  and  by 
the  decomposition  of  their  felspar,  mica,  and  hornblende,  produce 
aluminous  clay,  and,  if  a  sufficient  quantity  of  carbonate  of  lime 
was  present,  calcareous  marl.     This  fine  sediment  would  naturally 

o  4 


200  LACUSTRINE   STRATA  —  AUVERGNE.  [Cn.  XV. 

be  carried  out  to  a  greater  distance  from  the  shore,  as  are  the 
various  finer  marls  now  deposited  in  Lake  Superior.  And  as,  in  the 
American  lake,  shingle  and  sand  are  annually  amassed  near  the 
northern  shores,  so  in  Auvergne  the  grits  and  conglomerates  before 
mentioned  were  evidently  formed  near  the  borders. 

The  entire  thickness  of  these  marls  is  unknown ;  but  it  certainly 
exceeds,  in  some  places,  700  feet.  They  are,  for  the  most  part, 
either  light-green  or  white,  and  usually  calcareous.  They  are 
thinly  foliated, — a  character  which  frequently  arises  from  the  in- 
numerable thin  shells,  or  carapace-valves,  of  that  small  animal  called 
Cypris.  This  animal  is  provided  with  two  small  valves,  not  unlike 
those  of  a  bivalve  shell,  and  moults  its  integuments  periodically, 
which  the  conchiferous  mollusks  do  not.  This  circumstance  may 
partly  explain  the  countless  myriads  of  the  shells  of  Cypris  which 
were  shed  in  the  ancient  lakes  of  Auvergne,  so  as  to  give  rise  to 
divisions  in  the  marl  as  thin  as  paper,  and  that,  too,  in  stratified 
masses  several  hundred  feet  thick.  A  more  convincing  proof  of  the 
tranquillity  and  clearness  of  the  waters,  and  of  the  slow  and  gradual 
process  by  which  the  lake  was  filled  up  with  fine  mud,  cannot  be 
desired.  But  we  may  easily  suppose  that,  while  this  fine  sediment 
was  thrown  down  in  the  deep  and  central  parts  of  the  basin,  gravel, 
sand,  and  rocky  fragments  were  hurried  into  the  lake,  and  deposited 
near  the  shore,  forming  the  group  described  in  the  preceding  section. 

Not  far  from  Clermont,  the  green  marls,  containing  the  Cypris  in 
abundance,  approach  to  within  a  few  yards  of  the  granite  which  forms 
the  borders  of  the  basin.  The  occurrence  of  these  marls  so  near  the 
ancient  margin  may  be  explained  by  considering  that,  at  the  bottom  of 
the  ancient  lake,  no  coarse  ingredients  were  deposited  in  spaces  inter- 
mediate between  the  points  where  rivers  and  torrents  entered,  but 

Fig.  177. 


Vertical  strata  of  marl,  at  Champradelle,  near  Clermont. 

A.  Granite.  B.  Space  of  60  feet,  in  which  no  section  is  seen. 

C.  Green  marl,  vertical  and  inclined.  D.  white  marl. 

finer  mud  only  was  drifted  there  by  currents.  The  vertically  of 
some  of  the  beds  in  the  above  section  bears  testimony  to  considerable 
local  disturbance  subsequent  to  the  deposition  of  the  marls ;  but  such 
inclined  and  vertical  strata  are  very  rare. 

3.  Limestone,  travertin,  oolite. — Both  the  preceding  members  of 
the  lacustrine  deposit,  the  marls  and  grits,  pass  occasionally  into 
limestone.  Sometimes  only  concretionary  nodules  abound  in  them  ; 
but  these,  where  there  is  an  increase  in  the  quantity  of  calcareous 
matter,  unite  into  regular  beds. 


Cn.  XV.] 


INDUSIAL    LIMESTONE. 


201 


On  each  side  of  the  basin  of  the  Limagne,  both  on  the  west  at 
Gannat,  and  on  the  east  at  Vichy,  a  white  oolitic  limestone  is  quar- 
ried. At  Vichy,  the  oolite  resembles  our  Bath  stone  in  appearance 
and  beauty;  and,  like  it,  is  soft  when  first  taken  from  the  quarry, 
but  soon  hardens  on  exposure  to  the  air.  At  Gannat,  the  stone 
contains  land-shells  and  bones  of  quadrupeds.  At  Chadrat,  in  the 
hill  of  La  Serre,  the  limestone  is  pisolitic,  the  small  spheroids  com- 
bining both  the  radiated  dnd  concentric  structure. 

Indusial  limestone.  —  There  is  another  remarkable  form  of  fresh- 
water limestone  in  Auvergne,  called  "  indusial,"  from  the  cases,  or 
indusicB,  of  caddis-worms  (the  larvse  of  Phryganea) ;  great  heaps  of 
which  have  been  incrusted,  as  they  lay,  by  carbonate  of  lime,  and 
formed  into  a  hard  travertin.  The  rock  is  sometimes  purely  cal- 
careous, but  there  is  occasionally  an  intermixture  of  siliceous  matter. 
Several  beds  of  it  are  frequently  seen,  either  in  continuous  masses, 
or  in  concretionary  nodules,  one  upon  another,  with  layers  of  marl 
interposed.  The  annexed  drawing  (fig.  178.)  will  show  the  manner 
in  which  one  of  these  indusial  beds  (a)  is  laid  open  at  the  surface, 
between  the  marls  (b  b),  near  the  base  of  the  hill  of  Gergovia ;  and 
affords,  at  the  same  time,  an  example  of  the'  extent  to  which  the 
lacustrine  strata,  which  must  once  have  filled  a  hollow,  have  been 
denuded,  and  shaped  out  into  hills  and  valleys,  on  the  site  of  the 
ancient  lakes. 

Fig.  178. 


Bed  of  indusial  limestone,  interstratified  with  freshwater  marl,  near  Clermont  (Kleinschrod;. 

We  may  often  observe  in  our  ponds  the  Phryganea  (or  Caddis- 
fly),  in  its  caterpillar  state,  covered  with  small  freshwater  shells,  which 
they  have  the  power  of  fixing  to  the  outside  of  their  tubular  cases, 
in  order,  probably,  to  give  them  weight  and  strength.  The  individual 


202  UPPER   EOCENE    PERIOD.  [Cn.  XV. 

figured  in  the  annexed  cut,  which  belongs  to  a  species  very  abundant 
Fig.  179.  in  England,  has  covered  its  case  with 
shells  of  a  small  Planorbis.  In  the  same 
manner  a  large  species  of  caddis-worm 
which  swarmed  in  the  Eocene  lakes  of 
Auvergne  was  accustomed  to  attach  to 
its  dwelling  the  shells  of  a  small  spiral 

Larva  of  recent  Phryganea.*  univalve  Of  the  genUS  Pdludina.  A  hun- 
dred of  these  minute  shells  are  sometimes  seen  arranged  around  one 
tube,  part  of  the  central  cavity  of  which  is  often  empty,  the  rest 
being  filled  up  with  thin  concentric  layers  of  travertin.  The  cases 
have  been  thrown  together  confusedly,  and  often  lie,  as  in  fig.  180., 

Fig.  180. 


o.  Indusial  limestone  of  Auvergne.  b.  Fossil  Paludtna  magnified. 

at  right  angles  one  to  the  other.  When  we  consider  that  ten  or 
twelve  tubes  are  packed  within  the  compass  of  a  cubic  inch,  and 
that  some  single  strata  of  this  limestone  are  6  feet  thick,  and  may  be 
traced  over  a  considerable  area,  we  may  form  some  idea  of  the  count- 
less number  of  insects  and  mollusca  which  contributed  their  integu- 
ments and  shells  to  compose  this  singularly  constructed  rock.  It  is 
unnecessary  to  suppose  that  the  Phryganece  lived  on  the  spots  where 
their  cases  are  now  found ;  they  may  have  multiplied  in  the  shallows 
near  the  margin  of  the  lake,  or  in  the  streams  by  which  it  was  fed, 
and  their  cases  may  have  been  drifted  by  a  current  far  into  the  deep 
water. 

In  the  summer  of  1837,  when  examining,  in  company  with  Dr. 
Beck,  a  small  lake  near  Copenhagen,  I  had  an  opportunity  of  wit- 
nessing a  beautiful  exemplification  of  the  manner  in  which  the 
tubular  cases  of  Auvergne  were  probably  accumulated.  This  lake, 
called  the  Fuure-Soe,  occurring  in  the  interior  of  Seeland,  is  about 
twenty  English  miles  in  circumference,  and  in  some  parts  200  feet  in 
depth.  Round  the  shallow  borders  an  abundant  crop  of  reeds  and 
rushes  may  be  observed,  covered  with  the  indusise  of  the  Phryganea 
grandis  and  other  species,  to  which  shells  are  attached.  The  plants 
which  support  them  are  the  bulrush,  Scirpus  lacustris,  and  common 
reed,  Arundo  phragmites,  but  chiefly  the  former.  In  summer,  espe- 
cially in  the  month  of  June,  a  violent  gust  of  wind  sometimes  causes  a 
current  by  which  these  plants  are  torn  up  by  the  roots,  washed  away, 
and  floated  off  in  long  bands,  more  than  a  mile  in  length,  into  deep 
water.  The  Cypris  swarms  in  the  same  lake ;  and  calcareous  springs 

*  I  believe  that  the  British  specimen  here  figured  is  P.  rhombica,  Linn. 


CH.  XV.]  LACUSTRINE    STRATA  —  AUVERGNE.  203 

alone  are  wanting  to  form  extensive  beds  of  indusial  limestone,  like 
those  of  Auvergne. 

4.  Gypseous  marls.  —  More  than  50  feet  of  thinly  laminated 
gypseous  marls,  exactly  resembling  those  in  the  hill  of  Montmartre, 
at  Paris,  are  worked  for  gypsum  at  St.  Romain,  on  the  right  bank  of 
the  Allier.  They  rest  on  a  series  of  green  cypricliferous  marls  which 
alternate  with  grit,  the  united  thickness  of  this  inferior  group  being 
seen,  in  a  vertical  section  on  the  banks  of  the  river,  to  exceed  250  feet. 

General  arrangement,  origin,  and  age  of  the  freshwater  formations 
of  Auvergne.  —  The  relations  of  the  different  groups  above  described 
cannot  be  learnt  by  the  study  of  any  one  section  ;  and  the  geologist 
who  sets  out  with  the  expectation  of  finding  a  fixed  order  of  succes- 
sion may  perhaps  complain  that  the  different  parts  of  the  basin  give 
contradictory  results.  The  arenaceous  division,  the  marls,  and  the 
limestone  may  all  be  seen  in  some  places  to  alternate  with  each  other; 
yet  it  can  by  no  means  be  affirmed  that  there  is  no  order  of  arrange- 
ment. The  sands,  sandstone,  and  conglomerate  constitute  in  general 
a  littoral  group ;  the  foliated  white  and  green  marls,  a  contem- 
poraneous central  deposit ;  and  the  limestone  is  for  the  most  part 
subordinate  to  the  newer  portions  of  both.  The  uppermost  marls 
and  sands  are  more  calcareous  than  the  lower ;  and  we  never  meet 
with  calcareous  rocks  covered  by  a  considerable  thickness  of  quartzose 
sand  or  green  marl.  From  the  resemblance  of  the  limestones  to  the 
Italian  travertins,  we  may  conclude  that  they  were  derived  from  the 
waters  of  mineral  springs,  —  such  springs  as  even  now  exist  in  Au- 
vergne, and  which  may  be  seen  rising  up  through  the  granite,  and 
precipitating  travertin.  They  are  sometimes  thermal,  but  this  cha- 
racter is  by  no  means  constant. 

It  seems  that,  when  the  ancient  lake  of  the  Limagne  first  began  to 
be  filled  with  sediment,  no  volcanic  action  had  yet  produced  lava  and 
scoriae  on  any  part  of  the  surface  of  Auvergne.  No  pebbles,  there- 
fore, of  lava  were  transported  into  the  lake, — no  fragments  of  volcanic 
rocks  embedded  in  the  conglomerate.  But  at  a  later  period,  when  a 
considerable  thickness  of  sandstone  and  marl  had  accumulated,  erup- 
tions broke  out,'  and  lava  and  tuff  were  deposited,  at  some  spots,  al- 
ternately with  the  lacustrine  strata.  It  is  not  improbable  that  cold 
and  thermal  springs,  holding  different  mineral  ingredients  in  solution, 
became  more  numerous  during  the  successive  convulsions  attending 
this  development  of  volcanic  agency,  and  thus  deposits  of  carbonate 
and  sulphate  of  lime,  silex,  and  other  minerals  were  produced.  Hence 
these  minerals  predominate  in  the  uppermost  strata.  The  subterranean 
movements  may  then  have  continued  until  they  altered  the  relative 
levels  of  the  country,  and  caused  the  waters  of  the  lakes  to  be  drained 
off,  and  the  farther  accumulation  of  regular  freshwater  strata  to  cease. 

We  may  easily  conceive  a  similar  series  of  events  to  give  rise  to 
analogous  results  in  any  modern  basin,  such  as  that  of  Lake  Superior, 
for  example,  where  numerous  rivers  and  torrents  are  carrying  down 
the  detritus  of  a  chain  of  mountains  into  the  lake.  The  transported 
materials  must  be  arranged  according  to  their  size  and  weight,  the 


204  UPPER  EOCENE  STRATA.          [Cn.  XV. 

coarser  near  the  shore,  the  finer  at  a  greater  distance  from  land ;  but 
in  the  gravelly  and  sandy  beds  of  Lake  Superior  no  pebbles  of  modern 
volcanic  rocks  can  be  included,  since  there  are  none  of  these  at  present 
in  the  district.  If  igneous  action  should  break  out  in  that  country, 
and  produce  lava,  scoriae,  and  thermal  springs,  the  deposition  of  gravel, 
sand,  and  marl  might  still  continue  as  before ;  but,  in  addition,  there 
would  then  be  an  intermixture  of  volcanic  gravel  and  tuff,  and  of 
rocks  precipitated  from  the  waters  of  mineral  springs. 

Although  the  freshwater  strata  of  the  Limagne  approach  generally 
to  a  horizontal  position,  the  proofs  of  local  disturbance  are  sufficiently 
numerous  and  violent  to  allow  us  to  suppose  great  changes  of  level 
since  the  lacustrine  period.  We  are  unable  to  assign  a  northern 
barrier  to  the  ancient  lake,  although  we  can  still  trace  its  limits  to 
the  east,  west,  and  south,  where  they  were  formed  of  bold  granite 
eminences.  Nor  need  we  be  surprised  at  our  inability  to  restore 
entirely  the  physical  geography  of  the  country  after  so  great  a  series 
of  volcanic  eruptions ;  for  it  is  by  no  means  improbable  that  one  part 
of  it,  the  southern,  for  example,  may  have  been  moved  upwards  bodily, 
while  others  remained  at  rest,  or  even  suffered  a  movement  of  de- 
pression. 

Whether  all  the  freshwater  formations  of  the  Limagne  d'Auvergne 
belong  to  one  period,  I  cannot  pretend  to  decide,  as  large  masses  both 
of  the  arenaceous  and  marly  groups  are  often  devoid  of  fossils. 
Some  of  the  oldest  or  lowest  sands  and  marls  may  very  probably  be 
of  Middle  Eocene  date.  Much  light  has  been  thrown  on  the  mam- 
miferous  fauna  by  the  labours  of  MM.  Bravard  and  Croizet,  and  by 
those  of  M.  Pomel.  The  last-mentioned  naturalist  has  pointed  out 
the  specific  distinction  of  all,  or  nearly  all,  the  species  of  mammalia 
from  those  of  the  gypseous  series  near  Paris,  although  many  of  the 
forms  are  analogous  to  those  of  Eocene  quadrupeds.  The  Cainotlie- 
rium,  for  example,  is  not  far  removed  from  the  Anoplotherium,  and 
is,  according  to  Waterhouse.  the  same  as  the  genus  Microtherium  of 
the  Germans.  There  are  two  species  of  marsupial  animals  allied  to 
Didelphys,  a  genus  also  found  in  the  Paris  gypsum,  and  several 
forms  of  ruminants  of  extinct  genera,  such  as  Amphitragulus  ele- 
gans  of  Pomel,  which  has  been  identified  with  a  Rhenish  species 
from  Weissenau  near  Mayence,  called  by  Kaup  Dorcatherium 
nanum;  other  associated  fossils,  e.  g.,  Microtherium  Reuggeri,  and 
a  small  rodent,  Titanomys,  are  also  specifically  the  same  with  mam- 
malia of  the  Mayence  basin.  The  Hycenodon,  a  remarkable  car- 
nivorous genus,  is  represented  by  more  than  one  species,  and  the 
oldest  representative  of  the  genus  Machairodus  has  been  discovered 
in  these  beds  in  Auvergne.  The  first  of  these,  HycBnodon,  also  occurs 
in  the  English  Middle-Eocene  marls  of  Hordwell  cliff,  Hamp- 
shire, considerably  below  the  level  of  the  Bembridge  limestone,  with 
Paleotheria.  Upon  the  whole  it  is  clear  that  a  large  portion  of  the 
Limagne  rocks  have  been  correctly  referred  by  French  geologists 
to  their  Middle  Tertiary,  and  to  that  part  of  it  which  is  called 
Upper  Eocene  in  this  work. 


CH.  XV.]  UPPER   EOCENE   STRATA  —  CANTAL.  205 

Cantal. —  A  freshwater  formation,  of  about  the  same  age  and 
very  analogous  to  that  of  Aurergne,  is  situated  in  the  department  of 
Haute  Loire,  near  the  town  of  Le  Puy,  in  Velay  ;  and  another  occurs 
near  Aurillac,  in  Cantal.  The  leading  feature  of  the  formation  last 
mentioned,  as  distinguished  from  those  of  Auvergne  and  Velay,  is  the 
immense  abundance  of  silex  associated  with  calcareous  marls  and 
limestone. 

The  whole  series  may  be  separated  into  two  divisions  ;  the  lower, 
composed  of  gravel,  sand,  and  clay,  such  as  might  have  been  derived 
from  the  wearing  down  and  decomposition  of  the  granitic  schists  of 
the  surrounding  country ;  the  upper  system,  consisting  of  siliceous 
and  calcareous  marls,  contains  subordinately  gypsum,  silex,  and  lime- 
stone. 

The  resemblance  of  the  freshwater  limestone  of  the  Cantal,  and  its 
accompanying  flint,  to  the  upper  chalk  of  England,  is  very  instructive, 
and  well  calculated  to  put  the  student  upon  his  guard  against  rely- 
ing too  implicitly  on  mineral  character  alone  as  a  safe  criterion  of 
relative  age. 

When  we  approach  Aurillac  from  the  west,  we  pass  over  great 
heathy  plains,  where  the  sterile  mica-schist  is  barely  covered  with 
vegetation.  Near  Ytrac,  and  between  La-Capelle  and  Viscamp,  the 
surface  is  strewed  over  with  loose  broken  flints,  some  of  them  black 
in  the  interior,  but  with  a  white  external  coating ;  others  stained 
with  tints  of  yellow  and  red,  and  in  appearance  precisely  like  the  flint 
gravel  of  our  chalk  districts.  When  heaps  of  this  gravel  have  thus 
announced  our  approach  to  a  new  formation,  we  arrive  at  length  at 
the  escarpment  of  the  lacustrine  beds.  At  the  bottom  of  the  hill 
which  rises  before  us,  we  see  strata  of  clay  ancl  sand,  resting  on  mica- 
schist  ;  and  above,  in  the  quarries  of  Belbet,  Leybros,  and  Bruel,  a 
white  limestone,  in  horizontal  strata,  the  surface  of  which  has  been 
hollowed  out  into  irregular  furrows,  since  filled  up  with  broken  flint, 
marl,  and  dark  vegetable  mound.  In  these  cavities  we  recognize  an 
exact  counterpart  to  those  which  are  so  numerous  on  the  furrowed 
surface  of  our  own  white  chalk.  Advancing  from  these  quarries 
along  a  road  made  of  the  white  limestone,  which  reflects  as  glaring  a 
light  in  the  sun  as  do  our  roads  composed  of  chalk,  we  reach,  at 
length,  in  the  neighbourhood  of  Aurillac,  hills  of  limestone  and  cal- 
careous marl,  in  horizontal  strata,  separated  in  some  places  by  regular 
layers  of  flint  in  nodules,  the  coating  of  each  nodule  being  of  an 
opaque  white  colour,  like  the  exterior  of  the  flinty  nodules  of  our 
chalk. 

The  abundant  supply  both  of  siliceous,  calcareous,  and  gypseous 
matter,  which  the  ancient  lakes  of  France  received,  may  have  been 
connected  with  the  subterranean  volcanic  agency  of  which  those 
regions  were  so  long  the  theatre,  and  which  may  have  impregnated 
the  springs  with  mineral  matter,  even  before  the  great  outbreak  of 
lava.  It  is  well  known  that  the  hot  springs  of  Iceland,  and  many 
other  countries,  contain  silex  in  solution ;  and  it  has  been  lately 
affirmed,  that  steam  at  a  high  temperature  is  capable  of  dissolving 


206  SLOWNESS   OF    DEPOSITION.  [Cn.  XV. 

quartzose  rocks  without  the  aid  of  any  alkaline  or  other  flux.* 
Warm  water  charged  with  siliceous  matter  would  immediately  part 
with  a  portion  of  its  silex,  if  its  temperature  was  lowered  by 
mixing  with  the  cooler  waters  of  a  lake. 

A  hasty  observation  of  the  white  limestone  and  flint  of  Aurillac 
might  convey  the  idea  that  the  rock  was  of  the  same  age  as  the  white 
chalk  of  Europe  ;  but  when  we  turn  from  the  mineral  aspect  and  com- 
position to  the  organic  remains,  we  find  in  the  flints  of  the  Cantal 
seed-vessels  of  the  freshwater  Chara,  instead  of  the  marine 
zoophytes  so  abundant  in  chalk  flints ;  and  in  the  limestone  we  meet 
with  shells  of  Limnea,  Planorbis,  and  other  lacustrine  genera. 

Proofs  of  gradual  deposition.  —  Some  sections  of  the  foliated  marls 
in  the  valley  of  the  Cer,  near  Aurillac,  attest,  in  the  most  unequivocal 
manner,  the  extreme  slowness  with  which  the  materials  of  the  lacus- 
trine series  were  amassed.  In  the  hill  of  Barrat,  for  example,  we 
find  an  assemblage  of  calcareous  and  siliceous  marls ;  in  which,  for  a 
depth  of  at  least  60  feet,  the  layers  are  so  thin,  that  thirty  are 
sometimes  contained  in  the  thickness  of  an  inch ;  and  when  they  are 
separated,  we  see  preserved  in  every  one  of  them  the  flattened  stems 
of  Chares,  or  other  plants,  or  sometimes  myriads  of  small  Paludince, 
and  other  freshwater  shells.  These  minute  foliations  of  the  marl  re- 
semble precisely  some  of  the  recent  laminated  beds  of  the  Scotch 
marl  lakes,  and  may  be  compared  to  the  pages  of  a  book,  each  con- 
taining a  history  of  a  certain  period  of  the  past.  The  different  layers 
may  be  grouped  together  in  beds  from  a  foot  to  a  foot  and  a  half  in 
thickness,  which  are  distinguished  by  differences  of  composition  and 
colour,  the  tints  being  white,  green,  and  brown.  Occasionally  there 
is  a  parting  layer  of  pure  flint,  or  of  black  carbonaceous  vegetable 
matter,  about  an  inch  thick,  or  of  white  pulverulent  marl.  We  find 
several  hills  in  the  neighbourhood  of  Aurilla6  composed  of  such 
materials,  for  the  height  of  more  than  200  feet  from  their  base,  the 
whole  sometimes  covered  by  rocky  currents  of  trachytic  or  basaltic 
lava.f 

Thus  wonderfully  minute  are  the  separate  parts  of  which  some  of 
the  most  massive  geological  monuments  are  made  up!  When  we 
desire  to  classify,  it  is  necessary  to  contemplate  entire  groups  of 
strata  in  the  aggregate ;  but  if  we  wish  to  understand  the  mode  of 
their  formation,  and  to  explain  their  origin,  we  must  think  only  of 
the  minute  subdivisions  of  which  each  mass  is  composed.  We  must 
bear  in  mind  how  many  thin  leaf-like  seams  of  matter,  each  contain- 
ing the  remains  of  myriads  of  testacea  and  plants,  frequently  enter 
into  the  composition  of  a  single  stratum,  and  how  vast  a  succession  of 
these  strata  unite  to  form  a  single  group !  We  must  remember,  also, 
that  piles  of  volcanic  matter,  like  the  Plomb  du  Cantal,  which  rises 
in  the  immediate  neighbourhood  of  Aurillac,  are  themselves  equally 

*  See  Proceedings  of  Eoyal  Soc. ,  No.  Lacustres  Tertiaires  du  Cantal,  &c.  Ann. 
44.  p.  233.  des  Sci.  Nat.  Oct.  1829. 

f  Lyell  and  Murchison,  sur  les  Depots 


CH.  XV.]    UPPER  EOCENE  OF  NEBRASKA,  UNITED  STATES.     207 

the  result  of  successive  accumulation,  consisting  of  reiterated  sheets 
of  lava,  showers  of  scoriae,  and  ejected  fragments  of  rock. — Lastly, 
we  must  not  forget  that  continents  and  mountain-chains,  colossal  as 
are  their  dimensions,  are  nothing  more  than  an  assemblage  of  many 
such  igneous  and  aqueous  groups,  formed  in  succession  during  an 
indefinite  lapse  of  ages,  and  superimposed  upon  each  other. 

Bordeaux,  Aix,  &c.  —  The  Upper  Eocene  strata  in  the  Bordeaux 
basin  are  represented,  according  to  M.  Raulin,  by  the  Falun  de 
Leognan,  and  the  underlying  limestone  of  St.  Macaire.  By  many, 
however,  the  upper  of  these,  or  the  Leognan  beds,  are  considered  to 
be  no  older  than  the  faluns  of  Touraine.  The  freshwater  strata  of 
Aix-en-Provence  are  probably  Upper  Eocene ;  also  the  tertiary  rocks 
of  Malta,  Crete,  Cerigo,  and  those  of  many  parts  of  Greece  and 
other  countries  bordering  the  Mediterranean. 

Nebraska,  United  States. — In  the  territory  of  Nebraska,  on  the 
Upper  Missouri,  near  the  Platte  River,  lat.  42°  N.,  a  tertiary 
formation  occurs,  consisting  of  white  limestone,  marls,  and  siliceous 
clay,  described  by  Dr.  D.  Dale  Owen  *,  in  which  many  bones  of 
extinct  quadrupeds,  and  of  chelonians  of  land  or  freshwater  forms, 
are  met  with.  Among  these,  Dr.  Leidy  recognizes  a  gigantic 
Palceotherium,  larger  than  any  of  the  Parisian  species ;  several  species 
of  the  genus  Orcodon,  Leidy,  uniting  the  characters  of  pachyderms 
and  ruminants ;  JEucrotaphus,  another  new  genus  of  the  same  mixed 
character ;  two  species  of  rhinoceros  of  the  sub-genus  Acerotherium, 
an  Upper  Eocene  form  of  Europe  before  mentioned ;  two  of  Archtzo- 
therium,  a  pachyderm  allied  to  Chceropotamus  and  Hyracotherium ; 
also  Poebrotherium,  an  extinct  ruminant  allied  to  Dorcatherium, 
Kaup ;  also  Agriochagus  of  Leidy,  a  ruminant  allied  to  Mery- 
copotamus  of  Falconer  and  Cautley ;  and,  lastly,  a  large  carni- 
vorous animal  of  the  genus  Macairodus,  the  most  ancient  example  of 
which  in  Europe  occurs  in  the  Upper  Eocene  beds  of  Auvergne. 
The  turtles  are  referred  to  the  genus  Testudo,  but  have  some  affinity 
to  Emys.  On  the  whole,  this  formation  has,  I  believe,  been  correctly 
referred  by  American  writers  to  the  Eocene  period,  in  conformity 
with  the  classification  adopted  by  me,  but  would,  I  conceive,  be 
called  Lower  Miocene  by  those  who  apply  that  term  to  all  strata 
newer  than  the  Paris  gypsum. 

*  David  Dale  Owen,  Geol.  Survey  of  Wisconsin,  &c.:  Philad.  1852. 


208 


MIDDLE   EOCENE   FORMATIONS. 


[Cn.  XVI. 


CHAPTER  XVI. 

MIDDLE   AND   LOWER  EOCENE   FORMATIONS. 

Middle  Eocene  strata  of  England — Fluvio-marine  series  in  the  Isle  of  Wight  and 
Hampshire — Successive  groups  of  Eocene  Mammalia — Fossils  of  Barton  Clay — 
Shells,  nummulites,  fishes,  and  reptiles  of  the  Bagshot  and  Bracklesham  beds  — 
Lower  Eocene  strata  of  England  —  Fossil  plants  and  shells  of  the  London  Clay 
proper — Strata  of  Kyson  in  Suffolk — Fossil  monkey  and  opossum — Plastic 
clays  and  sands — Thanet  sands — Middle  Eocene  formations  of  France — 
Gypseous  series  of  Montmartre  and  extinct  quadrupeds — Calcaire  grossier  — 
Miliolites — Lower  Eocene  in  France — Nummulitic  formations  of  Europe  and 
Asia — Their  wide  extent — referable  to  the  Middle  Eocene  period — Eocene 
strata  in  the  United  States — Section  at  Claiborne,  Alabama  —  Colossal  cetacean 
—  Orbitoid  limestone — Burr  stone. 

THE  strata  next  in  order  in  the  descending  series  are  those  which  I 
term  Middle  Eocene.  In  the  accompanying  map,  the  position  of 
several  Eocene  areas  is  pointed  out,  such  as  the  basin  of  the  Thames, 

Fig.  181. 
Map  of  the  principal  tertiary  basins  of  the  Eocene  period. 


Hypogcne  rorks  and  strata 
older  than  the  Devonian 
or  Old  Red  series. 


Eocene  formations 


N.B.  The  space  left  blank  is  occupied  by  secondary  formations  from  the  Devonian  or  old  red 
sandstone  to  the  chalk  inclusive. 

part  of  Hampshire,  part  of  the  Netherlands,  and  the  country  round 
Paris.  The  three  last-mentioned  areas  contain  some  marine  and 
freshwater  formations,  which  have  been  already  spoken  of  as  Upper 
Eocene,  but  their  superficial  extent  in  this  part  of  Europe  is  in- 
significant. 

ENGLISH   MIDDLE   EOCENE   FORMATIONS. 

The  following  table  will  show  the  order  of  succession  of  the  strata 
found  in  the  Tertiary  areas,  commonly  called  the  London  and  Hamp- 
shire basins.  (See  also  Table,  p.  105.  et  seq.) 


CH.  XVI. ]   ENGLISH  MIDDLE  EOCENE  FORMATIONS. 

UPPER  EOCENE. 

A.      Hempstead  beds,  Isle  of  Wight,  see  above,  p.  193.  - 


209 


Thickness. 
-      170  feet. 


MIDDLE    EOCENE. 

B.  1.  Bembridge  Series,—  North  coast  of  Isle  of  Wight  -            -  120 

B.  2.  Osborne  or  St.  Helen's  Series,  —ibid.                                    -  100 

B.  3.  Headon  Series,  —  Isle  of  Wight,  and  Hordwell  Cliff,  Hants  -  170 
B.  4.  Headon  Hill  sands  and  Barton  Clay,  —  Isle  of  Wight,  and 

Barton  Cliff,  Hants                                                                -  300 
B.  5.  Bagshot    and  Bracklesham   Sands    and   Clays,  —  London 


and  Hants  basins  - 


-     700 


LOWER  EOCENE. 

C.  1.  London  Clay  proper  and  Bognorbeds,  —  London  and  Hants 

basins  -  -  350  to  500 

C.  2.  Plastic  and  Mottled  Clays  and  Sands  (Woolwich  and 

Reading  series),  —  London  and  Hants  basins  -  -  100 

C.  3.  Thanet  Sands,  —  Keculvers,  Kent,  and  Eastern  part  of 

London  basin  -  -  90 

The  true  place  of  the  Bagshot  sands,  B.  5.  in  the  above  series,  and 
of  the  Thanet  sands,  C.  3.,  was  first  accurately  ascertained  by  Mr. 
Prestwich  in  1847  and  1852.  The  true  relative  position  of  the 
Hempstead  beds,  A.,  of  the  Bembridge,  B.  I.,  and  of  the  Osborne  or 
St.  Helen's  series,  B.  2.,  were  not  made  out  in  a  satisfactory  manner 
till  Professor  Forbes  studied  them  in  detail  in  1852. 

Bembridge  series,  B.  1.  —  These  beds  are  above  100  feet  thick, 
and,  as  before  stated  (p.  188.),  pass  upwards  into  the  Hempstead  beds, 
with  which  they  are  conformable,  near  Yarmouth,  in  the  Isle  of  Wight. 
They  consist  of  marls,  clays,  and  limestones  of  freshwater,  brackish, 
and  marine  origin.  Some  of  the  most  abundant  shells,  as  Cyrena 
semistriata  var.,  and1  Paludina  lenta,  fig.  175.  p.  194.,  are  common  to 
this  and  to  the  overlying  Hempstead  series.  The  following  are  the 
subdivisions  described  by  Professor  Forbes  :  — 

a.  Upper  marls,  distinguished  by  the  abundance  of  Melania  turritissima,  Forbes 
(fig.  182.). 

Fig.  182.  Fig.  183. 


Melania  turritissima,  Forbes. 
Bembridge. 


Fragment  of  Carapace  of  Trionyx, 
Bembridge  Beds,  Isle  of  Wight. 


6.  Lower  marl,   characterized  by  Cerithium  mutabile,   Cyrena  pulchra,  &c.,  and 
by  the  remains  of  Trionyx  (see  fig.  183.). 

c.  Green  marls,  often  abounding  in  a  peculiar  species  of  oyster,  and  accompanied 

by  Cerithia,  Mytili,  an  Area,  a  Nucula,  &c. 

d.  Bembridge  limestones,  compact  cream-coloured  limestones   alternating  with 


210        FLUVIO-MAEINE  SERIES  IN  ISLE  OP  WIGHT.        [Cn.  XVI. 

shales  and  marls,  in  all  of  which  land-shells  are  common,  especially  at  Sconce, 
near  Yarmouth,  and  have  been  described  by  Mr.  Edwards.  The  Bulimus  el- 
lipticus,  fig.  184.,  and  Helix  occlusa,  fig.  185.,  are  among  its  best  known  land- 


Fig.  184. 


Fig.  185. 


Fig.  186. 


Bulimus  ellipticus,  Sow. 
Bembridge  Limestone, 
half  natural  size. 


Helix  occlusa,  Edwards, 
Sconce  Limestone, 
Isle  of  Wight. 


Paludina  orbicularts.     Bembridge. 


shells.     Paludina  orbicularis,  fig.  186.,  is  also  of  frequent  occurrence.     One  of  the 
bands  is  filled  with  a  little  globular  Paludina.    Among  the  freshwater  pulmo- 


Fig.  187. 


Fig.  188. 


Fig.  189. 


Planorbis  discus,  Edwards.    Bem- 
bridge.   |  diam. 


Lymnca  longiscata,  Brard. 


Char  a  tubercnlata. 
Bembridge  Lime- 
stone, I.  of  Wight. 


nifera,  Lymnea  longiscata  (fig.  188.)  and  Planorbis  discus  (fig.  187.)  are  the 
most  generally  distributed  :  the  latter  represents  or  takes  the  place  of  the 
Planorbis  euomphalus  (see  fig.  192.),  of  the  more  ancient  Headon  series.  Chara 
tuberculata  (fig.  189.)  is  the  characteristic  Bembridge  gyrogonite. 

From  this  formation  on  the  shores  of  Whitecliff  Bay,  Dr.  Mantell 
obtained  a  fine  specimen  of  a  fan  palm,  Fldbellaria  Lamanonis, 
Brong.,  a  plant  first  obtained  from  beds  of  corresponding  age  in  the 
suburbs  of  Paris.  The  well-known  building -stone  of  Binstead,  near 
Ryde,  a  limestone  with  numerous  hollows  caused  by  Cyrence  which 
have  disappeared  and  left  the  moulds  of  their  shells,  belongs  to  this 
subdivision  of  the  Bembridge  series.  In  the  same  Binstead  stone  Mr. 
Pratt  and  the  Rev.  Darwin  Fox  first  discovered  the  remains  of  mam 
malia  characteristic  of  the  gypseous  series  of  Paris,  as  Pal&otherium 


Fig.  190. 


CH.  XVI.]        TLUVIO-MAKINE  SERIES  IN  ISLE  OF  WIGHT.        211 

magnum, (fig.  191.)  P.  medium,  P.minus,  P.  mimi- 
mum,  P.  curium,  P.  crassum;  also  Anoplotherium 
commune  (fig.  190.),  A.  secundarium,  Dichobune 
cervinum,  and  Ch&ropotamus  Cuvieri.  The  genus 
Paleothere,  above  alluded  to,  resembled  the  living 
tapir  in  the  form  of  the  head,  and  in  having  a 
short  proboscis,  but  its  molar  teeth  were  more  like 
those  of  the  rhinoceros  (see  fig.  190.).  Paleothe- 
rium  magnum  was  of  the  size  of  a  horse,  three  or 
four  feet  high.  The  annexed  woodcut,  fig.  191., 
of  the  restorations  which  Cuvier  attempted  of  the  outline  of 


Lower  Molar  tooth, 

nat.  size, 

Anoplotherium  commune. 
Binatead,  Isle  of  Wight. 


is  one 


Fig.  191. 


Paleotherium  magnum,  Cuvier. 

the  living  animal,  derived  from  the  study  of  the  entire  skeleton.  As 
the  vertical  range  of  particular  species  of  quadrupeds,  so  far  as  our 
knowledge  extends,  is  far  more  limited  than  that  of  the  testacea ; 
the  occurrence  of  so  many  species  at  Binstead,  agreeing  with  fossils 
of  the  Paris  gypsum,  strengthens  the  evidence  derived  from  shells 
and  plants  of  the  synchronism  of  the  two  formations. 

Osborne  or  St.  Helen's  series,  B.  2.  —  This  group  is  of  fresh  and 
brackish-water  origin,  and  very  variable  in  mineral  character  and 
thickness.  Near  Hyde,  it  supplies  a  freestone  much  used  for  building, 
and  called  by  Prof.  Forbes  the  Nettlestone  grit.  In  one  part  ripple- 
marked  flag-stones  occur,  and  rocks  with  fucoidal  markings.  The 
Osborne  beds  are  distinguished  by  peculiar  species  of  Paludina,  Me- 
lania,  and  Melanopsis,  as  also  of  Cypris  and  the  seeds  of  Chara. 

Headon  series,  B.  3.  —  These  beds  are  seen  both  at  the  east 
and  west  extremities  of  the  Isle  of  Wight,  and  also  in  Hordwell 
Cliffs,  Hants.  Everywhere  Planorbis  euomphalus,  fig.  192.,  charac- 
terizes the  freshwater  deposits,  just  as  the  allied  form,  P.  discus, 
fig.  187.,  does  the  Bembridge  limestone.  The  brackish-water  beds 
contain  Potomomya  plana,  Cerithium  mutabile,  and  C.  cinctum 
(fig.  44.  p.  30.),  and  the  marine  beds  Venus  (or  Cythered]  incrassata, 
a  species  common  to  the  Limburg  beds  and  Gres  de  Fontainebleau, 
or  the  Upper  Eocene  series.  The  prevalence  of  salt-water  remains 

p  2 


212 


SHELLS   OF    THE   HEADON    SERIES. 


[On.  XVI. 


is  most  conspicuous  in  some  of  the  central  parts  of  the  formation. 
Mr.  T.  Webster,  in   his  able  memoirs  on  the  Isle  of  Wight,   first 


Fig.  192. 


Fig.  193. 


Planorbis  euomphalus,  Sow. 
Headon  Hill.    |  diam. 


Helix  labyrinthica.  Say.     Headon  Hill,  Isle  of  Wight ; 
and  Hordwell  Cliff,  Hants —also  recent. 


separated  the  whole  into  a  lower  freshwater,  an  upper  marine,  and  an 
upper  freshwater  division. 

Among  the  shells  which  are  widely  distributed  through  the  Headon 
series  are  Neritina  concava,  (fig.194.),  Lymnea  caudata  (fig.  195.),  and 
Cerithium  concavum  (fig.  196.).  Helix  labyrinthica^  Say  (fig.  193.), 


Fig.  194. 


Fig.  195. 


Fig.  196. 


Neritina  concava. 
Headon  Series. 


Lymnea  caudata. 
Headon  Beds. 


Cerithium  concavum 
Headon  Series. 


a  land-shell  now  inhabiting  the  United  States,  was  discovered  in  this 
series  by  Mr.  Wood  in  Hordwell  Cliff.  It  is  also  met  with  in  Headon 
Hill,  in  the  same  beds.  At  Sconce,  in  the  Isle  of  Wight,  it  occurs 
in  the  newer  Bembridge  series,  and  affords  a  rare  example  of  an 
Eocene  fossil  of  a  species  still  living,  though,  as  usual  in  such  cases, 
having  no  local  connexion  with  the  actual  geographical  range  of  the 
species. 

The  lower  and  middle  portion  of  the  Headon  series  is  also  met 
with  in  Hordwell  Cliff  (or  Hordle,  as  it  is  often  spelt),  near  Ly- 
mington,  Hants,  where  the  organic  remains  have  been  studied  by  Mr. 
Searles  Wood,  Dr.  Wright,  and  the  Marchioness  of  Hastings.  To  the 
latter  we  are  indebted  for  a  detailed  section  of  the  beds  *,  as  well  as 
for  the  discovery  of  a  variety  of  new  species  of  fossil  mammalia, 
chelonians,  and  fish  ;  also  for  first  calling  attention  to  the  important 
fact  that  these  vertebrata  differ  specifically  from  those  of  the  Bem- 
bridge beds.  Among  the  abundant  shells  of  Hordwell  are  Paludina 
lenta  and  various  species  of  Lymneus,  Planorbis,  Melania,  Cyclas,  and 
Unio,  Potomomya,  Dreissena,  &c. 


*  Bulletin  Soc.  Geol.  de  France,  1852,  p.  191. 


OH.  XVI.]       FLUVIO-MARINE    SERIES   IN    HAMPSHIRE.  213 

Among  the  chelonians  we  find  a  species  of  JEmys,  and  no  less  than 
six  species  of  Trionyx ;  among  the  saurians  an  alligator  and  a 
crocodile;  among  the  ophidians  two  species  of  land-snakes  (Pa- 
leryx,  Owen) ;  and  among  the  fish  Sir  P.  Egerton  and  Mr.  Wood 
have  found  the  jaws,  teeth,  and  hard  shining  scales  of  the  genus 
Lepidosteus  or  bony  pike  of  the  American  rivers.  This  same  genus 
of  freshwater  ganoids  has  also  been  met  with  in  the  Hempstead  beds 
in  the  Isle  of  Wight.  The  bones  of  several  birds  have  been  ob- 
tained from  Hordwell,  and  the  remains  of  quadrupeds.  The  latter 
belong  to  the  genera  Paloplotherium  of  Owen,  Anoplotherium, 
Anthracotherium,  Dichodon  of  Owen  (a  new  genus  discovered  by 
Mr.  A.  H.  Falconer),  Dichobune,  Spalacodon,  and  Hycenodon.  The 
latter  offers,  I  believe,  the  oldest  known  example  of  a  true  carni- 
vorous mammal  in  the  series  of  British  fossils,  although  I  attach  very 
little  theoretical  importance  to  the  fact,  because  herbivorous  species 
are  those  most  easily  met  with  in  a  fossil  state  in  all  save  cavern 
deposits.  In  another  point  of  view,  however,  this  fauna  deserves 
notice.  Its  geological  position  is  considerably  lower  that  that  of  the 
Bembridge  or  Montmartre  beds,  from  which  it  differs  almost  as  much 
in  species  as  it  does  from  the  still  more  ancient  fauna  of  the  Lower 
Eocene  beds  to  be  mentioned  in  the  sequel.  It  therefore  teaches  us 
what  a  grand  succession  of  distinct  assemblages  of  mammalia  flou- 
rished on  the  earth  during  the  Eocene  period. 

Many  of  the  marine  shells  of  the  brackishwater  beds  of  the 
above  series,  both  in  the  Isle  of  Wight  and  Hordwell  Cliff,  are 
common  to  the  underlying  Barton  clay ;  and,  on  the  other  hand,  there 
are  some  freshwater  shells,  such  as  Cyrena  obovata,  which  are 
common  to  the  Bembridge  beds,  notwithstanding  the  intervention  of 
the  St.  Helen's  series.  The  white  and  green  marls  of  the  Headon 
series,  and  some  of  the  accompanying  limestones,  often  resemble  the 
Eocene  strata  of  France  in  mineral  character  and  colour  in  so 
striking  a  manner,  as  to  suggest  the  idea  that  the  sediment  was 
derived  from  the  same  region  or  produced  contemporaneously  under 
very  similar  geographical  circumstances. 

Both  in  Hordwell  Cliff  and  in  the  Isle  of  Wight,  the  Headon  beds 
rest  on  white  sands,  the  upper  member  of  the  Barton  series,  B.  4., 
next  to  be  mentioned. 

Headon  Hill  sands  and  Barton  clay,  B.   4.  (Table,  p.  209.)  — - 
Fig.  197.       In  one  of  the  upper  and  sandy  beds  of  this  formation 
Dr.  Wright  found  Chama  squamosa  in  great  plenty. 
^ne  same  sands  contain  impressions  of  many  marine 
shells  (especially  in  Whitecliff  Bay)  common  to  the 
upper  Bagshot  sands  afterwards  to  be  described.     The 
underlying  Barton  clay  has  yielded  about  209  marine 
shells,  more  than  half  of  them,  according  to  Mr.  Prest- 
wich,  peculiar ;  and  only  eleven  common  to  the  London 
Chama  squamosa.  clayproper,  (C.I.  p.  209.,)  being  in  the  proportion  of  only 
Barton.        5  per  cenf;.     Qn  the  other  hand,  70  of  them  agree  with 
the  shells  of  the  calcaire  grassier  of  France.     It  is  nearly  a  century 

p  3 


214 


FOSSILS   OF    THE    BARTON   CLAY. 


[Cn.  XVI. 


since  Brander  published,  in  1766,  an  account  of  the  organic  remains 
collected  from  these  Barton  and  Hordwell  cliffs,  and  his  excellent 
figures  of  the  shells  then  deposited  in  the  British  Museum  are  justly 
admired  by  conchologists  for  their  accuracy. 

SHELLS  OF  THE  BARTON  CLAY,  HANTS. 

Certain   foraminifera  called  Nummulites  begin,  when  we  study 
the  tertiary  formations  in  a  descending  order,  to  make  their  first 


Fig.  198. 


Fig.  199. 


Fig.  200. 


Fig.  201. 


Mitrascabra.  Valuta  ambigua.  Typhis  pungens.  Valuta  athleta.    Barton 

and  Braklesham. 


Fig.  202. 


Fig.  203. 


Fig.  204. 


Fig.  205. 


Terebettumfusi-        Terebellum  con- 
forme.    Barton          volutum,  Lam. 
and  Bracklesham.    Seraphs  convolu- 
tum,  Montf. 


Cardita  globosa. 


Crassatella  sulcata. 


appearance  in  these  Barton  beds.  A  small  species  called  Nummulites 
variolaria  is  found  both  on  the  Hampshire  coast  and  in  beds  of  the 
same  age  in  Whitecliff  Bay,  in  the  Isle  of  Wight.  Several  marine 
shells,  such  as  Corbula  pisum,  are  common  to  the  Barton  beds  and 
the  Hempstead  or  Upper  Eocene  series,  and  a  still  greater  number, 
as  before  stated,  are  common  to  the  Headon  series. 

Bagshotand  Bracklesham  beds,  B.  5. — TheBagshot  beds,  consisting 
chiefly  of  siliceous  sand,  occupy  extensive  tracts  round  Bagshot,  in 
Surrey,  and  in  the  New  Forest,  Hampshire.  They  may  be  separated 
into  three  divisions,  the  upper  and  lower  consisting  of  light  yellow 
sands,  and  the  central  of  dark  green  sands  and  brown  clays,  the  whole 
reposing  on  the  London  clay  proper.*  The  uppermost  division  is 
probably  of  about  the  same  age  as  the  Barton  series.  Although 


*  Prestwich,  Quart.  Geol.  Journ.  vol.  iii.  p.  386. 


CH.  XVI.]        EOCENE  — BAGSHOT  SANDS.  215 

the  Bagshot  beds  are  usually  devoid  of  fossils,  they  contain  marine 
shells  in  some  places,  among  which  Venericardia  planicosta  (see  fig. 

Fig.  206. 


Venericardia  planicosta,  Lam* 
Car dita  planicosta,  Deshayes. 

206.)  is  abundant,  with   Turritella  sulcifera  and  Nummulites  Icevi- 
gata.     (See  fig.  210.  p.  216.). 

At  Bracklesham  Bay,  near  Chichester,  in  Sussex,  the  characteristic 
shells  of  this  member  of  the  Eocene  series  are  best  seen;  among 
others,  the  huge  Cerithium  giganteum,  so  conspicuous  in  the  calcaire 
grossier  of  Paris,  where  it  is  sometimes  2  feet  in  length.  The 
volutes  and  cowries  of  this  formation,  as  well  as  the  lunulites 
and  corals,  seem  to  favour  the  idea  of  a  warm  climate  having  pre- 
vailed, which  is  borne  out  by  the  discovery  of  a  serpent,  Palceophis 
typhceus  (see  fig.  207.),  exceeding,  according  to  Prof.  Owen,  20  feet 

Fig.  207. 


Palecophis  typheeus,  Owen  ;  an  Eocene  sea-serpent.    Bracklesham. 
a.  6.  vertebra,  with  long  neural  spine  preserved.  c.  two  vertebra  in  natural  articulation. 

in  length,  and  allied  in  its  osteology  to  the  Boa,  Python,  Coluber,  and 
Hydrus.  The  compressed  form  and  diminutive  size  of  certain  caudal 
vertebras  indicate  so  much  analogy  with  Hydrus  as  to  induce  the 
Hunterian  professor  to  pronounce  this  extinct  ophidian  to  have  been 
marine.*  He  had  previously  combated  with  much  success  the  evi- 
dence advanced  to  prove  the  existence  in  the  Northern  Ocean  of 
huge  sea-serpents  in  our  own  times,  but  he  now  contends  for  the 
former  existence  in  the  British  Eocene  seas,  of  less  gigantic  serpents, 


*  Palseont.  Soc.  Monograph.  Kept.  pt.  ii.  p.  61. 
p  4 


216  BRACKLESHAM    BEDS.  [Cn.  XVI. 

when  the  climate  was  probably  more  genial ;  for  amongst  the  com- 
panions of  the  sea-snake  of  Bracklesham  was  an  extinct  Gavial 
(  Gavialis  Dixoni,  Owen),  and  numerous  fish,  such  as  now  frequent 
the  seas  of  warm  latitudes,  as  the  sword-fish  (see  fig.  208.),  and 
gigantic  rays  of  the  genus  Myliobates  (see  fig.  209.). 

Fig.  208. 


Prolonged  premaxillary  bone  or  "  sword  "  of  a  fossil  sword-fish  (Ccelorhynchus).    Brackle- 
sham.   Dixon's  Fossils  of  Sussex,  pi.  8. 

Fig.  209.  Fig.  210. 

X?^lK 

6 


Dental  plates  of  Myliobates  Edwardsi. 
Bracklesham  Bay-    Ibid.  pi.  8. 


Nummulites  (Nummularfa)  Itevigata 
Bracklesham.     Ibid.  pi.  8. 

a.  section  of  the  nummnlite. 

b.  group,  with  an  individual  showing  the  exterior 

of  the  shell. 


The  teeth  of  sharks  also,  of  the  genera  Carcharodon,  Otodus,  Lamna, 
Galeocerdo,  and  others,  are  abundant.    (See  figs.  211,  212,  213,  214.) 


Fig.  211. 


Fig.  212. 


Fig.  213. 


Fig.  214. 


Carcharodon  keterodon,  Agass. 


Otodzis  obliquus,  Agass.        Lamna  elegans,       Galeocerdo  latideni 

Agass.  Agass. 

Teeth  of  sharks  from  Bracklesham  Bay. 


The  Nummulites  Itzvigata  (see  fig.  210.),  so  characteristic  of  the  lower 
beds  of  the  calcaire  grossier  in  France,  where  it  sometimes  forms 
stony  layers,  as  near  Compiegne,  is  very  common  at  Bracklesham,  toge- 
ther with  N.  scabra  and  N.  variolaria.  Out  of  193  species  of  testacea 
procured  from  the  Bagshot  and  Bracklesham  beds  in  England,  126  occur 
in  the  calcaire  grossier  in  France.  It  was  clearly  therefore  coeval  with 
that  part  of  the  Parisian  series  more  nearly  than  with  any  other. 


OH.  XVI.]      LOWER   EOCENE    STRATA   OF   ENGLAND.  217 

MARINE    SHELLS   OP   BRACKLESHAM   BEDS. 
Fig.  215.  Fig.  216.  Fig.  217.  Fig.  218.  Fig.  219. 


Pleurotoma  attenuata,    Valuta  la~ 
Sow.  trella,  Lam. 


TurrtteUa, 
multisulcata, 
Lam. 


Lucina  serrata,  Dixon. 
Magnified. 


Conus  deper- 
ditus. 


LOWER   EOCENE    FORMATIONS   OF   ENGLAND. 

London  Clay  proper  (C.  1.  Table,  p.  209.). —  This  formation  under- 
lies the  preceding,  and  consists  of  tenacious  brown  and  bluish-gray 
clay,  with  layers  of  concretions  called  septaria,  which  abound  chiefly 
in  the  brown  clay,  and  are  obtained  in  sufficient  numbers  from  sea- 
cliffs  near  Harwich,  and  from  shoals  off  the  Essex  coast,  to  be  used 
for  making  Roman  cement.  The  principal  localities  of  fossils  in  the 
London  clay  are  Highgate  Hill,  near  London,  the  island  of  Sheppey, 
and  Bognor  in  Hampshire.  Out  of  133  fossil  shells,  Mr.  Prestwich 
found  only  20  to  be  common  to  the  calcaire  grossier  (from  which  600 
species  have  been  obtained),  while  33  are  common  to  the  "  Lits  Co- 
quilliers  "  (p.  229.),  in  which  only  200  species  are  known  in  France. 
We  may  presume,  therefore,  that  the  London  clay  proper  is  older 
than  the  calcaire  grossier.  This  may  perhaps  remove  a  difficulty 
which  M.  Adolphe  Brongniart  has  experienced  when  comparing  the 
Eocene  Flora  of  the  neighbourhoods  of  London  and  Paris.  The 
fossil  species  of  the  island  of  Sheppey,  he  observes,  indicate  a  much 
more  tropical  climate  than  the  Eocene  Flora  of  France.  Now  the 
latter  has  been  derived  principally  from  the  gypseous  series,  and  resem- 
bles the  vegetation  of  the  borders  of  the  Mediterranean  rather  than 
that  of  an  equatorial  region;  whereas  the  older  flora  of  Sheppey 
Fig.  220.  belongs  to  an  antecedent  epoch,  separated 

from  the  period  of  the  Paris  gypsum  by 
all  the  calcaire  grossier  and  Bagshot  series  — 
in  short,  by  the  whole  nummulitic  formation 
properly  so  called. 

Mr.  Bowerbank,  in  a  valuable  publication 
on  the  fossil  fruits  and  seeds  of  the  island  of 
Sheppey,  near  London,  has  described  no  less 
than  thirteen  fruits  of  palms  of  the  recent 
type  Nipa,  now  only  found  in  the  Molucca 
and  Philippine  islands  and  in  Bengal  (see 
fig.  220.).     In  the  delta  of  the  Ganges,  Dr. 
*   sil  Hooker  observed  the   large  nuts   of  Nipa 
fruticans    floating  in  such  numbers  in  the 
various  arms  of  that  great  river,  as  to  obstruct  the  paddle-wheels  of 


218  FOSSILS   OF    THE   LONDON   CLAY.  [Cn.  XVI. 

steam-boats.  These  plants  are  allied  to  the  cocoa-nut  tribe  on  the  one 
side,  and  on  the  other  to  the  Pandanus,  or  screw-pine.  The  fruits 
of  other  palms  besides  those  of  the  cocoa-nut  tribe  are  also  met  with 
in  the  clay  of  Sheppey ;  also  three  species  of  Anona^  or  custard 
apple  ;  and  cucurbitaceous  fruits  (of  the  gourd  and  melon  family)  are 
in  considerable  abundance.  Fruits  of  various  species  of  Acacia  are  in 
profusion,  and  these,  although  less  decidedly  tropical,  imply  a  warm 
climate. 

The  contiguity  of  land  may  be  inferred  not  only  from  these  vege- 
table productions,  but  also  from  the  teeth  and  bones  of  crocodiles  and 
turtles,  since  these  creatures,  as  Dr.  Conybeare  has  remarked,  must 
have  resorted  to  some  shore  to  lay  their  eggs.  Of  turtles  there  were 
numerous  species  referred  to  extinct  genera.  These  are,  for  the  most 
part,  not  equal  in  size  to  the  largest  living  tropical  turtles.  A  sea- 
snake,  which  must  have  been  13  feet  long,  of  the  genus  Palaophis 
before  mentioned  (p.  2 15.),  has  also  been  described  by  Prof.  Owen  from 
Sheppey,  of  a  different  species  from  that  of  Bracklesham.  A  true  croco- 
dile, also,  Crocodilus,  toliapicus,  and  another  saurian  more  nearly  allied 
to  the  gavial,  accompany  the  above  fossils ;  also  the  relics  of  several 
birds  and  quadrupeds.  One  of  these  last  belongs  to  the  new  genus 
Hyracotherium  of  Owen,  allied  to  the  Hyrax,  Hog,  and  Chasropo- 
tamus  ;  another  is  a  Lophiodon;  a  third,  a  pachyderm  called  Cory- 
phodon  eoccenus  by  Owen,  larger  than  any  existing  tapir.  All  these 
animals  seem  to  have  inhabited  the  banks  of  the  great  river  which 
floated  down  the  Sheppey  fruits.  They  imply  the  existence  of  a 
mammiferous  fauna  antecedent  to  the  period  when  nummulites 
flourished  in  Europe  and  Asia,  and  therefore  before  the  Alps, 
Pyrenees,  and  other  mountain-chains  now  forming  the  backbones  of 
great  continents,  were  raised  from  the  deep ;  nay,  even  before  a  part 
of  the  constituent  rocky  masses  now  entering  into  the  central  ridges 
of  these  chains  had  been  deposited  in  the  sea. 

The  marine  shells  of  the  London  clay  confirm  the  inference  de- 
rivable from  the  plants  and  reptiles  in  favour  of  a  high  temperature. 
Thus  many  species  of  Conns  and  Valuta  occur,  a  large  Cypr&a, 
C.  oviformis,  a  very  large  Rostellaria,  (fig.  223.),  a  species  of  Cancel- 
laria,  six  species  of  Nautilus  (fig.  225.),  besides  other  cephalopoda 
of  extinct  genera,  one  of  the  most  remarkable  of  which  is  the 
Belosepia*  (fig.  226.)  Among  many  characteristic  bivalve  shells  are 
Leda  amygdaloides  (fig.  227.)  and  Axinus  angulatus  (fig.  228.),  and 
among  the  Radiata  a  star-fish  called  Astropecten  (fig.  229.). 

These  fossils  are  accompanied  by  a  sword-fish  (  Tetrapterus  pris- 
cus,  Agassiz),  about  8  feet  long,  and  a  saw-fish  (Pristis  bisulcatus, 
Ag-X  about  10  feet  in  length  ;  genera  now  foreign  to  the  British 
seas.  On  the  whole,  no  less  than  50  species  of  fish  have  been  de- 
scribed by  M.  Agassiz  from  these  beds  in  Sheppey,  and  they  indicate, 
in  his  opinion,  a  warm  climate. 

*  For  description  of  Eocene  Cephalopoda,  see  Monograph  by  F.  E.  Edwards, 
PaUeontograph.  Soc.  1849. 


CH.  XVI.]      FOSSIL   SHELLS  OF   THE  LONDON  CLAY.  219 

FOSSIL    SHELLS   OF   THE   LONDON   CLAY. 


Fig.  221. 


Fig.  222. 


Valuta  nodosa,  Sow.         Phorus  extensus, 
Highgate.  Sow.    Highgate. 

Fig.  224. 


Nautilus  centralis,  Sow.    Highgate. 


Fig.  225. 


Aturia  zi'czac,  Brown  and  Edwards. 
Syn.  Nautilus  ziczac,  Sow. 
London  clay.    Sheppey. 


Fig.  227* 


Fig.  223. 


Rostettaria  macroptera,  Sow.    One-third 
of  nat.  size ;  also  found  in  the  Barton  clay. 


Fig.  226. 


Fig.  228. 


Belosepia  sepioidea.  De  Blainv. 
London  clay.    Sheppey. 


Fig.  229. 


Leda  amygdaloides. 
Highgate. 


Axinus  fngulatus.    London 
clay.    Hornsea. 


Astropecten  crispatus, 
E.  Forbes.    Sheppey. 


Strata  of  Kyson  in  Suffolk.  —  At  Kyson,  a  few  miles  east  of 
Woodbridge,  a  bed  of  Eocene  clay,  12  feet  thick,  underlies  the  red 
crag.  Beneath  it  is  a  deposit  of  yellow  and  white  sand,  of  con- 
siderable interest,  in  consequence  of  many  peculiar  fossils  contained 
in  it.  Its  geological  position  is  probably  the  lowest  part  of  the 


220  STRATA   OF    KYSON   IN   SUFFOLK.  [Cn.  XVI. 

London  clay  proper.  In  this  sand  has  been  found  the  first  example 
of  a  fossil  quadrumanous  animal  discovered 
in  Great  Britain,  namely,  the  teeth  and  part 
°^  a  Jaw'  sbown  ky  Prof.  Owen  to  belong 
to  a  monkey  of  the  genus  Macacus  (see  fig. 
Molar  of  monkey  (Macacus).  2300'  The  mammiferous  fossils,  first  met 
with  in  the  same  bed,  were  those  of  an 

opossum  (Didelphys)  (see  fig.  231.),  and  an  insectivorous  bat  (fig. 
232.),  together   with  many  teeth   of  fishes   of  the   shark   family. 
Fig.  23i.  Mr.  Colchester  in    1840   obtained   other 

mammalian  relics  from  Kyson,  among 
which  Prof.  Owen  has  recognized  several 
teeth  of  the  genus  Hyracotherium,  and 
the  vertebrae  of  a  large  serpent,  probably 
a  Palcp.ophis.  As  the  remains  both  of 

Motor  tooth  andput  of Jawof  opossum.  ^    ^yracotherium   and    PaltBOphlS   WGTG 

Fig  232  afterwards  met  with  in  the  London  clay, 

A  as   before   remarked,   these   fossils   con- 

firmed the  opinion  previously  entertained, 
that  the  Kyson  sand  belongs  to  the  Eocene 
period.     The   Macacus,    therefore,  con- 
Molars  of  insectivorous  bats,        stitutes  the  first  example  of  any  quadru- 
From  Ky?oan,'  Suffolk.  manous  animal  occurring  in  strata  so  old 

as  the  Eocene,  or  in  a  spot  so  far  from  the 

equator  as  lat  52°  N.  It  was  not  until  after  the  year  1836  that  the 
existence  of  any  fossil  quadrumana  was  brought  to  light.  Since  that 
period  they  have  been  discovered  in  France,  India,  and  Brazil. 

Plastic  or  mottled  clays  and  sands  (C.  2.  p.  209.). —  The  clays 
called  plastic,  which  lie  immediately  below  the  London  clay,  received 
their  name  originally  in  France  from  being  often  used  in  pottery. 
Beds  of  the  same  age  (the  Woolwich  and  Reading  series  of  Prest- 
wich)  are  used  for  the  like  purposes  in  England,  j- 

No  formations  can  be  more  dissimilar  on  the  whole  in  mineral  cha- 
racter than  the  Eocene  deposits  of  England  and  Paris ;  those  of  our 
own  island  being  almost  exclusively  of  mechanical  origin,  —  accumu- 
lations of  mud,  sand,  and  pebbles ;  while  in  the  neighbourhood  of 
Paris  we  find  a  great  succession  of  strata  composed  of  limestones, 
some  of  them  siliceous,  and  of  crystalline  gypsum  and  siliceous  sand- 
stone, and  sometimes  of  pure  flint  used  for  millstones.  Hence  it  is  by 
no  means  an  easy  task  to  institute  an  exact  comparison  between  the 
various  members  of  the  English  and  French  series,  and  to  settle 
their  respective  ages.  It  is  clear  that,  on  the  sites  both  of  Paris  and 
London,  a  continual  change  was  going  on  in  the  fauna  and  flora  by 
the  coming  in  of  new  species  and  the  dying  out  of  others ;  and 
contemporaneous  changes  of  geographical  conditions  were  also  in 
progress  in  consequence  of  the  rising  and  sinking  of  the  land  and 
bottom  of  the  sea.  A  particular  subdivision,  therefore,  of  time  was 

*  Annals  of  Nat.  Hist.  vol.  iv.  No.  23.  Nov.  1839. 
f  Prestwich,  Wate»bearing  Strata  of  London,  1851. 


CH.  XVI.]   LOWER  EOCENE  STRATA  OF  ENGLAND. 


221 


occasionally  represented  in  one  area  by  land,  in  another  by  an  estuary, 
in  a  third  by  the  sea,  and  even  where  the  conditions  were  in  both 
areas  of  a  marine  character,  there  was  often  shallow  water  in  one, 
and  deep  sea  in  another,  producing  a  want  of  agreement  in  the  state 
of  animal  life. 

But  in  regard  to  that  division  of  the  Eocene  series  which  we  have 
now  under  consideration,  we  find  an  exception  to  the  general  rule, 
for,  whether  we  study  it  in  the  basins  of  London,  Hampshire,  or 
Paris,  we  recognize  everywhere  the  same  mineral  character.  This 
uniformity  of  aspect  must  be  seen  in  order  to  be  fully  appreciated, 
since  the  beds  consist  simply  of  sand,  mottled  clays,  and  well-rolled 
flint  pebbles,  derived  from  the  chalk,  and  varying  in  size  from  that  of 
a  pea  to  an  egg.  These  strata  may  be  seen  in  the  Isle  of  Wight 
in  contact  with  the  chalk,  or  in  the  London  basin,  at  Reading, 
Blackheath,  and  Woolwich.  In  some  of  the  lowest  of  them,  banks  of 
oysters  are  observed,  consisting  of  Ostrea  bellovacina,  so  common 
in  France  in  the  same  relative  position,  and  Ostrea  edulina,  scarcely 
distinguishable  from  the  living  eatable  species.  In  the  same  beds  at 
Bromley,  Dr.  Buckland  found  one  large  pebble  to  which  five  full- 
grown  oysters  were  affixed,  in  such  a  manner  as  to  show  that  they 
had  commenced  their  first  growth  upon  it,  and  remained  attached  to 
it  through  life. 

In  several  places,  as  at  Woolwich  on  the  Thames,  at  Newhaven  in 
Sussex,  and  elsewhere,  a  mixture  of  marine  and  freshwater  testacea 
distinguishes  this  member  of  the  series.  Among  the  latter,  Melania 
inquinata  (see  fig.  234.)  and  Cyrena  cuneiformis  (see  fig.  233.)  are 


Fig.  233. 


Fig.  234. 


Cyrena  cuneiformis,  Win.  Con. 
Natural  size. 


Melania  inquinata,  Des.    Nat.  size. 
Syn.  Cerithium  melnnoides,  Min.  Con. 


very  common,  as  in  beds  of  corresponding  age  in  France.  They 
clearly  indicate  points  where  rivers  entered  the  Eocene  sea.  Usually 
there  is  a  mixture  of  brackish,  freshwater,  and  ma^rine  shells,  and 


222  PLASTIC    CLAYS   AND   SANDS.  [Cn.  XVI. 

sometimes,  as  at  Woolwich,  proofs  of  the  river  and  the  sea  having 
successively  prevailed  on  the  same  spot.  At  New  Charlton,  in  the 
suburbs  of  Woolwich,  Mr.  De  la  Condamine  discovered  in  1849,  and 
pointed  out  to  me,  a  layer  of  sand  associated  with  well-rounded  flint 
pebbles  in  which  numerous  individuals  of  the  Cyrena  tellinella  were 
seen  standing  endwise  with  both  their  valves  united,  the  posterior 
extremity  of  each  shell  being  uppermost,  as  would  happen  if  the 
inollusks  had  died  in  their  natural  position.  I  have  described*  a 
bank  of  sandy  mud,  in  the  delta  of  the  Alabama  river  at  Mobile,  on 
the  borders  of  the  Gulf  of  Mexico,  where  in  1846  I  dug  out  at  low 
tide  specimens  of  living  species  of  Cyrena  and  of  a  Gnathodon,  which 
were  similarly  placed  with  their  shells  erect,  or  in  a  position  which 
enables  the  animal  to  protrude  its  siphon  upwards,  and  draw  in  or 
reject  water  at  pleasure.  The  water  at  Mobile  is  usually  fresh,  but 
sometimes  brackish.  At  Woolwich  a  body  of  river-water  must  have 
flowed  permanently  into  the  sea  where  the  Cyrence  lived,  and  they 
may  have  been  killed  suddenly  by  an  influx  of  pure  salt  water,  which 
invaded  the  spot  when  the  river  was  low,  or  when  a  subsidence  of 
land  took  place.  Traced  in  one  direction,  or  eastward  towards 
Herne  Bay,  the  Woolwich  beds  assume  more  and  more  of  a  marine  cha- 
racter ;  while  in  an  opposite,  or  south-western  direction,  they  become, 
as  near  Chelsea  and  other  places,  more  freshwater,  and  contain  Unio, 
Paludinct)  and  layers  of  lignite,  so  that  the  land  drained  by  the  ancient 
river  seems  clearly  to  have  been  to  the  south-west  of  the  present  site 
of  the  metropolis. 

Before  the  minds  of  geologists  had  become  familiar  with  the 
theory  of  the  gradual  sinking  of  land,  and  its  conversion  into  sea 
at  different  periods,  and  the  consequent  change  from  shallow  to  deep 
water,  the  freshwater  and  littoral  character  of  this  inferior  group 
appeared  strange  and  anomalous.  After  passing  through  hundreds  of 
feet  of  London  clay,  proved  by  its  fossils  to  have  been  deposited  in 
deep  salt  water,  we  arrive  at  beds  of  fluviatile  origin,  and  in  the 
same  underlying  formation  masses  of  shingle,  attaining  at  Black- 
heath,  near  London,  a  thickness  of  50  feet,  indicate  the  proximity  of 
land,  where  the  flints  of  the  chalk  were  rolled  into  sand  and  pebbles, 
and  spread  continuously  over  wide  spaces.  Such  shingle  always 
appears  at  the  bottom  of  the  series,  whether  in  the  Isle  of  Wight,  or 
in  the  Hampshire  or  London  basins.  It  may  be  asked  why  they  did 
not  constitute  simply  narrow  littoral  zones,  such  as  we  might  look 
for  on  an  ancient  sea-shore.  In  reply,  Mr.  Prestwich  has  suggested 
that  such  zones  of  shingle  may  have  been  slowly  formed  on  a  large 
scale  at  the  period  of  the  Thanet  sands  (C.  3.  p.  209.),  and  while  the 
land  was  sinking  the  well-rolled  pebbles  may  have  been  dispersed 
simultaneously  over  considerable  areas,  and  exposed  during  gradual 
submergence  to  the  action  of  the  waves  of  the  sea,  aided  occasionally 
by  tidal  currents  and  river  floods. 

Thanet  sands  (C.  3.  p.  209.).  —  The  mottled  or  plastic  clay  of  the 

*  Second  Visit  to  the  United  States,  vol.  ii.  p.  104. 


CH.  XVI.]  EOCENE    STRATA    IN    FIIANCE.  223 

Isle  of  Wight  and  Hampshire  is  often  seen  in  actual  contact  with 
the  chalk,  constituting  in  such  places  the  lowest  member  of  the 
British  Eocene  series.  But  in  other  points  another  formation  of 
marine  origin,  characterized  by  a  somewhat  different  assemblage  of 
organic  remains,  has  been  shown  by  Mr.  Prestwich  to  intervene 
between  the  chalk  and  the  Woolwich  series.  For  these  beds  he  has 
proposed  the  name  of  "  Thanet  Sands,"  because  they  are  well  seen  in 
the  Isle  of  Thanet,  in  the  northern  part  of  Kent,  and  on  the  sea-coast 
between  Herne  Bay  and  the  Reculvers,  where  they  consist  of  sands 
with  a  few  concretionary  masses  of  sandstone,  and  contain  among 
other  fossils  Pholadomya  cuneata,  Cyprina  Morrisii,  Corbula  longi- 
rostris,  Scalaria  Bowerbankii,  &c.  The  greatest  thickness  of  these 
beds  is  about  90  feet. 

FRENCH   MIDDLE   EOCENE   FORMATIONS. 

GENERAL   TABLE   OF   FRENCH   EOCENE    STRATA. 

A.     UPPER  EOCENE  (Lower  Miocene  of  many  French  authors). 

English  Equivalents. 

A.  Calcaire  dc  la  Bcauce,  or  upper  fresh-  -j 

water,  see  p.  185.,  and  Gres  de  Fon-  I  Hempstead  series,  see  p.  193. 
tainebleau,  &c.  J 

B.      MIDDLE   EOCENE. 

B.  1.  Gypseous  series  and  Middle    fresh-  j  Bembrid     geri 

water  calcaire  lacustre  moyen.  J 


B.  2.  Calcaire  siliceux,  (in  part  contem- T  Lower  rf     ^    Bcmbrid 

TWriTlPOri"       •»"^*«         +Ka       cn/»/»ooriinnr     > 

group  ?) 


poraneous    with     the    succeeding  j-      geneg< 


{Osborne  series,  and  upper  and  middle 
part  of   Headon  series,  Isle    of 
Wight. 
^       .       /ri  .,       N  -I  Headon  Hill  Sands,  Barton,  Upper 

"•  4'      PPTM  ST  I       T  (  }  \      BaSshot  ««4  part  of  Bracilesham 

and  Middle  Calcaire  Grossier.  bc(fs 

B.  5.  Lower    Calcaire  Grossier   or    Glau-  -j 

.    ~  }•  Bracklesham  beds. 

come  Grossiere.  J 

i  Lower  Bagshot.    Intermediate  in  age 

B.  6.  Soissonuais  Sans  or  Litscoquilliers.  <      between  the  Bracklesham  beds  and 

C     London  Clay 

C.      LOWER  EOCENE. 


0.  Argileplastiqueet  lignite.  (P1^c  flay  and    sand,  with  lignite 

I     (Woolwich  and  Reading  series). 

The  tertiary  formations  in  the  neighbourhood  of  Paris  consist  of  a 
series  of  marine  and  freshwater  strata,  alternating  with  each  other, 
and  filling  up  a  depression  in  the  chalk.  The  area  which  they 
occupy  has  been  called  the  Paris  basin,  and  is  about  180  miles  in  its 
greatest  length,  from  north  to  south,  and  about  90  miles  in  breadth 
from  east  to  west  (see  Map,  p.  196.).  MM.  Cuvier  and  Brongniart 
attempted,  in  1810,  to  distinguish  five  different  groups,  comprising 


224         MIDDLE   AND   LOWER    EOCENE    OP    FRANCE.       [Cn.  XVI. 

three  freshwater  and  two  marine,  which  were  supposed  to  imply  that 
the  waters  of  the  ocean,  and  of  rivers  and  lakes,  had  been  by  turns 
admitted  into  and  excluded  from  the  same  area.  Investigations 
since  made  in  the  Hampshire  and  London  basins  have  rather  tended 
to  confirm  these  views,  at  least  so  far  as  to  show,  that  since  the 
commencement  of  the  Eocene  period  there  have  been  great  move- 
ments of  the  bed  of  the  sea,  and  of  the  adjoining  lands,  and  that  the 
superposition  of  deep  sea  to  shallow  water  deposits  (the  London 
clay,  for  example,  to  the  Woolwich  beds)  can  only  be  explained  by 
referring  to  such  movements.  Nevertheless,  it  appears,  from  the 
researches  of  M.  Constant  Prevost,  that  some  of  the  alternations  and 
intermixtures  of  freshwater  and  marine  deposits,  in  the  Paris  basin, 
may  be  accounted  for  by  imagining  both  to  have  been  simultaneously 
in  progress,  in  the  same  bay  of  the  same  sea,  or  a  gulf  into  which 
many  rivers  entered. 

To  enlarge  on  the  numerous  subdivisions  of  the  Parisian  strata, 
would  lead  me  beyond  my  present  limits ;  I  shall  therefore  give 
some  examples  only  of  the  most  important  formations  enumerated  in 
the  foregoing  Table,  p.  223. 

Beneath  the  Upper  Eocene  or  "  Upper  marine  sands,"  A,  already 
spoken  of,  (p.  195.),  we  find,  in  the  neighbourhood  of  Paris,  a 
series  of  white  and  green  marls,  with  subordinate  beds  of  gypsum,  B. 
These  are  most  largely  developed  in  the  central  parts  of  the  Paris 
basin,  and,  among  other  places,  in  the  Hill  of  Montmartre,  where  its 
fossils  were  first  studied  by  M.  Cuvier. 

The  gypsum  quarried  there  for  the  manufacture  of  plaster  of  Paris 
occurs  as  a  granular  crystalline  rock,  and,  together  with  the  associated 
marls,  contains  land  and  fluviatile  shells,  together  with  the  bones  and 
skeletons  of  birds  and  quadrupeds.  Several  land  plants  are  also  met 
with,  among  which  are  fine  specimens  of  the  fan  palm  or  palmetto  tribe 
(Flabellaria).  The  remains  also  of  freshwater  fish,  and  of  crocodiles 
and  other  reptiles,  occur  in  the  gypsum.  The  skeletons  of  mammalia 
are  usually  isolated,  often  entire,  the  most  delicate  extremities  being 
preserved ;  as  if  the  carcases,  clothed  with  their  flesh  and  skin,  had 
been  floated  down  soon  after  death,  and  while  they  were  still  swollen 
by  the  gases  generated  by  their  first  decomposition.  The  few  ac- 
companying shells  are  of  those  light  kinds  which  frequently  float  on 
the  surface  of  rivers,  together  with  wood. 

M.  Prevost  has  therefore  suggested  that  a  river  may  have  swept 
away  the  bodies  of  animals,  and  the  plants  which  lived  on  its  borders, 
or  in  the  lakes  which  it  traversed,  and  may  have  carried  them  down 
into  the  centre  of  the  gulf  into  which  flowed  the  waters  impregnated 
with  sulphate  of  lime.  We  know  that  the  Fiume  Salso  in  Sicily 
enters  the  sea  so  charged  with  various  salts  that  the  thirsty  cattle 
refuse  to  drink  of  it.  A  stream  of  sulphureous  water,  as  white  as 
milk,  descends  into  the  sea  from  the  volcanic  mountain  of  Idienne, 
on  the  east  of  Java ;  and  a  great  body  of  hot  water,  charged  with 
sulphuric  acid,  rushed  down  from  the  same  volcano  on  one  occasion, 
and  inundated  a  large  tract  of  country,  destroying,  by  its  noxious 


CH.  XVI.]  GYPSEOUS   SERIES.  225 

properties,  all  the  vegetation.*  In  like  manner  the  Pusanibio,  or 
"  Vinegar  River,"  of  Colombia,  which  rises  at  the  foot  of  Purace,  an 
extinct  volcano,  7,500  feet  above  the  level  of  the  sea,  is  strongly  impreg- 
nated with  sulphuric  and  hydrochloric  acids  and  with  oxide  of  iron. 
We  may  easily  suppose  the  waters  of  such  streams  to  have  properties 
noxious  to  marine  animals,  and  in  this  manner  the  entire  absence  of 
marine  remains  in  the  ossiferous  gypsum  may  be  explained.f  There 
are  no  pebbles  or  coarse  sand  in  the  gypsum ;  a  circumstance  which 
agrees  well  with  the  hypothesis  that  these  beds  were  precipitated 
from  water  holding  sulphate  of  lime  in  solution,  and  floating  the 
remains  of  different  animals. 

In  this  formation  the  relics  of  about  fifty  species  of  quadrupeds, 
including  the  genera  Paleotherium  (see  fig.  191.),  Anoplotherium 
(see  fig.  190.),  and  others,  have  been  found,  all  extinct,  and  nearly 
four-fifths  of  them  belonging  to  a  division  of  the  order  Pachydermata, 
which  is  now  represented  by  only  four  living  species ;  namely,  three 
tapirs  and  the  daman  of  the  Cape.  With  them  a  few  carnivorous 
animals  are  associated,  among  which  are  the  Hycenodon  dasyuroides, 
and  a  species  of  dog,  Canis  Parisiensis,  and  a  weasel,  Cynodon 
Parisiensis.  Of  the  Rodentia,  are  found  a  squirrel;  of  the  In- 
sectivora,  a  bat ;  while  the  Marsupialia  (an  order  now  confined  to 
America,  Australia,  and  some  contiguous  islands)  are  represented  by 
an  opossum. 

Of  birds,  about  ten  species  have  been  ascertained,  the  skeletons  of 
some  of  which  are  entire.  None  of  them  are  referable  to  existing 
species.J  The  same  remark  applies  to  the  fish,  according  to  MM. 
Cuvier  and  Agassiz,  as  also  to  the  reptiles.  Among  the  last  are 
crocodiles  and  tortoises  of  the  genera  Emys  and^  Trionyx. 

The  tribe  of  land  quadrupeds  most  abundant  in  this  formation  is 
such  as  now  inhabits  alluvial  plains  and  marshes,  and  the  banks  of 
rivers  and  lakes,  a  class  most  exposed  to  suffer  by  river  inundations. 
Among  these  were  several  species  of  Paleofhere,  a  genus,  before 
alluded  to  (p.  211.).  These  were  associated  with  the  Anoplotherium^ 
a  tribe  intermediate  between  pachyderms  and  ruminants.  One  of  the 
three  divisions  of  this  family  was  called  by  Cuvier  Xiphodon  (see 
fig.  235.).  Their  forms  were  slender  and  elegant,  and  one,  named 
Xiphodon  gracile  (fig.  235.),  was  about  the  size  of  the  chamois ;  and 
Cuvier  inferred  from  the  skeleton  that  it  was  as  light,  graceful, 
and  agile  as  the  gazelle. 

When  the  French  osteologist  declared,  in  the  early  part  of  the 
present  century,  that  all  the  fossil  quadrupeds  of  the  gypsum  of 
Paris  were  extinct,  the  announcement  of  so  startling  a  fact,  on  such 
high  authority,  created  a  powerful  sensation,  and  from  that  time  a 
new  impulse  was  given  throughout  Europe  to  the  progress  of 
geological  investigation.  Eminent  naturalists,  it  is  true,  had  long 

*  Leyde  Magaz.  voor  Wetensch  Konst  f  M.  C.  Prevost,  Submersions  Itera- 

en  Lett.,  partie  v.  cahier  i.  p.  7 1 .     Cited  tives,  &c.     Note  23. 

by  Rozet,  Journ.   de  Geologic,  torn.  i.  \  Cuvier,  Oss.  Foss.,  torn.  iii.  p.  255. 
p.  43. 


226 


CALCAIRE    SILICEUX. 


TCn.  XVL 


before  maintained  that  the  shells  and  zoophytes,  met  with  in  many 
ancient  European  rocks,  had  ceased  to  be  inhabitants  of  the  earth. 


Fig.  235. 


Xiphodon  gracile,  or  Anoplotherium  gracile,  Cuvier.    Restored  outline. 

but  the  majority  even  of  the  educated  classes  continued  to  believe 
that  the  species  of  animals  and  plants  now  contemporary  with  man, 
were  the  same  as  those  which  had  been  called  into  being  when  the 
planet  itself  was  created.  It  was  easy  to  throw  discredit  upon  the  new 
doctrine  by  asking  whether  corals,  shells,  and  other  creatures  pre- 
viously unknown,  were  not  annually  discovered  ?  and  whether  living 
forms  corresponding  with  the  fossils  might  not  yet  be  dredged  up 
from  seas  hitherto  unexamined  ?  But  from  the  era  of  the  publica- 
tion of  Cuvier's  Ossements  Fossiles,  and  still  more  his  popular  Trea- 
tise called  "  A  Theory  of  the  Earth,"  sounder  views  began  to  prevail. 
It  was  clearly  demonstrated  that  most  of  the  mammalia  found  in  the 
gypsum  of  Montmartre  differed  even  generically  from  any  now  known 
to  exist,  and  the  extreme  improbability  that  any  of  them,  especially 
the  larger  ones,  would  ever  be  found  surviving  in  continents  yet  un- 
explored, was  made  manifest.  Moreover,  the  non-admixture  of  a 
single  living  species  in  the  midst  of  so  rich  a  fossil  fauna  was  a 
striking  proof  that  there  had  existed  a  state  of  the  earth's  surface 
zoologically  unconnected  with  the  present  state  of  things. 

Calcaire  siliceux,  or  Travertin  inferieur,  B.  2.  —  This  compact 
siliceous  limestone  extends  over  a  wide  area.  It  resembles  a  preci- 
pitate from  the  waters  of  mineral  springs,  and  is  often  traversed  by 
small  empty  sinuous  cavities.  It  is,  for  the  most  part,  devoid  of 
organic  remains,  but  in  some  places  contains  freshwater  and  land 
species,  and  never  any  marine  fossils.  The  siliceous  limestone  and 
the  calcaire  grossier  usually  occupy  distinct  parts  of  the  Paris  basin, 
the  one  attaining  its  fullest  development  in  those  places  where  the 
other  is  of  slight  thickness.  They  are  described  by  some  writers  as 
alternating  with  each  other  towards  the  centre  of  the  basin,  as  at 
Sergy  and  Osny ;  and  M,  Prevost  concludes,  that  while  to  the  north, 


CH.  XVI.]  CALCAIRE  GROSSIEJR.  227 

where  the  bay  was  probably  open  to  the  sea,  a  marine  limestone  was 
formed,  another  deposit  of  freshwater  origin  was  introduced  to  the 
southward,  or  at  the  head  of  the  bay.  It  is  supposed  that  during 
the  Eocene  period,  as  now,  the  ocean  was  to  the  north,  and  the  con- 
tinent, where  the  great  lakes  existed,  to  the  south.  From  that 
southern  region  we  may  suppose  a  body  of  freshwater  to  have  de- 
scended, charged  with  carbonate  of  lime  and  silica,  the  water  being 
perhaps  in  sufficient  volume  to  freshen  the  upper  end  of  the  bay. 

The  gypsum,  with  its  associated  marl  and  limestone,  is,  as  before 
stated,  in  greatest  force  towards  the  centre  of  the  basin,  where  the 
calcaire  grossier  and  calcaire  siliceux  are  less  fully  developed.  Hence 
M.  Prevost  infers,  that  while  those  two  principal  deposits  were 
gradually  in  progress,  the  one  towards  the  north,  and  the  other 
towards  the  south,  a  river  descending  from  the  east  may  have  brought 
down  the  gypseous  and  marly  sediment. 

Ores  de  Beauchamp  or  Sables  moyens,  B.  3.  — In  some  parts  of 
the  Paris  basin,  sands  and  marls,  called  the  Gres  de  Beauchamp,  or 
Sables  moyens,  divide  the  gypseous  beds  from  the  calcaire  grossier 
proper.  These  sands,  in  which  a  small  nummulite  (N.  variolaria) 
is  very  abundant,  contain  more  than  300  species  of  marine  shells, 
many  of  them  peculiar,  but  others  common  to  the  next  division. 

Calcaire  grossier,  upper  and  middle,  B.  4.  —  The  upper  division  of 
this  group  consists  in  great  part  of  beds  of  compact,  fragile  limestone, 
with  some  intercalated  green  marls.  The  shells  in  some  parts  are  a 
mixture  of  Cerithium,  Cyclostoma,  and  Corbula;  in  others  Limneus, 
Cerithium,  Paludina,  &c.  In  the  latter,  the  bones  of  reptiles  and 
mammalia,  Paleotherium  and  Lophiodon,  have  been  found.  The 
middle  division,  or  calcaire  grossier  proper,  consists  of  a  coarse  lime- 
stone, often  passing  into  sand.  It  contains  the  greater  number  of 
the  fossil  shells  which  characterize  the  Paris  basin.  No  less  than 
400  distinct  species  have  been  procured  from  a  single  spot  near 
Grignon,  where  they  are  embedded  in  a  calcareous  sand,  chiefly 
formed  of  comminuted  shells,  in  which,  nevertheless,  individuals  in 
a  perfect  state  of  preservation,  both  of  marine,  terrestrial,  and  fresh- 
water species,  are  mingled  together.  Some  of  the  marine  shells 
may  have  lived  on  the  spot ;  but  the  Cyclostoma  and  Limneus  must 
have  been  brought  thither  by  rivers  and  currents,  and  the  quantity  of 
triturated  shells  implies  considerable  movement  in  the  waters. 

Nothing  is  more  striking  in  this  assemblage  of  fossil  testacea  than 
the  great  proportion  of  species  referable  to  the  genus  Cerithium 
(see  p.  30.  fig.  44.).  There  occur  no  less  than  137  species  of  this 
genus  in  the  Paris  basin,  and  almost  all  of  them  in  the  calcaire 
grossier.  Most  of  the  living  Cyrithia  inhabit  the  sea  near  the  mouths 
of  rivers,  where  the  waters  are  brackish ;  so  that  their  abundance  in 
the  marine  strata  now  under  consideration  is  in  harmony  with  the 
hypothesis,  that  the  Paris  basin  formed  a  gulf  into  which  several 
rivers  flowed,  the  sediment  of  some  of  which  gave  rise  to  the  bods  of 
clay  and  lignite  before  mentioned ;  while  a  distinct  freshwater 

Q  2 


228 


EOCENE   FORAMINIFEKA. 


[Cn.  XVI. 


limestone,  called  calcaire  siliceux,  already  described,  was  precipitated 
from  the  waters  of  others  situated  farther  to  the  south. 

In  some  parts  of  the  calcaire  grossier  round  Paris,  certain  beds 
occur  of  a  stone  used  in  building,  and  called  by  the  French  geologists 
"  Miliolite  limestone."  It  is  almost  entirely  made  up  of  millions  of 
microscopic  shells,  of  the  size  of  minute  grains  of  sand,  which  all 
belong  to  the  class  Foraminifera.  Figures  of  some  of  these  are  given 
in  the  annexed  woodcut.  As  this  miliolitic  stone  never  occurs  in  the 


EOCENE  FORAMINIFERA. 


Fig. 


Fig.  237. . 


Calcarina  rarispina,  Desh. 
b.  natural  size,    a,  c.  same  magnified. 


Spirolina  stenostoma,  Desh. 
B.  natural  size.    A,  C,  D.  same  magnified. 


Triloculina  inflata,  Desh. 
6.  natural  size.        a,  c,  d.  same  magnified. 


Fig.  239. 


Clnvulina  corrugata,  Desh. 
a.  natural  size.  b,  c.  same  magnified. 

Faluns,  or  Miocene  strata  of  Brittany  and  Touraine,  it  often  fur- 
nishes the  geologist  with  a  useful  criterion  for  distinguishing  the 
detached  Eocene  and  Miocene  formations,  scattered  over  those  and 
other  adjoining  provinces.  The  discovery  of  the  remains  of  Paleo- 
therium  and  other  mammalia  in  some  of  the  upper  beds  of  the  cal- 
caire grossier  shows  that  these  land  animals  began  to  exist  before  the 
deposition  of  the  overlying  gypseous  series  had  commenced. 


CH.  XVI.] 


LITS   COQUILLIERS. 


229 


Lower  Calcaire  grassier,  or  Glauconie  grossier  e,  B.  5.  —  The  lower 
part  of  the  calcaire  grossier,  which  often  contains  much  green  earth, 
is  characterized  at  Auvers,  near  Pontoise,  to  the  north  of  Paris,  and 
still  more  in  the  environs  of  Compiegne,  by  the  abundance  of  nummu- 
lites,  consisting  chiefly  of  N.  Icevigata,  N.  scabra,  and  JV.  Lamarcki, 
which  constitute  a. large  proportion  of  some  of  the  stony  strata, 
though  these  same  foraminifera  are  wanting  in  beds  of  similar  age  in 
the  immediate  environs  of  Paris. 

Soissonnais  Sands  or  Lits  coquilliers,  B.  6.  —  Below  the  pre- 
ceding formation,  shelly  sands  are  seen,  of  considerable  thickness, 
especially  at  Cuisse-Lamotte,  near  Compiegne,  and  other  localities  in 
the  Soissonnais,  about  fifty  miles  N.E.  of  Paris,  from  which  about  300 
species  of  shells  have  been  obtained,  many  of  them  common  to  the 
Calcaire  grossier  and  the  Bracklesham  beds  of  England,  and  many  pe- 
culiar. The  Nummulites planulata  is  very  abundant,  and  the  most  cha- 
racteristic shell  is  the  Nerita  conoidea,  Lam.,  a  fossil  which  has  a 

Fig.  240. 


Nerita  conoiden,  Lam. 
Syn.  N.  Schemidelliana,  Chemnitz. 

very  wide  geographical  range ;  for,  as  M.  D' Archiac  remarks,  it  accom- 
panies the  nummulitic  formation  from  Europe  to  India,  having  been 
found  in  Cutch,  near  the  mouths  of  the  Indus,  associated  with  Num- 
mulites scabra.  No  less  than  thirty-three  shells  of  this  group  are 
said  to  be  identical  with  shells  of  the  London  clay  proper,  yet,  after 
visiting  Cuisse-Lamotte  and  other  localities  of  the  "  Sables  in- 
ferieures  "  of  Archiac,  I  agree  with  Mr.  Prestwich,  that  the  latter  are 
probably  newer  than  the  London  clay,  and  perhaps  older  than  the 
Bracklesham  beds  of  England.  The  London  clay  seems  to  be  unre- 
presented in  France,  unless  partially  so,  by  these  sands.*  One  of 
the  shells  of  the  sandy  beds  of  the  Soissonnais  is  adduced  by 
M.  Deshayes  as  an  example  of  the  changes  which  certain  species 

Fig.  241. 


Cardium  porulosum.    Paris  and  London  basins. 

*  D'  Archiac,  Bulletin,  torn,  x.;  and  Prestwich,  Geol.  Quart.  Journ.  1847,  p.  377. 

Q  3 


230  NUMMULITIC    FORMATIONS  [Cn.  XVI. 

underwent  in  the  successive  stages  of  their  existence.  It  seems  that 
different  varieties  of  the  Cardium  porulosum  are  characteristic  of 
different  formations.  In  the  Sossonnais  this  shell  acquires  but  a 
small  volume,  and  has  many  peculiarities,  which  disappear  in  the 
lowest  beds  of  the  calcaire  grossier.  In  these  the  shell  attains  its 
full  size,  with  many  distinctive  characters,  which,  are  again  modified 
in  the  uppermost  beds  of  the  calcaire  grossier ;  and  these  last  modi- 
fications of  form  are  preserved  throughout  the  "upper  marine" 
(or  Upper  Eocene)  series.* 

Argile  plastique  (C.  Table,  p.  223.).  — At  the  base  of  the  tertiary 
system  in  France  are  extensive  deposits  of  sands,  with  occasional 
beds  of  clay  used  for  pottery,  and  called  "  argile  plastique."  Fossil 
oysters  (Ostrea  bellovacind)  abound  in  some  places,  and  in  others 
there  is  a  mixture  of  fluviatile  shells,  such  as  Cyrena  cuneiformis  (fig. 
233.  p.  321.),  Melania  inquinata  (fig.  234.),  and  others,  frequently  met 
with  in  beds  occupying  the  same  position  in  the  valley  of  the  Thames. 
Layers  of  lignite  also  accompany  the  inferior  clays  and  sands. 

Immediately  upon  the  chalk  at  the  bottom  of  all  the  tertiary  strata 
in  France  there  generally  is  a  conglomerate  or  breccia  of  rolled  and 
angular  chalk-flints,  cemented  by  siliceous  sand.  These  beds  appear 
to  be  of  littoral  origin,  and  imply  the  previous  emergence  of  the  chalk, 
and  its  waste  by  denudation. 

Whether  the  Thanet  sands  before  mentioned  (p.  222.)  are  exactly 
represented  in  the  Paris  basin  is  still  a  matter  of  discussion. 

Wide  extent  of  the  nummulitic  formation  in  Europe,  Asia,  fyc. — 
When  I  visited  Belgium  and  French  Flanders  in  1851,  with  a  view 
of  comparing  the  tertiary  strata  of  those  countries  with  the  English 
series,  I  found  that  all  the  beds  between  the  Upper  Eocene  or  Limburg 
formations,  and  the  Lower  Eocene  or  London  clay  proper,  might  be 
conveniently  divided  into  three  sections,  distinguished,  among  other 
paleontological  characters,  by  three  different  species  of  nummulites, 
N.  variolaria  in  the  upper  beds,  N.  Iwvigata  in  the  middle,  and  N. 
planulata  in  the  lower.  After  I  had  adopted  this  classification,  I 
found,  what  I  had  overlooked  or  forgotten,  that  the  superposition  of 
these  three  species  in  the  order  here  assigned  to  them,  had  been 
previously  recognized  in  the  North  of  France,  in  1842,  by  Viscount 
D'Archiac.  The  same  author,  in  the  valuable  monograph  recently 
published  by  himt,  has  observed,  that  a  somewhat  similar  distribu- 
tion of  these  and  other  species  in  time,  prevails  very  widely  in  the 
South  of  France  and  in  the  Pyrenees,  as  well  as  in  the  Alps  and 
Apennines,  and  in  Istria, — the  lowest  nummulitic  beds  being  charac- 
terized by  fewer  and  smaller  species,  the  middle  by  a  greater  number 
and  by  those  which  individually  attain  the  largest  dimensions,  and 
the  uppermost  beds  again  by  small  species. 

In  the  treatise  alluded  to,  M.  D'Archiac  describes  no  less  than  fifty- 
two  species  of  this  genus,  and  considers  that  they  are  all  of  them  cha- 

*  Coquilles  caracteristiques  des  ter-  f  Animaux  foss.  du  groupe  nummuL 
rains,  1831.  de  1'Inde  :  Paris,  1853. 


CH.  XVL]  IN   EUROPE   AND   ASIA.  231 

racteristic  of  those  tertiary  strata  which  I  have  called  Middle  Eocene. 
In  very  few  instances  at  least  do  certain  species  diverge  from 
this  narrow  limit,  whether  into  incumbent  or  subjacent  tertiary 
formations,  it  being  rather  doubtful  whether  more  than  one  of 
them,  Nummulites  intermedia,  also  a  Middle  Eocene  fossil,  ascends 
so  high  as  the  Miocene  formation,  or  whether  any  of  them  descend 
to  the  level  of  the  London  clay.  Certainly  they  have  never  been 
traced  so  low  down  as  the  marine  beds,  coeval  with  the  Plastic 
clay  or  Lignite,  in  any  country  of  which  the  geology  has  been  well 
worked  out.  This  conclusion  is  a  very  unexpected  result  of  recent 
inquiry,  since  for  many  years  it  was  a  matter  of  controversy  whether 
the  nummulitic  rocks  of  the  Alps  and  Pyrenees  ought  not  to  be  re- 
garded as  cretaceous  rather  than  Eocene.  The  late  M.  Alex. 
Brongniart  first  declared  the  specific  identity  of  many  shells  of  the 
marine  strata  near  Paris,  and  those  of  the  nummulitic  formation  of 
Switzerland,  although  he  obtained  these  last  from  the  summit  of  the 
Diablerets,  one  of  the  loftiest  of  the  Swiss  Alps,  which  rises  more 
than  10,000  feet  above  the  level  of  the  sea. 

The  nummulitic  limestone  of  the  Alps  is  often  of  great  thickness, 
and  is  immediately  covered  by  another  series  of  strata  of  dark- 
coloured  slates,  marls,  and  fucoidal  sandstones,  to  the  whole  of  which 
the  provincial  name  of  "  flyseh  "  has  been  given  in  parts  of  Switzer- 
land. The  researches  of  Sir  Roderick  Murchison  in  the  Alps  in 
1847  have  shown  that  all  these  tertiary  strata  enter  into  the  disturbed 
and  loftiest  portions  of  the  Alpine  chain,  to  the  upheaval  of  which 
they  enable  us  therefore  to  assign  a  comparatively  modern  date. 

The  nummulitic  formation,  with  its  characteristic  fossils,  plays  a 
far  more  conspicuous  part  than  any  other  tertiary  group  in  the  solid 
framework  of  the  earth's  crust,  whether  in  Europe,  Asia,  or  Africa. 
It  often  attains  a  thickness  of  many  thousand  feet,  and  extends  from 
the  Alps  to  the  Carpathians,  and  is  in  full  force  in  the  north  of  Africa, 
as,  for  example,  in  Algeria  and  Morocco.  It  has  also  been  traced 
from  Egypt,  where  it  was  largely  quarried  of  old  for  the  building  of 
the  Pyramids,  into  Asia  Minor,  and  across  Persia  by  Bagdad  to  the 
mouths  of  the  Indus.  It  occurs  not  only  in  Cutch,  but  in  the  mountain 
ranges  which  separate  Scinde  from  Persia,  and  which  form  the  passes 
leading  to  Caboul ;  and  it  has  been  followed  still  farther  eastward  into 
India,  as  far  as  eastern  Bengal  and  the  frontiers  of  China. 

Fig.  242. 


Nummulites  Puschi,  D'Archiac.     Peyrehorade,  Pyrenees. 
a.  external  surface  of  one  of  the  nummulites,  of  which  longitudinal  sections  are  seen  in  the 

limestone. 
b.  transverse  section  of  same. 

Q  4 


232  EOCENE    STRATA  [Cn.  XVI. 

Dr.  T.  Thomson  found  nummulites  at  an  elevation  of  no  less  than 
16,500  feet  above  the  level  of  the  sea,  in  Western  Thibet. 

One  of  the  species,  which  I  myself  found  very  abundant  on  the  flanks 
Fig.  2i3.  of  the  Pyrenees,  in  a  compact  crystalline  marble 

(fig.  242.)  is  called  by  M.  D'Archiac  Nummulites 
Puschi.  The  same  is  also  very  common  in  rocks 
of  the  same  age  in  the  Carpathians. 

Another  large  species  (see  fig.  243.),  Nummulites 
exponens,  J.  Sow.,  occurs  not  only  in  the  South 
of  France,  near  Dax,  but  in  Germany,  Italy,  Asia 
Minor,  and  in  Cutch;  also  in  the  mountains  of 

Nummulites  exponent,      £,    •.,      '  ,•.        /»         ,•  e*  /~ii_  • 

Sow.   Europe  and  India.  Sylhet,  on  the  frontiers  oi  China. 

In  many  of  the  distant  countries  above  alluded  to,  in  Cutch,  for 
example,  some  of  the  same  shells,  such  as,  Nerita  conoidea  (fig. 
240.),  accompany  the  Nummulites  as  in  France. 

The  opinion  of  many  observers,  that  the  nummulitic  formation 
belongs  partly  to  the  cretaceous  era,  seems  chiefly  to  have  arisen 
from  confounding  an  allied  genus,  Orbitoides,  with  the  true  Num- 
mulite. 

When  we  have  once  arrived  at  the  conviction  that  the  nummulitic 
formation  occupies  a  middle  place  in  the  Eocene  series,  we  are  struck 
with  the  comparatively  modern  date  to  which  some  of  the  greatest 
revolutions  in  the  physical  geography  of  Europe,  Asia,  and  Northern 
Africa  must  be  referred.  All  the  mountain  chains,  such  as  the  Alps, 
Pyrenees,  Carpathians,  and  Himalayas,  into  the  composition  of  whose 
central  and  loftiest  parts  the  nummulitic  strata  enter  bodily,  could 
have  had  no  existence  till  after  the  Middle  Eocene  period.  During 
that  period  the  sea  prevailed  where  these  chains  now  rise,  for  num- 
mulites and  their  accompanying  testacea  were  unquestionably  inhabi- 
tants of  salt  water.  Before  these  events,  comprising  the  conversion 
of  a  wide  area  from  a  sea  to  a  continent,  England  had  been  peopled, 
as  I  before  pointed  out  (p.  220.),  by  various  quadrupeds,  by  herbi- 
vorous pachyderms,  by  insectivorous  bats,  by  opossums  and  monkeys. 

Almost  all  the  extinct  volcanoes  which  preserve  any  remains  of 
their  original  form,  or  from  the  craters  of  which  lava  streams  can  be 
traced,  are  more  modern  than  the  Eocene  fauna  now  under  consi- 
deration ;  and  besides  these  superficial  monuments  of  the  action  of  heat, 
Plutonic  influences  have  worked  vast  changes  in  the  texture  of  rocks 
within  the  same  period.  Some  members  of  the  nummulitic  and 
overlying  tertiary  strata  called  flysch  have  actually  been  converted 
in  the  Central  Alps  into  crystalline  rocks,  and  transformed  into 
marble,  quartz-rock,  mica-schist,  and  gneiss.* 

EOCENE    STRATA   IN   THE   UNITED   STATES. 

In  North  America  the  Eocene  formations  occupy  a  large  area 
bordering  the  Atlantic,  which  increases  in  breadth  and  importance  as 
it  is  traced  southwards  from  Delaware  and  Maryland  to  Georgia  and 

*  Murchison,  Quart.  Journ.  of  Geol.  Soc.  vol.  v.,  and  Lrell,  vol.  vi.  1850. 
Anniversary  Address. 


CH.  XVI.]  IN   THE   UNITED    STATES.  233 

Alabama.  They  also  occur  in  Louisiana  and  other  states  both  east 
and  west  of  the  valley  of  the  Mississippi.  At  Claiborne  in  Alabama 
no  less  than  four  hundred  species  of  marine  shells,  with  many  echi- 
noderms  and  teeth  of  fish,  characterize  one  member  of  this  system. 
Among  the  shells,  the  Cardita  planicosta,  before  mentioned  (fig.  216. 
p.  215.),  is  in  abundance ;  and  this  fossil,  and  some  others  identical 
with  European  species,  or  very  nearly  allied  to  them,  make  it  highly 
probable  that  the  Claiborne  beds  agree  in  age  with  the  central  or 
Bracklesham  group  of  England,  and  with  the  calcaire  grossier  of 
Paris.* 

Higher  in  the  series  is  a  remarkable  calcareous  rock,  formerly  called 
"  the  nummulite  limestone,"  from  the  great  number  of  discoid  bodies 
resembling  numnmlites  which  it  contains,  fossils  now  referred  by 
A.  d'Orbigny  to  the  genus  Orbitoides,  which  has  been  demonstrated 
by  Dr.  Carpenter  to  belong  to  the  foraminifera.|  That  naturalist 
moreover  is  of  opinion  that  the  Orbitoides  alluded  to  (0.  Mantelli) 
is  of  the  same  species  as  one  found  in  Cutch  in  the  Middle  Eocene  or 
nummulitic  formation  of  India.  The  following  section  will  enable 
the  reader  to  understand  the  position  of  three  subdivisions  of  the 
Eocene  series,  Nos.  1 ,  2,  and  3,  the  relations  of  which  I  ascertained 
in  Clarke  County,  between  the  rivers  Alabama  and  Tombeckbee. 


1.  Sand,  marl,  &c.,  with  numerous  fossils.  ) 

2.  White  or  rotten  limestone,  with  Zeuglodon.        >  Eocene. 

3.  Orbitoidal,  or  so  called  nummulitie  limestone.   ) 

4.  Overlying  formation  of  sand  and  clay  without  fossils.    Age  unknown. 

The  lowest  set  of  strata,  No.  1,  having  a  thickness  of  more  than 
100  feet,  comprise  marly  beds,  in  which  the  Ostrea  sellceformis  occurs, 
a  shell  ranging  from  Alabama  to  Virginia,  and  being  a  representa- 
tive form  of  the  Ostrea  flabellula  of  the  Eocene  group  of  Europe. 
In  other  beds  of  No.  1,  two  European  shells,  Cardita  planicosta, 
before  mentioned,  and  Solarium  canaliculatum,  are  found,  with  a 
great  many  other  species  peculiar  to  America.  Numerous  corals, 
also,  and  the  remains  of  placoid  fish  and  of  rays,  occur,  and  the 
"  swords,"  as  they  are  callwd,  of  sword  fishes,  all  bearing  a  great 
generic  likeness  to  those  of  the  Eocene  strata  of  England  and  France. 

No.  2  (fig.  244.)  is  a  white  limestone,  sometimes  soft  and  argilla- 


*  See  paper  by  the  author,   Quart.        f  Quart.  Journ.    GeoL   Soc.  voL  vi. 
Journ.  Geol.    Soc.   vol.  iv.  p.  12.;  and     p.  32. 
Second  Visit  to  the  U.  S.  vol.  ii.  p.  59. 


234  EOCENE    STRATA   IN   UNITED    STATES.  [Ce.  XVI. 

ceous,  but  in  parts  very  compact  and  calcareous.  It  contains  several 
peculiar  corals,  and  a  large  Nautilus  allied  to  N.  ziczac ;  also  in  its 
upper  bed  a  gigantic  cetacean,  called  Zeuglodon  by  Owen.* 

Fig.  245.  Fig.  246. 


Zeuglodon  cetoirfcs,  Owen. 
Sasilosaurus,  Harlan. 
Fig.  245.  Molar  tooth,  natural  size.  Fig.  246.  Vertebra,  reduced. 

The  colossal  bones  of  this  cetacean  are  so  plentiful  in  the  interior 
of  Clarke  County  as  to  be  characteristic  of  the  formation.  The  ver- 
tebral column  of  one  skeleton  found  by  Dr.  Buckley  at  a  spot  visited 
by  me,  extended  to  the  length  of  nearly  70  feet,  and  not  far  off  part 
of  another  backbone  nearly  50  feet  long  was  dug  up.  I  obtained 
evidence,  during  a  short  excursion,  of  so  many  localities  of  this  fossil 
animal  within  a  distance  of  10  miles,  as  to  lead  me  to  conclude  that 
they  must  have  belonged  to  at  least  forty  distinct  individuals. 

Prof.  Owen  first  pointed  out  that  this  huge  animal  was  not  reptilian, 
since  each  tooth  was  furnished  with  double  roots  (see  fig.  245.), 
implanted  in  corresponding  double  sockets ;  and  his  opinion  of  the 
cetacean  nature  of  the  fossil  was  afterwards  confirmed  by  Dr.  Wyman 
and  Dr.  R.  W.  Gibbes.  That  it  was  an  extinct  mammal  of  the 
whale  tribe  has  since  been  placed  beyond  all  doubt  by  the  discovery 
of  the  entire  skull  of  another  fossil  species  of  the  same  family,  having 
the  double  occipital  condyles  only  met  with  in  mammals,  and  the 
convoluted  tympanic  bones  which  are  characteristic  of  cetaceans. 

Near  the  junction  of  No.  2  and  the  incumbent  limestone,  No.  3, 
next  to  be  mentioned,  are  strata  characterized  by  the  following  shells  : 
Spondylus  dumosus  (Plagiostoma  dumosum,  Morton),  Pecten  Poul- 
soni,  Pecten  perplanus,  and  Ostrea  cretacea. 

No.  3  (fig.  244.)  is  a  white  limestone,  for  the  most  part  made  up  of  the 
Orbitoides  of  D'Orbigny  before  mentioned  (p.  233.),  formerly  supposed 
to  be  a  nummulite,  and  called  .2V".  Mantelli.,  mixed  with  a  few  lunulites 
some  small  corals  and  shells. f  The  origin,  therefore,  of  this  cream- 
coloured  soft  stone,  like  that  of  our  white  chalk,  which  it  much  re- 
sembles, is,  I  believe,  due  to  the  decomposition  of  these  foraminifera. 
The  surface  of  the  country  where  it  prevails  is  sometimes  marked  by 

*  See    Memoir    by    K.  W.    Gibbes,         |  I>yell,    Quart.    Journ.    Geol.   Soc. 
Journ.  of  Acad.  Nat.  Sci.  Philad.  vol.  i.     1847,  vol.  iv.  p.  15. 
1847. 


Cm  XVII.]  CRETACEOUS   GROUPS.  235 

the  absence  of  wood,  like  our  chalk  downs,  or  is  covered  exclusively 
by  the  Juniperus  Virginiana,  as  certain  chalk  districts  in  England 
by  the  yew  tree  and  juniper. 

Some  of  the  shells  of  this  limestone  are  common  to  the  Claiborne 
beds,  but  many  of  them  are  peculiar. 

It  will  be  seen  in  the  section  (fig.  244.  p.  233.)  that  the  strata 
Nos.  1,  2,  3  are,  for  the  most  part,  overlaid  by  a  dense  formation  of 
sand  or  clay  without  fossils.  In  some  points  of  the  bluff  or  cliff  of 
the  Alabama  river,  at  Claiborne,  the  beds  Nos.  1,  2  are  exposed 
nearly  from  top  to  bottom,  whereas  at  other  points  the  newer  form- 
ation, No.  4,  occupies  the  face  of  nearly  the  whole  cliff.  The  age  of 
this  overlying  mass  has  not  yet  been  determined,  as  it  has  hitherto 
proved  destitute  of  organic  remains. 

The  burr-stone  strata  of  the  Southern  States  contain  so  many 
fossils  agreeing  with  those  of  Claiborne,  that  it  doubtless  belongs  to 
the  same  part  of  the  Eocene  group,  though  I  was  not  fortunate  enough 
to  see  the  relations  of  the  two  deposits  in  a  continuous  section. 
Mr.  Tuomey  considers  it  as  the  lower  portion  of  the  series.  It  may, 
perhaps,  be  a  form  of  the  Claiborne  beds  in  places  where  lime  was 
wanting,  and  where  silex,  derived  from  the  decomposition  of  felspar, 
predominated.  It  consists  chiefly  of  slaty  clays,  quartzose  sands,  and 
loam,  of  a  brick  red  colour,  with  layers  of  chert  or  burr-stone,  used  in 
some  places  for  mill-stones. 


CHAPTER  XVII.   i 

CRETACEOUS  GROUP. 

Lapse  of  time  between  the  Cretaceous  and  Eocene  periods — Whether  certain 
formations  in  Belgium  and  France  are  of  intermediate  age  — Pisolitic  limestone 
— Divisions  of  the  Cretaceous  series  in  North- Western  Europe — Maestricht 
beds  —  Chalk  of  Faxoe  —  White  chalk — Its  geographical  extent  and  origin — 
Formed  in  an  open  and  deep  sea — How  far  derived  from  shells  and  corals- 
Single  pebbles  in  chalk  — Chalk  flints, — Potstones  of  Horstead — Fossils  of 
the  Upper  Cretaceous  rocks — Echinoderms,  Mollusca,  Bryozoa,  Sponges — 
Upper  Greensand  and  Gault  —  Chalk  of  South  of  Europe — Hippurite  limestone 
—  Cretaceous  rocks  of  the  United  States. 

HAVING  treated  in  the  preceding  chapters  of  the  tertiary  strata,  we 
have  next  to  speak  of  the  uppermost  of  the  secondary  groups,  com- 
monly called  the  chalk,-  or  the  cretaceous  strata,  from  creta,  the 
Latin  name  for  that  remarkable  white  earthy  limestone,  which 
constitutes  an  upper  member  of  the  group  in  these  parts  of  Europe, 
where  it  was  first  studied.  The  marked  discordance  in  the  fossils 
of  the  tertiary,  as  compared  with  the  cretaceous  formations,  has  long 
induced  many  geologists  to  suspect  that  an  indefinite  series  of  ages 
elapsed  between  the  respective  periods  of  their  origin.  Measured, 
indeed,  by  such  a  standard,  that  is  to  say,  by  the  amount  of  change  in 


236  PISOLITIC   LIMESTONE    OF    FRANCE.  [Cn.  XVII. 

the  Fauna  and  Flora  of  the  earth  effected  in  the  interval,  the  time 
between  the  cretaceous  and  Eocene  may  have  been  as  great  as  that  be- 
tween the  Eocene  and  recent  periods,  to  the  history  of  which  the  last 
seven  chapters  have  been  devoted.  Several  fragmentary  deposits  have 
been  met  with  here  and  there,  in  the  course  of  the  last  half  century, 
of  an  age  intermediate  between  the  white  chalk  and  the  plastic  clays 
and  sands,  of  the  Paris  and  London  districts,  monuments  which  have 
the  same  kind  of  interest  to  a  geologist,  which  certain  mediaeval 
records  excite  when  we  study  the  history  of  nations.  For  both  of 
them  throw  light  on  ages  of  darkness,  preceded  and  followed  by 
others  of  which  the  annals  are  comparatively  well  known  to  us.  But 
these  newly  discovered  records  do  not  fill  up  the  wide  gap,  some  of 
them  being  closely  allied  to  the  Eocene,  and  others  to  the  cretaceous 
type,  while  none  appear  as  yet  to  possess  so  distinct  and  characteristic 
a  fauna,  as  may  entitle  them  to  hold  an  independent  place  in  the  great 
chronological  series. 

Among  the  formations  alluded  to,  the  Thanet  Sands  of  Prestwich 
have  been  sufficiently  described  in  the  last  chapter,  and  classed  as 
Lower  Eocene.  To  the  same  tertiary  series  belong  the  Belgian  form- 
ations, called  by  Professor  Dumont,  Landenian  and  Heersian,  although 
these  are  probably  of  higher  antiquity  than  the  Thanet  Sands.  On 
the  other  hand,  the  Maestricht  and  Faxoe  limestones  are  very  closely 
connected  with  the  chalk,  to  which  also  the  Pisolitic  limestone  of 
France  has  been  recently  referred  by  high  authorities. 

The  Lower  Landenian  beds  of  Belgium  consist  of  marls  and  sands, 
often  containing  much  green  earth,  called  glauconite.  They  may  be 
seen  at  Tournay,  and  at  Angres,  near  Mons,  and  at  Orp-le- Grand, 
Lincent,  and  Landen  in  the  ancient  province  of  Hesbaye,  in  Belgium, 
where  they  supply  a  durable  building-stone,  yet  one  so  light  as  to  be 
easily  transported.  Some  few  shells  of  the  genus  Pholodamya, 
Scalaria,  and  others,  agree  specifically  with  fossils  of  the  Thanet 
Sands ;  but  most  of  them,  such  as  Astarte  incequilatera,  Nyst,  are 
peculiar.  In  the  building-stone  of  Orp-le-Grand,  I  found  a  Cardiaster, 
a  genus  which,  according  to  Professor  E.  Forbes,  was  previously 
unknown  in  rocks  newer  than  the  cretaceous. 

Still  older  than  the  Lower  Landenian  is  the  marl,  or  calcareous 
glauconite  of  the  village  of  Heers,  near  Waremme,  in  Belgium ;  also 
seen  at  Marlinne  in  the  same  district,  where  I  have  examined  it.  It 
has  been  sometimes  classed  with  the  cretaceous  series,  although  as  yet 
it  has  yielded  no  forms  of  a  decidedly  cretaceous  aspect,  such  as 
Ammonite,  Baculite,  Belemnite,  Hippurite,  .&c.  The  species  of 
shells  are  for  the  most  part  new;  but  it  contains,  according  to 
M.  Hebert,  Pholodamya  cuneata,  an  Eocene  fossil,  and  he  assigns  it 
with  confidence  to  the  tertiary  series. 

Pisolitic  limestone  of  France.  —  Geologists  have  been  still  more  at 
variance  respecting  the  chronological  relations  of  this  rock,  which  is 
met  with  in  the  neighbourhood  of  Paris,  and  at  places  north,  south, 
east,  and  west  of  that  metropolis,  as  between  Vertus  and  Laversines, 
Meudon  and  Montereau.  It  is  usually  in  the  form  of  a  coarse 
yellowish  or  whitish  limestone,  and  the  total  thickness  of  the  series 


CH.  XVII.]      CLASSIFICATION   OF    CRETACEOUS   ROCKS.  237 

of  beds  already  known  is  about  100  feet.  Its  geographical  range, 
according  to  M.  Hebert,  is  not  less  than  45  leagues  from  east  to 
west,  and  35  from  north  to  south.  Within  these  limits  it  occurs  in 
small  patches  only,  resting  unconformably  on  the  white  chalk.  It 
was  originally  regarded  as  cretaceous  by  M.  E.  de  Beaumont,  on  the 
ground  of  its  having  undergone,  like  the  white  chalk,  extensive 
denudation  previous  to  the  Eocene  period ;  but  many  able  paleon- 
tologists, and  among  others  MM.  C.  D'Orbigny,  Deshayes,  and 
D'Archiac,  disputed  this  conclusion,  and,  after  enumerating  54  species 
of  fossils,  declared  that  their  appearance  was  more  tertiary  than 
cretaceous.  More  recently,  M.  Hebert  having  found  the  Pecten 
quadricostatus,  a  cretaceous  species,  in  this  same  pisolitic  rock,  at 
Montereau  near  Paris,  and  some  few  other  fossils  common  to  the 
Maestricht  chalk,  and  to  the  Baculite  limestone  of  the  Cotentin,  in 
Normandy,  classed  it  as  an  upper  member  of  the  cretaceous  group, 
an  opinion  since  adopted  by  M.  Alcide  D'Orbigny,  who  has  carefully 
examined  the  fossils.  The  Nautilus  Danicus,  fig.  249.,  and  two  or 
three  other  species  found  in  this  rock,  are  frequent  in  that  of  Faxoe 
in  Denmark,  but  as  yet  no  Ammonites,  Hamites,  Scaphites,  Turrilites, 
BaculiteSj  or  Hippurites  have  been  met  with.  The  proportion  of 
peculiar  species,  many  of  them  of  tertiary  aspect,  is  confessedly  large ; 
and  great  aqueous  erosion  suffered  by  the  white  chalk,  before  the 
pisolitic  limestone  was  formed,  affords  an  additional  indication  of  the 
two  deposits  being  widely  separated  in  time.  The  pisolitic  formation, 
therefore,  may  eventually  prove  to  be  somewhat  more  intermediate 
in  date  between  the  secondary  and  tertiary  epochs  than  the 
Maestricht  rock. 

It  should  however  be  observed,  that  all  the  above-mentioned  strata, 
from  the  Thanet  Sands  to  the  Pisolitic  limestone  inclusive,  and  even 
the  Maestricht  rock,  next  to  be  described,  exhibit  marks  of  denudation, 
experienced  at  various  dates,  subsequently  to  the  consolidation  of  the 
white  chalk.  This  fact  helps  us  in  some  degree  to  explain  the 
remarkable  break  in  the  sequence  of  European  rocks,  between  the 
secondary  and  tertiary  eras,  for  many  strata  which  once  existed  have 
doubtless  been  swept  away. 

CLASSIFICATION   OF   THE    CRETACEOUS   ROCKS. 

The  cretaceous  group  has  generally  been  divided  into  an  Upper  and 
a  Lower  series,  each  of  them  comprising  several  subdivisions,  dis- 
tinguished by  peculiar  fossils,  and  sometimes  retaining  a  uniform 
mineral  character  throughout  wide  areas.  The  Upper  series  is  often 
called  familiarly  the  chalk,  and  the  Lower  the  greensand,  the  last- 
mentioned  name  being  derived  from  the  green  colour  imparted  to 
certain  strata  by  grains  of  chloritic  matter.  The  following  table 
comprises  the  names  of  the  subdivisions  most  commonly  adopted :  — 

UPPER  CRETACEOUS. 

A.  1.  Maestricht  beds  and  Faxoe  limestones. 

2.  White  chalk  with  flints. 

3,  Chalk  marl,  or  grey  chalk  slightly  argillaceous. 


238  MAESTRICHT    BEDS.  [Cn.  XVII. 

4.  Upper  greensand,  occasionally  with  beds  of  chert,  and  with  chloritic  marl 

(craie  chloritee  of  French  authors)  in  the  upper  portion. 

5.  Gault,  including  the  Blackdown  beds. 

LOWER  CRETACEOUS  (or  Neocomian). 

B.  1.  Lower  greensand  —  Greensand,   Ironsand,    clay,   and  occasional   beds   of 

limestone  (Kentish  Eag). 
2.  Wealden  beds  or  Weald  clay  and  Hastings  sands.* 

Maastricht  Beds.  —  On  the  banks  of  the  Meuse,  at  Maestricht, 
reposing  on  ordinary  white  chalk  with  flints,  we  find  an  upper  cal- 
careous formation  about  100  feet  thick,  the  fossils  of  which  are,  on 
the  whole,  very  peculiar,  and  all  distinct  from  tertiary  species.  Some 
few  are  of  species  common  to  the  inferior  white  chalk,  among  which 
may  be  mentioned  Belemnites  mucronatus  (fig.  256.  p.  246.)  and 
Pecten  quadricostatus,,  a  shell  regarded  by  many  as  a  mere  variety  of 
P.  quinquecostatus  (see  fig.  271.)-  Besides  the  Belemnite  there  are 
other  genera^  such  as  Baculite  and  Hamite,  never  found  in  strata 
newer  than  the  cretaceous,  but  frequently  met  with  in  these  Maes- 
tricht beds.  On  the  other  hand,  Valuta,  Fasciolaria,  and  other 
genera  of  univalve  shells,  usually  met  with  only  in  tertiary  strata, 
occur. 

The  upper  part  of  the  rock,  about  20  feet  thick,  as  seen  in  St. 
Peter's  Mount,  in  the  suburbs  of  Maestricht,  abounds  in  corals  and 
Bryozoa,  often  detachable  from  the  matrix ;  and  these  beds  are 
succeeded  by  a  soft  yellowish  limestone  50  feet  thick,  extensively 
quarried  from  time  immemorial  for  building.  The  stone  below  is 
whiter,  and  contains  occasional  nodules  of  grey  chert  or  chalcedony. 

M.  Bosquet,  with  whom  I  examined  this  formation  (August,  1850), 
pointed  out  to  me  a  layer  of  chalk  from  2  to  4  inches  thick,  con- 
taining green  earth  and  numerous  encrinital  stems,  which  forms 
the  line  of  demarcation  between  the  strata  containing  the  fossils 
peculiar  to  Maestricht  and  the  white  chalk  below.  The  latter  is  dis- 
tinguished by  regular  layers  of  black  flint  in  nodules,  and  by  several 
shells,  such  as  Terebratula  carnea  (see  fig.  267.),  wholly  wanting 
in  beds  higher  than  the  green  band.  Some  of  the  organic  remains, 
however,  for  which  St.  Peter's  Mount  is  celebrated,  occur  both  above 
and  below  that  parting  layer,  and,  among  others,  the  great  marine 
reptile  called  Mosasaurus  (see  fig.  247.),  a  saurian  supposed  to  have 
been  24  feet  in  length,  of  which  the  entire  skull  and  a  great  part  of 

*  M.  Alcide  d'Orbigny,  in  his  valuable  work  entitled  Paleontologie  Fra^aise, 
has  adopted  new  terms  for  the  French  subdivisions  of  the  Cretaceous  Series,  which, 
so  far  as  they  can  be  made  to  tally  with  English  equivalents,  seem  explicable  thus: 

Danien.  Maestricht  beds. 

Senonien.  "White  chalk,  and  chalk  marl. 

Turonien.  Part  of  the  chalk  marl. 

Cenomanien.  Upper  greensand. 

Albien.  Gault. 

Aptien.  Upper  part  of  lower  greensand. 

Neocomien.  Lower  part  of  same. 

Neocomien 

inferieur.  Wealden  beds  and  contemporaneous  marine  strata. 


CH.  XVIL]  CHALK   OF    FAXOE.  239 

the  skeleton  have  been  found.  Such  remains  are  chiefly  met  with 
in  the  soft  freestone,  the  principal  member  of  the  Maestricht  beds. 
Among  the  fossils  common  to  the  Maestricht  and  white  chalk  may  be 
instanced  the  echinoderm  fig.  248. 


Fig.  247. 


Fig.  218. 


Hemipneusti's  radiatus,  Ag. 

Spatangns  radiatus.  Lam. 

Chalk  of  Maestricht  and  white 

chalk. 


Mosasaurus  camperi.    Original  more  than  3  feet  long. 

1  saw  proofs  of  the  previous  denudation  of  the  white  chalk  ex- 
hibited in  the  lower  bed  of  the  Maestricht 
formation  in  Belgium,  about  30  miles  S.W. 
of  Maestricht,  at  the  village  of  Jendrain, 
where  the  base  of  the  newer  deposit  con- 
sisted chiefly  of  a  layer  of  well-rolled, 
black,  chalk-flint  pebbles,  in  the  midst 
of  which  perfect  specimens  of  Thecidea 
radians  and  Belentnites  mucronatus  are 
imbedded. 

Chalk  of  Faxoe.  —  In  the  island  of 
Seeland,  in  Denmark,  the  newest  mem- 
ber of  the  chalk  series,  seen  in  the  sea-cliffs  at  Stevensklint 
resting  on  white  chalk  with  flints,  is  a  yellow  limestone,  a  por- 
tion of  which,  at  Faxoe,  where  it  is  used  as  a  building-stone,  is 
composed  of  corals,  even  more  conspicuously  than  is  usually  ob- 
served in  recent  coral  reefs.  It  has  been  quarried  to  the  depth  of 
more  than  40  feet,  but  its  thickness  is  unknown.  The  imbedded 
shells  are  chiefly  casts,  many  of  them  of  univalve  mollusca,  which 
are  usually  very  rare  in  the  white  chalk  of  Europe.  Thus,  there 
are  two  species  of  Cypr&a,  one  of  Oliva,  two  of  Mitra,  four  of  the 
genus  Cerithium,  six  of  Fusus,  two  of  Trochus,  one  Patella,  one 
Emarginula,  &c. ;  on  the  whole,  more  than  thirty  univalves,  spiral 
or  patelliform.  At  the  same  time,  some  of  the  accompanying  bivalve 
shells,  echinoderms,  and  zoophytes  are  specifically  identical  with 
fossils  of  the  true  Cretaceous  series.  Among  the  cephalopoda  of 
Faxoe  may  be  mentioned  Baculites  Faujasii  and  Belemnites  mucro- 
natus, shells  of  the  white  chalk.  The  Nautilus  Danicus  (see  fig.  249.) 
is  characteristic  of  this  formation  ;  and  it  also  occurs  in  France  in 
the  calcaire  pisolitique  of  Laversin  (dept.  of  Oise). 


240 


WHITE    CHALK. 

Fig.  249. 


[Cn.  XVII. 


Nautilus  Danicus,  Schl.  — Faxoe,  Denmark. 

The  claws  and  entire  skull  of  a  small  crab,  Bra- 
chyurus  rugosus  (Schlottheim),  are  scattered  through 
the  Faxoe  stone,  reminding  us  of  similar  crusta- 
ceans enclosed  in  the  rocks  of  modern  coral  reefs. 
Some  small  portions  of  this  coralline  formation 
consist  of  white  earthy  chalk ;  it  is  therefore  clear 
that  this  substance  must  have  been  produced  simul- 
taneously; a  fact  of  some  importance,  as  bearing 
on  the  theory  of  the  origin  of  white  chalk ;  for  the 
decomposition  of  such  corals  as  we  see  at  Faxoe  is 
capable,  we  know,  of  forming  white  mud,  undistin- 
guishable  from  chalk,  and  which  we  may  suppose  to 
have  been  dispersed  far  and  wide  through  the 
ocean,  in  which  such  reefs  as  that  of  Faxoe  grew. 

White  chalk  (see  Tab.  p.  2,37.  et  seq.\  —  The 
highest  beds  of  chalk  in  England  and  France  consist 
of  a  pure,  white,  calcareous  mass,  usually  too  soft  for 
a  building  stone,  but  sometimes  passing  into  a  more 
solid  state.  It  consists,  almost  'purely,  of  carbo- 
nate of  lime ;  the  stratification  is  often  obscure, 
except  where  rendered  distinct  by  interstratified 
layers  of  flint,  a  few  inches  thick,  occasionally  in 
continuous  beds,  but  oftener  in  nodules,  and  recur- 
ring at  intervals  from  2  to  4  feet  distant  from  each 
other. 

This  upper  chalk  is  usually  succeeded,  in  the 
descending  order,  by  a  great  mass  of  white  chalk 
without  flints,  below  which  comes  the  chalk  marl, 
in  which  there  is  a  slight  admixture  of  argillaceous 
matter.  The  united  thickness  of  the  three  divi- 
sions in  the  south  of  England  equals,  in  some  places, 
1000  feet. 

The  annexed  section  (fig.  250.)  will  show  the 
manner  in  which  the  white  chalk  extends  from 
England  into  France,  covered  by  the  tertiary 
strata  described  in  former  chapters,  and  reposing  on 
lower  cretaceous  beds. 


CH.  XVII.]        ANIMAL    ORIGIN   OP   WHITE    CHALK.  241 

Geographical  extent  and  origin  of  the  White  Chalk.  —  The  area 
over  which  the  white  chalk  preserves  a  nearly  homogeneous  aspect 
is  so  vast,  that  the  earlier  geologists  despaired  of  discovering  any 
analogous  deposits  of  recent  date.  Pure  chalk,  of  nearly  uniform 
aspect  and  composition,  is  met  with  in  a  north-west  and  south-east 
direction,  from  the  north  of  Ireland  to  the  Crimea,  a  distance  of 
about  1140  geographical  miles,  and  in  an  opposite  direction  it  ex- 
tends from  the  south  of  Sweden  to  the  south  of  Bordeaux,  a  distance 
of  about  840  geographical  miles.  In  Southern  Russia,  according  to 
Sir  R.  Murchison,  it  is  sometimes  600  feet  thick,  and  retains  the 
same  mineral  character  as  in  France  and  England,  with  the  same 
fossils,  including  Inoceramus  Cuvieri,  Belemnites  mucronatus,  and 
Ostrea  vesicularis. 

But  it  would  be  an  error  to  imagine,  that  the  chalk  was  ever 
spread  out  continuously  over  the  whole  of  the  space  comprised  within 
these  limits,  although  it  prevailed  in  greater  or  less  thickness  over 
large  portions  of  that  area.  On  turning  to  those  regions  of  the 
Pacific  where  coral  reefs  abound,  we  find  some  archipelagoes  of 
lagoon  islands,  such  as  that  of  the  Dangerous  Archipelago,  for 
instance,  and  that  of  Radack,  with  several  adjoining  groups,  which 
are  from  1100  to  1200  miles  in  length,  and  300  or  400  miles  broad ; 
and  the  space  to  which  Flinders  proposed  to  give  the  name  of  the 
Coralline  Sea  is  still  larger ;  for  it  is  bounded  on  the  east  by  the 
Australian  barrier — all  formed  of  coral  rock, — on  the  west  by  New 
Caledonia,  and  on  the  north  by  the  reefs  of  Louisiade.  Although 
the  islands  in  these  areas  may  be  thinly  sown,  the  mud  of  the  decom- 
posing zoophytes  may  be  scattered  far  and  wide  by  oceanic  currents. 
That  this  mud  would  resemble  chalk  I  have  .already  hinted  when 
speaking  of  the  Faxoe  limestone,  p.  239.,  and  it  was  also  remarked 
in  an  early  part  of  this  volume,  that  even  some  of  that  chalk,  which 
appears  to  an  ordinary  observer  quite  destitute  of  organic  remains, 
is  nevertheless,  when  seen  under  the  microscope,  full  of  fragments  of 
corals,  bryozoa,  and  sponges ;  together  with  the  valves  of  entomo- 
straca,  the  shells  of  foraminifera,  and  still  more  minute  infusoria. 
(See  p.  26.) 

Now  it  had  been  often  suspected,  before  these  discoveries,  that 
white  chalk  might  be  of  animal  origin,  even  where  every  trace  of 
organic  structure  has-  vanished.  This  bold  idea  was  partly  founded 
on  the  fact,  that  the  chalk  consisted  of  carbonate  of  lime,  such  as 
would  result  from  the  decomposition  of  testacea,  echini,  and  corals  ; 
and  partly  on  the  passage  observable  between  these  fossils  when 
half  decomposed  and  chalk.  But  this  conjecture  seemed  to  many 
naturalists  quite  vague  and  visionary,  until  its  probability  was 
strengthened  by  new  evidence  brought  to  light  by  modern  geologists. 

We  learn  from  Captain  Nelson,  that,  in  the  Bermuda  Islands,  and 
in  the  Bahamas,  there  are  many  basins  or  lagoons  almost  sur- 
rounded and  inclosed  by  reefs  of  coral.  At  the  bottom  of  these 
lagoons  a  soft  white  calcareous  mud  is  formed,  not  merely  from  the 
comminution  of  corallines  (or  calcareous  plants)  and  corals,  together 


242  ANIMAL    ORIGIN    OF   WHITE    CHALK.          [Cn.  XVII. 

with  the  exuviae  of  foraminifera,  mollusks,  echinoderms,  and  crusta- 
ceans, but  also,  as  Mr.  Darwin  observed  upon  studying  the  coral 
islands  of  the  Pacific,  from  the  fecal  matter  ejected  by  echinoderms, 
conchs,  and  coral-eating  fish.  In  the  West  Indian  seas,  the  conch 
( Strombus  gigas)  adds  largely  to  the  chalky  mud  by  means  of  its 
faecal  pellets,  composed  of  minute  grains  of  soft  calcareous  matter, 
exhibiting  some  organic  tissue.  Mr.  .Darwin  describes  gregarious 
fishes  of  the  genus  Scarus,  seen  through  the  clear  waters  of  the 
coral  regions  of  the  Pacific  browsing  quietly  in  great  numbers  on 
living  corals,  like  grazing  herds  of  graminivorous  quadrupeds.  On 
Fig.  25i.  opening  their  bodies,  their  intestines  were  found 

to  be  filled  with  impure  chalk.  This  cir- 
cumstance is  the  more  in  point,  when  we  re- 
collect how  the  fossilist  was  formerly  puzzled 
by  meeting,  in  chalk,  with  certain  bodies,  called 
"larch-cones,"  which  were  afterwards  recog- 
nized by  Dr.  Buckland  to  be  the  excrement 
of  fish.  Such  spiral  coprolites  (fig.  251.),  like 
Coproiites  of  fish,  called /*//o  the  scales  and  bones  of  fossil  fish  in  the  chalk, 

eido-copri,  from  the  chalk. 

are  composed  chiefly  of  phosphate  of  lime. 

In  the  Bahamas,  the  angel-fish,  and  the  unicorn  or  trumpet-fish, 
and  many  others,  feed  on  shell-fish,  or  on  corals. 

The  mud  derived  from  the  sources  above  mentioned  may  be  actually 
seen  in  the  Maldiva  Atolls  to  be  washed  out  of  the  lagoons  through 
narrow  openings  leading  from  the  lagoon  to  the  ocean,  and  the 
waters  of  the  sea  are  discoloured  by  it  for  some  distance.  When 
dried,  this  mud  is  very  like  common  chalk,  and  might  probably  be 
made  by  a  moderate  pressure  to  resemble  it  still  more  closely.* 

Mr.  Dana,  when  describing  the  elevated  coral  reef  of  Oahu,  in  the 
Sandwich  Islands,  says  that  some  varieties  of  the  rock  consist  of 
aggregated  shells,  imbedded  in  a  compact  calcareous  base  as  firm  in 
texture  as  any  secondary  limestone ;  while  others  are  like  chalk, 
having  its  colour,  its  earthy  fracture,  its  soft  homogeneous  texture, 
and  being  an  equally  good  writing  material.  The  same  author  de- 
scribes, in  many  growing  coral  reefs,  a  similar  formation  of  modern 
chalk,  undistinguishable  from  the  ancient. f  The  extension,  over  a 
wide  submarine  area,  of  the  calcareous  matrix  of  the  chalk,  as  well  as 
of  the  imbedded  fossils,  would  take  place  more  readily  in  consequence 
of  the  low  specific  gravity  of  the  shells  of  mollusca  and  zoophytes, 
when  compared  with  ordinary  sand  and  mineral  matter.  The  mud 
also  derived  from  their  decomposition  would  be  much  lighter  than 
argillaceous  and  inorganic  mud,  and  very  easily  transported  by  cur- 
rents, especially  in  salt  water. 

Single  pebbles  in  chalk.  —  The  general  absence  of  sand  and  pebbles 
in  the  white  chalk  has  been  already  mentioned ;  but  the  occurrence 
here  and  there,  in  the  south-east  of  England,  of  a  few  isolated  peb- 

*  See  Nelson,  Geol.  Trans.  1837,  vol.        t  Geol.  of  U.  S.  Exploring  Exped. 
v.  p.  108.;  and  Geol.  Quart.  Journ.  1853,     p.  252.  1849. 
p.  200. 


CH.  XVII.]  PEBBLES   IN   CHALK.  243 

bles  of  quartz  and  green  schist,  some  of  them  2  or  3  inches  in 
diameter,  has  justly  excited  much  wonder.  If  these  had  been 
carried  to  the  spots  where  we  now  find  them  by  waves  or  currents 
from  the  lands  once  bordering  the  cretaceous  sea,  how  happened  it 
that  no  sand  or  mud  were  transported  thither  at  the  same  time? 
We  cannot  conceive  such  rounded  stones  to  have  been  drifted  like 
erratic  blocks  by  ice  (see  ch.  x.  and  xi.),  for  that  would  imply 
a  cold  climate  in  the  Cretaceous  period  ;  a  supposition  inconsistent 
with  the  luxuriant  growth  of  large  chambered  univalves,  numerous 
corals,  and  many  fish,  and  other  fossils  of  tropical  forms. 

Now  in  Keeling  Island,  one  of  those  detached  masses  of  coral 
which  rise  up  in  the  wide  Pacific,  Captain  Ross  found  a  single 
fragment  of  greenstone,  where  every  other  particle  of  matter  was 
calcareous  :  and  Mr.  Darwin  concludes  that  it  must  have  come  there 
entangled  in  the  roots  of  a  large  tree.  He  reminds  us  that  Chamisso, 
the  distinguished  naturalist  who  accompanied  Kotzebue,  affirms,  that 
the  inhabitants  of  the  Radack  archipelago,  a  group  of  lagoon  islands 
in  the  midst  of  the  Pacific,  obtained  stones  for  sharpening  their  instru- 
ments by  searching  the  roots  of  trees  which  are  cast  up  on  the  beach.* 

It  may  perhaps  be  objected,  that  a  similar  mode  of  transport 
cannot  have  happened  in  the  cretaceous  sea,  because  fossil  wood  is 
very  rare  in  the  chalk.  Nevertheless  wood  is  sometimes  met  with, 
and  in  the  same  parts  of  the  chalk  where  the  pebbles  are  found,  both 
in  soft  stone  and  in  a  silicified  state  in  flints.  In  these  cases  it  has 
often  every  appearance  of  having  been  floated  from  a  distance,  being 
usually  perforated  by  boring  -shells,  such  as  the  Teredo  and  Fistu- 


The  only  other  mode  of  transport  which  ^suggests  itself  is  sea- 
weed. Dr.  Beck  informs  me  that  in  the  Lym-Fiord,  in  Jutland, 
the  Fucus  vesiculosus,  often  called  kelp,  sometimes  grows  to  the 
height  of  10  feet,  and  the  branches  rising  from  a  single  root  form 
a  cluster  several  feet  in  diameter.  When  the  bladders  are  distended, 
the  plant  becomes  so  buoyant  as  to  float  up  loose  stones  several 
inches  in  diameter,  and  these  are  often  thrown  by  the  waves  high 
up  on  the  beach.  The  Fucus  giganteus  of  Solander,  so  common  in 
Terra  del  Fuego,  is  said  by  Captain  Cook  to  attain  the  length  of  360 
feet,  although  the  stem  is  not  much  thicker  than  a  man's  thumb. 
It  is  often  met  with  floating  at  sea,  with  shells  attached,  several 
hundred  miles  from  the  spots  where  it  grew.  Some  of  these  plants, 
says  Mr.  Darwin,  were  found  adhering  to  large  loose  stones  in  the 
inland  channels  of  Terra  del  Fuego,  during  the  voyage  of  the  Beagle 
in  1834  ;  and  that  so  firmly,  that  the  stones  were  drawn  up  from  the 
bottom  into  the  boat,  although  so  heavy  that  they  could  scarcely  be 
lifted  in  by  one  person.  Some  fossil  sea-weeds  have  been  found 
in  the  Cretaceous  formation,  but  none,  as  yet,  of  large  size. 

But  we  must  not  imagine  that  because  pebbles  are  so  rare  in  the 

•  Darwin,  p.  549.    Kotzebue's  First         f  Mantell,  Geol.  of  S.  E.  of  England, 
Voyage,  vol.  iii,  p.  155.  p.  96. 

R  2 


244  CHALK    FLINTS.  [Cii.  XVII. 

white  chalk  of  England  and  France  there  are  no  proofs  of  sand, 
shingle,  and  clay  having  been  accumulated  contemporaneously 
even  in  European  seas.  The  siliceous  sandstone,  called  "upper 
quader"  by  the  Germans,  overlies  white  argillaceous  chalk  or 
"  planer-kalk,"  a  deposit  resembling  in  composition  and  organic 
remains  the  chalk  marl  of  the  English  series.  This  sandstone  con- 
tains as  many  fossil  shells  common  to  our  white  chalk  as  could  be 
expected  in  a  sea-bottom  formed  of  such  different  materials.  It 
sometimes  attains  a  thickness  of  600  feet,  and  by  its  jointed  structure 
and  vertical  precipices,  plays  a  conspicuous  part  in  the  picturesque 
scenery  of  Saxon  Switzerland,  near  Dresden. 

Chalk  Flints.  —  The  origin  of  the  layers  of  flint,  whether  in 
continuous  sheets  or  in  the  form  of  nodules,  is  more  difficult  to 
explain  than  is  that  of  the  white  chalk.  No  such  siliceous  masses 
are  as  yet  known  to  accompany  the  aggregation  of  chalky  mud  in 
modern  coral  reefs.  The  flint  abounds  mostly  in  the  uppermost 
chalk,  and  becomes  more  rare  or  is  entirely  wanting  as  we  descend ; 
but  this  rule  does  not  hold  universally  throughout  Europe.  Some 
portion  of  the  flint  may  have  been  derived  from  the  decomposition 
of  sponges  and  other  zoophytes  provided  with  siliceous  skeletons  ; 
for  it  is  a  fact,  that  siliceous  spiculae,  or  the  minute  bones  of  sponges, 
are  often  met  with  in  flinty  nodules,  and  may  have  served  at  least  as 
points  of  attraction  to  some  of  the  siliceous  matter  when  it  was  in  the 
act  of  separating  from  chalky  mud  during  the  process  of  solidification. 
But  there  are  other  copious  sources  before  alluded  to,  whence  the 
waters  of  the  ocean  derive  a  constant  supply  of  silex  in  solution,  such 
as  the  decomposition  of  felspathic  rock  (see  p.  42.),  also  mineral 
springs  rising  up  in  the  bed  of  the  sea,  especially  those  of  a 
high  temperature ;  since  their  waters,  if  chilled  when  first  mingling 
with  the  sea,  would  readily  precipitate  siliceous  matter  (see  above, 
p.  42.).  Nevertheless,  the  occurrence  in  the  white  chalk  of  beds  of 
nodular  or  tabular  flint  at  so  many  distinct  levels,  implies  a  peri- 
odical action  throughout  wide  oceanic  areas  not  easily  accounted  for. 
It  seems  as  if  there  had  been  time  for  each  successive  accumulation 
of  calcareo-siliceous  mud  to  become  partially  consolidated,  and  for  a 
re-arrangement  of  its  particles  to  take  place  (the  heavier  silex  sink- 
ing to  the  bottom)  before  the  next  stratum  was  superimposed ;  a 
process  formerly  suggested  by  Dr.  Buckland.* 

A  more  difficult  enigma  is  presented  by  the  occurrence  of  certain 
huge  flints,  or  potstones  as  they  are  called  in  Norfolk,  occurring 
singly,  or  arranged  in  nearly  continuous  columns  at  right  angles  to 
the  ordinary  and  horizontal  layers  of  small  flints.  I  visited,  in 
the  year  1825,  an  extensive  range  of  quarries  then  open  on  the  river 
Bure,  near  Horstead,  about  six  miles  from  Norwich,  which  afforded 
a  continuous  section,  a  quarter  of  a  mile  in  length,  of  white  chalk, 
exposed  to  the  depth  of  26  feet,  and  covered  by  a  thick  bed  of 
gravel.  The  potstones,  many  of  them  pear-shaped,  were  usually 

*  Geol.  Trans.,  First  series,  vol.  iv.  p.  413. 


CH.  XVII.]  POTSTONES   AT    HORSTEAD.  245 

about  three  feet  in  height,  and  one  foot  in  their  transverse  diameter, 
placed  in  vertical  rows,  like  pillars  at  irregular  distances  from  each 

Fig.  252. 


From  a  drawing  by  Mrs.  Gunn. 
View  of  a  chalk  pit  at  Horstead,  near  Norwich,  showing  the  position  of  the  potstones. 

other,  but  usually  from  20  to  30  feet  apart,  though  sometimes  nearer 
together,  as  in  the  above  sketch.  These  rows  did  not  terminate 
downwards  in  any  instance  which  I  could  examine,  nor  upwards, 
except  at  the  point,  where  they  were  cut  off  abruptly  by  the  bed  of 
gravel.  On  breaking  open  the  potstones,  I  found  an  internal  cylin- 
drical nucleus  of  pure  chalk,  much  harder  than  the  ordinary  sur- 
rounding chalk,  and  not  crumbling  to  pieces  like  it,  when  exposed  to 
the  winter's  frost.  At  the  distance  of  half  a  mile,  the  vertical  piles 
of  potstones  were  much  farther  apart  from  each  other.  Dr.  Buckland 
has  described  very  similar  phenomena  as  characterizing  the  white 
chalk  on  the  north  coast  of  Antrim,  in  Ireland.* 

FOSSILS   OF   THE   UPPER   CRETACEOUS   ROCKS. 

Among  the  fossils  of  the  white  chalk,  echinoderms  are  very  nu- 

Fig.  253. 


Ananchytes  ovatus.    White  chalk,  upper  and  lower. 

a.  Side  view. 

b.  Bottom  of  the  shell  on  which  both  the  oral  and  anal  apertures  are  placed ; 

the  anal  being  more  round,  and  at  the  smaller  end. 

Geol.  Trans.,  First  series,  vol.  iv.  p.  413.,  *'  On  Paramoudra,  &c.' 
R  3 


246 


FOSSILS   OF    UPPER   CRETACEOUS   ROCKS.        [Cn.  XVII. 


merous ;    and  some  of  the  genera,  like  Ananchytes  (see  fig.  253. ), 
are  exclusively  cretaceous.     Among  the  Crinoidea,  the  Marsupite 

Fig.  255. 


Micrastes  cor  ansumum. 
White  chalk. 


Galerites  albogalerus,  Lara. 
White  chalk. 


(fig.  260.)  is  a  characteristic  genus.  Among  the  mollusca,  the  cepha- 
lopoda, or  chambered  univalves,  of  the  genera  Ammonite,  Scaphite, 
Belemnite,  (fig.  256.)  Baculite,  (257.— 259.)  and  Turrilite,  (262,  263.) 
with  other  allied  forms,  present  a  great  contrast  to  the  testacea  of 
the  same  class  in  the  tertiary  and  recent  periods. 

Fig.  256. 


a.  Belemnites  mucronatus. 

b.  Same,  showing  internal  structure.  Maestricht,  Faxoe,  and  white  chalk. 

Fig.  257. 


Baculites  anceps.    Upper  green  sand,  or  chloritic  marl,  crate  chloride.    France. 
A.  D'Orb.  Terr.  Cret. 


Fig.  258. 


Fig.  259. 


Portion  of  Baculites  Fanjasii. 
Maestricht  and  Faxoe  beds  and  white  chalk. 

Fig.  260. 


Portion  of  JSaculites  anceps. 
Maestricht  and  Faxoe  beds  and  white  chalk. 

Fig.  261. 


Marsupiles  MiUeri. 
White  chalk. 


Scaphites  cequalis.    Chloritic 

marl  of  Upper  Green  Sand, 

Dorsetshire. 


CH.  XVI'L]      FOSSILS   OP   UPPER   CRETACEOUS   ROCKS. 

Fig.  262.  Fig.  263. 


247 


a.  Fragment  of  Turrilites  costalus, 
Chalk  marl.. 


Turrilites  costatus. 
Chalk 


6.  Same,  showing  the  indented  border 
of  the  partition  of  the  chambers. 


Among  the  brachiopoda  in  the  white  chalk,  the   Terebratulce  are 
very  abundant.     These  shells  are  known  to  live  at  the  bottom  of  the 


Fig.  264. 


Fig.  265. 


Fig.  266. 


Fig.  267. 


Terebratula  Defrancfi.  Terebratula 

Upper  white  chalk.  octoplicata. 

(V&r.ofT.plicatilis.) 
Upper  white  chalk. 


Terebratula  pumilus. 

(Magas pumilus,  Sow.) 

Upper  white  chalk. 


Terebratula 

cornea. 
Upper  white  chalk. 


sea,  where  the  water  is  tranquil  and  of  some  depth  (see  figs.  264, 
265,  266,  267,  268.).     With  these  are  associated  some  forms  of  oyster 


Fig.  268. 


Terebratula  biplicata, 
Sow.    Upper  cretaceous. 


Fig.  269 


Fig.  270. 


Crania  Parisiensts, 
inferior  or  attached 

valve. 
Upper  white  chalk. 


Pecten  Beaveri,  reduced  to 

one-third  diameter. 

Lower  white  chalk  and  chalk 

marl.    Maidstone. 


(see  figs.  275,  276,  277.),  and  other  bivalves  (figs.  269,  270,  271, 
272,  273.). 

Among  the  bivalve  mollusca,  no  form  marks  the  cretaceous  era  in 
Europe,  America,  and  India  in  a  more  striking  manner  than  the 
extinct  genus  Inoceramus  (Catillus  of  Lam. :  see  fig.  274.),  the  shells 


R   4 


248 


FOSSILS   OP   UPPER   CRETACEOUS   ROCKS.       [Cn.  XVII. 


of  which  are  distinguished  by  a  fibrous  texture,  and  are  often  met 
with  in  fragments,  having,  probably,  been  extremely  friable. 


Fig.  271. 


Pecten  5-costatus. 

White  chalk,  upper  and 

lower  greensands. 


Fig.  272. 


Plagtostoma  Hoperi,  Sow. 

Syn.  Lima  Hoperi. 

White  cnalk  and  upper 

greensand. 


Fig.  273. 


Plagt'ostoma  spinosum,  Sow. 

Syn.  Spondylus  spinosus. 

Upper  white  chalk. 


Of  the  singular  family  called  Rudistes,  by  Lamarck,  hereafter  to 
be  mentioned  as  extremely  characteristic  of  the  chalk  of  Southern 


Fig.  274. 


Fig.  275. 


Inoceramus  LamarcMi. 

Syn.  Catillus  Lamarchii. 

White  Chalk  (Dixon's  Geol.  Sussex.  Tab.  28. 

tig.  29.). 


Ostrea  v estcularis.    Syn.  Grypheca  globosa. 
Upper  chalk  and  upper  greensand. 


Europe,  a  single  representative  only  (fig.  278.)  has  been  discovered  in 
the  white  chalk  of  England. 


Fig.  276. 


Fig.  277. 


Ostrea  columba. 

Ryn .  Gryphtea  colinnba. 

Upper  greensand. 


Ostrea  carinata.    Chalk  marl,  upper  and 
lower  greensand. 


CH.  XVIL]  MOLLUSC  A,    BRYOZOA,    SPONGES. 

Fig.  279. 


249 


Radiolites  Mortoni,  Mantell.    Houghton,  Sussex.    White  chalk. 

Diameter  one-seventh  nat.  size. 
Fig.  278.  Two  individuals  deprived  of  their  upper  valves,  adhering  together. 

279.  Same  seen  from  above. 

280.  Transverse  section  of  part  of  the  wall  of  the  shell,  magnified  to  show  the  structure. 

281.  Vertical  section  of  the  same. 

On  the  side  where  the  shell  it  thinnest,  there  is  one  external  furrow  and  corresponding  internal 
ridge,  a,  b,  figs.  278,  279.;  but  they  are  usually  less  prominent  than  in  these  figures.  This  species 
was  first  referred  by  Mantell  to  Hippurites,  afterwards  to  the  genus  Radiolites.  I  have  never  seen 
the  upper  valve.  The  specimen  above  figured  was  discovered  by  the  late  Mr.  Dixon. 

With  these  mollusca  are  associated  many  Bryozoa,  such  as  Es- 
chara  and  Escharina   (figs.  282,  283.),   which   are  alike   marine, 

Fig.  282. 


Eschara  disticha. 
a.  Natural  size. 
6.  Portion  magnified. 
White  chalk. 


Fig.  283. 


Fig.  284. 


Escharina  oceani. 

a.  Natural  size. 

b.  Part  of  the  same  magnified.    White 

chalk. 


Ventricutiles  radiatus, 

Mantell. 

Syn.  Ocellaria  radiata, 
D'Orb.    White  chalk. 


and,  for  the  most  part,  indicative  of  a  deep  sea.     These  and  other 
organic  bodies,  especially  sponges,  such  as    Ventriculites  (fig.  284. 


250 


FOSSILS   OF    UPPER   CRETACEOUS   BEDS.       [Ca  XVII. 


and  Siphonia  (fig.  286.),  are  dispersed  indifferently  through  the 
soft  chalk  and  hard  flint,  and  some  of  the  flinty  nodules  owe  their  ir- 
regular forms  to  inclosed  sponges,  such  as  fig.  285.  «.,  where  the  hol- 
lows in  the  exterior  are  caused  by  the  branches  of  a  sponge,  seen  on 
breaking  open  the  flint  (fig.  285.  &.). 

Fig.  286. 


Fig.  285. 


A  branching  sponge  in  a  flint,  from  the  white  chalk. 
From  the  collection  of  Mr.Bowerbank. 


The  remains  of  fishes  of  the  Upper  Cretaceous  formations  consist 
chiefly  of  teeth  of  the  shark  family  of  genera,  in  part  common  to  the 


Fig.  287. 


Palatal  tooth  of 

Ptychodut  dccurrens. 

Lower  white  chalk. 

Maidstone. 


Cestracion  Phillippi ;  recent. 
Port  Jackson.    Bucklaud,  Bridgewater  Treatise,  pi.  27.  d. 


tertiary,  and   partly   distinct.     To   the    latter    belongs    the   genus 
Ptychodus  (fig.  287.),  which  is  allied  to  the  living  Port  Jackson 


CH.  XVII.]          UPPER  GREEN  SAND.  251 

Shark,  Cestracion  Phillippi,  the  anterior  teeth  of  which  (see  fig.  288.  a) 
are  sharp  and  cutting,  while  the  posterior  or  palatal  teeth  (b)  are  flat, 
and  analogous  to  the  fossil  (fig.  287.). 

But  we  meet  with  no  bones  of  land  animals,  nor  any  terrestrial 
or  fluviatile  shells,  nor  any  plants,  except  sea-weeds,  and  here  and 
there  a  piece  of  drift  wood.  All  the  appearances  concur  in  leading 
us  to  conclude  that  the  white  chalk  was  the  product  of  an  open  sea 
of  considerable  depth. 

The  existence  of  turtles  and  oviparous  saurians,  and  of  a  Ptero- 
dactyl or  winged-lizard,  found  in  the  white  chalk  of  Maidstone,  im- 
plies, no  doubt,  some  neighbouring  land;  but  a  few  small  islets  in 
mid-ocean,  like  Ascension,  formerly  so  much  frequented  by  migratory 
droves  of  turtle,  might  perhaps  have  afforded  the  required  retreat 
where  these  creatures  laid  their  eggs  in  the  sand,  or  from  which 
the  flying  species  may  have  been  blown  out  to  sea.  Of  the  vegetation 
of  such  islands  we  have  scarcely  any  indication,  but  it  consisted 
partly  of  cycadeous  plants  ;  for  a  fragment  of  one  of  these  was  found 
by  Capt.  Ibbetson  in  the  chalk  marl  of  the  Isle  of  Wight,  and  is 
referred  by  A.  Brongniart  to  Clathraria  Lyellii,  Mantell,  a  species 
common  to  the  antecedent  Wealden  period. 

The  Pterodactyl  of  the  Kentish  chalk,  above  alluded  to,  was  of 
gigantic  dimensions,  measuring  16  feet  6  inches  from  tip  to  tip  of  its 
outstretched  wings.  Some  of  its  elongated  bones  were  at  first  mis- 
taken by  able  anatomists  for  those  of  birds  ;  of  which  class  no  osseous 
remains  seem  as  yet  to  have  been  derived  from  the  chalk,  or  indeed 
from  any  secondary  or  primary  formation,  except  perhaps  the  Wealden. 

Upper  greensand  (Table,  p.  105.  &c.). — The  lower  chalk  without 
flints  passes  gradually  downwards,  in  the  south  of  England,  into  an 
argillaceous  limestone,  "the  chalk  marl,"  already  alluded  to,  in 
which  ammonites  and  other  cephalopoda,  so  rare  in  the  higher  parts 
of  the  series,  appear.  This  marly  deposit  passes  in  its  turn  into  beds 
called  the  Upper  Greensand,  containing  green  particles  of  sand 
of  a  chloritic  mineral.  In  parts  of  Surrey,  calcareous  matter  is 
largely  intermixed,  forming  a  stone  called  Jlrestone.  In  the  cliffs 
of  the  southern  coast  of  the  Isle  of  Wight,  this  upper  greensand  is 
100  feet  thick,  and  contains  bands  of  siliceous  limestone  and  calca- 
reous sandstone  with  nodules  of  chert. 

The  Upper  Greensand  is  regarded  by  Mr.  Austen  and  Mr.  D. 
Sharpe,  as  a  littoral  deposit  of  the  Chalk  Ocean,  and,  therefore,  con- 
temporaneous with  part  of  the  chalk  marl,  and  even,  perhaps,  with 
some  part  of  the  white  chalk.  For  as  the  land  went  on  sinking,  and 
the  cretaceous  sea  widened  its  area,  white  mud  and  chloritic  sand 
were  always  forming  somewhere,  but  the  line  of  sea-shore  was 
perpetually  varying  its  position.  Hence,  though  both  sand  and 
mud  originated  simultaneously,  the  one  near  the  land,  the  other  far 
from  it,  the  sands  in  every  locality  where  a  shore  became  submerged, 
might  constitute  the  underlying  deposit. 

Gault. — The  lowest  member  of  the  upper  Cretaceous  group,  usually 
about  100  feet  thick  in  the  S.E.  of  England,  is  provincially  termed 


252 


THE    BLACKDOWN    BEDS. 


[Cn.  XVII. 

Gault.     It  consists  of  a  dark  blue  marl,  sometimes  intermixed  with 
greensand.    Many  peculiar  forms  of  cephalopoda,  such  as  the  Hamite 


Fossils  of  the  Upper  Greensand. 
Fig.  289. 


Fig.  290. 


Terebratula  lyra.        7  Upper  greensand. 
.  J     France. 


6.  Same,  seen  in  profile. 


Ammonites  Rhotomagcnsis* 
Upper  greensand. 


Fig.  '291. 


Hamites  spiniger  (Fitton)  ;  near  Folkstone.    Gault. 

(fig.  291.)  and  Scaphite,  with  other  fossils,  characterize  this  form- 
ation, which,  small  as  is  its  thickness,  can  be  traced  by  its  organic 
remains  to  distant  parts  of  Europe,  as,  for  example,  to  the  Alps. 

The  Blackdown  beds  in  Dorsetshire,  celebrated  for  containing 
many  species  of  fossils  not  found  elsewhere,  have  been  commonly 
referred  to  the  Upper  Greensand,  which  they  resemble  in  mineral 
character;  but  Mr.  Sharpe  has  suggested,  and  apparently  with 
reason,  that  they  are  rather  the  equivalent  of  the  Gault,  and  were 
probably  formed  on  the  shore  of  the  sea,  in  the  deeper  parts  of 
which  the  fine  mud  called  Gault  was  deposited.  Several  Blackdown 
species  are  common  to  the  Lower  cretaceous  series,  as,  for  ex- 
ample, Trigonia  caudata,  fig.  299.  We  learn  from  M.  D'Archiac, 
that  in  France,  at  Mons,  in  the  valley  of  the  Loire,  strata  of  green- 
sand  occur  of  the  same  age  as  the  Blackdown  beds,  and  containing 
many  of  the  same  fossils.  They  are  also  regarded  as  of  littoral 
origin  by  M.  D'Archiac.* 

The  phosphate  of  lime,  found  near  Farnham,  in  Surrey,  in  such 
abundance  as  to  be  used  largely  by  the  agriculturist  for  fertilizing 
soils,  occurs  exclusively,  according  to  Mr.  R.  A.  C.  Austen,  in  the 
upper  greensand  and  gault.  It  is  doubtless  of  animal  origin,  and 
partly  coprolitic,  probably  derived  from  the  excrement  of  fish. 

*  Hist,  des  Progres  de  la  Geol.,  &c.,  vol.  iv.  p.  360.,  1851. 


CH.  XVII.] 


HIPPURITE    LIMESTONE. 


253 


HIPPURITE    LIMESTONE. 

Difference  between  the  chalk  of  the  north  and  south  of  Europe.  — 
By  the  aid  of  the  three  tests  of  relative  age,  namely,  superposition, 
mineral  character,  and  fossils,  the  geologist  has  been  enabled  to  refer 
to  the  same  Cretaceous  period  certain  rocks  in  the  north  and  south 
of  Europe,  which  differ  greatly,  both  in  their  fossil  contents  and  in 
their  mineral  composition  and  structure. 

If  we  attempt  to  trace  the  cretaceous  deposits  from  England  and 
France  to  the  countries  bordering  the  Mediterranean,  we  perceive, 
in  the  first  place,  that  the  chalk  and  greensand  in  the  neighbourhood 
of  London  and  Paris  form  one  great  continuous  mass,  the  Straits  of 
Dover  being  a  trifling  interruption,  a  mere  valley  with  chalk  cliffs  on 
both  sides.  We  then  observe  that  the  main  body  of  the  chalk  which 
surrounds  Paris  stretches  from  Tours  to  near  Poitiers  (see  the  annexed 

map,  fig.  292.,  in  which  the  shaded  part 
Fis- 292-  represents  chalk). 

Between  Poitiers  and  La  Rochelle, 
the  space  marked  A  on  the  map  sepa- 
rates two  regions  of  chalk.  This  space 
is  occupied  by  the  Oolite  and  certain 
other  formations  older  than  the  Chalk, 
and  has  been  supposed  by  M.  E.  de 
Beaumont  to  have  formed  an  island  in 
the  cretaceous  sea.  South  of  this  space 
we  again  meet  with  a  formation  which 
we  at  once  recognize  by  its  mineral 
character  to  be  .chalk,  although  there 
are  some  places  where  the  rock  becomes 
oolitic.  The  fossils  are,  upon  the  whole, 
very  similar ;  especially  certain  species 
of  the  genera  Spatangus,  Ananchytes, 
Cidarites,  Nucula,  Ostrea,  Gryphaa 
(Exogyra))  Pecten,  Plagiostoma  (Lima), 
Trigonia,  Catillus  (Inoceramus\  and 
Terebratula.*  But  Ammonites,  as  M. 
d'Archiac  observes,  of  which  so  many  species  are  met  with  in  the 
chalk  of  the  north  of  France,  are  scarcely  ever  found  in  the  southern 
region ;  while  the  genera  Hamite,  Turrilite,  and  Scaphite,  and  per- 
haps Belemnite,  are  entirely  wanting. 

On  the  other  hand,  certain  forms  are  common  in  the  south  which 
are  rare  or  wholly  unknown  in  the  north  of  France.  Among  these 
may  be  mentioned  many  Hippurites,  Sphcerulites,  and  other  mem- 
bers of  that  great  family  of  mollusca  called  Rudistes  by  Lamarck,  to 
which  nothing  analogous  has  been  discovered  in  the  living  creation, 
but  which  is  quite  characteristic  of  rocks  of  the  Cretaceous  era  in 


*  D'Archiac,  sur  la  Form.  Cretacee  du  S.  0.  de  la  France,  Mem.  de  la  Soc.  Geol. 
do  France,  torn.  ii. 


254 


CHALK   OF    SOUTH   OF    EUROPE. 


[CH.  XVII. 

the  south  of  France,  Spain,  Sicily,  Greece,  and  other  countries  border- 
ing the  Mediterranean. 

Fig.  293.  Fig.  294. 

a  b 


a.  Radiolites  radiosus,  D'Orb.    (Hippurftes,  Lam.) 
6.  Upper  valve  of  same. 

White  chalk  of  France. 


Fig.  295. 


Radiolites  fuliaceus,  D '  O  rb. 
Syn.  Sphcerufi/es  agarici- 

formis,  Blainv. 
White  chalk  of  France. 


Hippurites  organisans,  Desmoulins, 

Upper  chalk:  —chalk  marl  of  Pyrenees  ?* 

0.  Young  individual ;  when  full  grown  they  occur  in  groups  adhering 

laterally  to  each  other. 

6.  Upper  side  of  the  upper  valve,  showing  a  reticulated  structure  in 
those  parts,  b,  where  the  external  coating  is  worn  off. 

c.  Upper  end  or  opening  of  the  lower  and  cylindrical  valve 

d.  Cast  of  the  interior  of  the  lower  conical  valve. 

The  species  called  Hippurites  organisans  (fig.  295.)  is  more  abun- 
dant than  any  other  in  the  south  of  Europe  ;  and  the  geologist  should 
make  himself  well  acquainted  with  the  cast  d,  which  is  far  more 
common  in  many  compact  marbles  of  the  upper  cretaceous  period 
than  the  shell  itself,  this  having  often  wholly  disappeared.  The 
flutings,  or  smooth,  rounded,  longitudinal  ribs,  representing  the  form 
of  the  interior,  are  wholly  unlike  the  Hippurite  itself,  and  in  some 
individuals  attain  a  great  size  and  length. 

Between  the  region  of  chalk  last  mentioned,  in  which  Perigueux 
is  situated,  and  the  Pyrenees,  the  space  B  intervenes.  (See  Map, 


*  D'Orbigny's  PaLeontologie  Frai^aise,  pi.  533. 


CH.  XVII.]  CRETACEOUS  HOCKS.  255 

fig.  292.).  Here  the  tertiary  strata  cover,  and  for  the  most  part  con- 
ceal, the  cretaceous  rocks,  except  in  some  spots  where  they  have  been 
laid  open  by  the  denudation  of  the  newer  formations.  In  these  places 
they  are  seen  still  preserving  the  form  of  a  white  chalky  rock,  which 
is  charged  in  part  with  grains  of  greensand.  Even  as  far  south  as 
Tercis,  on  the  Adour,  near  Dax,  cretaceous  rocks  retain  this  cha- 
racter where  I  examined  them  in  1828,  and  where  M.  Grateloup 
has  found  in  them  Ananchytes  ovata  (fig.  253.),  and  other  fossils  of 
the  English  chalk,  together  with  Hippurit.es. 

CRETACEOUS   ROCKS   IN   THE   UNITED   STATES. 

If  we  pass  to  the  American  continent,  we  find  in  the  state  of  New 
Jersey  a  series  of  sandy  and  argillaceous  beds  wholly  unlike  our  Upper 
Cretaceous  system ;  which  we  can,  nevertheless,  recognize  as  refer- 
able, paleontologically,  to  the  same  division. 

That  they  were  about  the  same  age  generally  as  the  European 
chalk  and  greensand,  was  the  conclusion  to  which  Dr.  Morton  and 
Mr.  Conrad  came  after  their  investigation  of  the  fossils  in  1834. 
The  strata  consist  chiefly  of  greensand  and  green  marl,  with  an  over- 
lying coralline  limestone  of  a  pale  yellow  colour,  and  the  fossils,  on 
the  whole,  agree  most  nearly  with  those  of  the  upper  European  series, 
from  the  Maestricht  beds  to  the  gault  inclusive.  I  collected  sixty 
shells  from  the  New  Jersey  deposits  in  1841,  five  of  which  were  iden- 
tical with  European  species  —  Ostrea  larva,  0.  vesicularis,  Gryphasa 
costata,  Pecten  quinque-costatus,  Belemnites  mucronatus.  As  some 
of  these  have  the  greatest  vertical  range  in  Europe,  they  might  be 
expected  more  than  any  others  to  recur  in  distant  parts  of  the  globe. 
Even  where  the  species  are  different,  the  generic  forms,  such  as  the 
Baculite  and  certain  sections  of  Ammonites,  as  also  the  Inoceramus 
(see  above,  fig.  274.)  and  other  bivalves,  have  a  decidedly  cretaceous 
aspect.  Fifteen  out  of  the  sixty  shells  above  alluded  to  were  regarded 
by  Professor  Forbes  as  good  geographical  representatives  of  well- 
known  cretaceous  fossils  of  Europe.  The  correspondence,  therefore, 
is  not  small,  when  we  reflect  that  the  part  of  the  United  States  where 
these  strata  occur  is  between  3000  and  4000  miles  distant  from  the 
chalk  of  Central  and  Northern  Europe,  and  that  there  is  a  difference 
of  ten  degrees  in  the  latitude  of  the  places  compared  on  opposite  sides 
of  the  Atlantic.* 

Fish  of  the  genera  Lamna,  Galeus,  and  Carcharodon  are  common 
to  New  Jersey  and  the  European  cretaceous  rocks.  So  also  is  the 
genus  Mosasaurus  among  reptiles.  The  vertebra  of  a  Plesiosaurus, 
a  reptile  known  in  the  English  chalk,  had  often  been  cited  on  the 
authority  of  Dr.  Harlan  as  occurring  in  the  cretaceous  marl,  at 
Mullica  Hill,  in  New  Jersey.  But  Dr.  Leidy  has  since  shown  that 
the  bone  in  question  is  not  saurian  but  cetaceous,  and  whether  it  can 
truly  lay  claim  to  the  high  antiquity  assigned  to  it,  is  a  point  still 
open  to  discussion.  The  discovery  of  another  mammal  of  the  seal 

*  See  a  paper  by  the  author,  Quart.  Journ.  Geol.  Soc.  vol.  i.  p.  79. 


256  CRETACEOUS  ROCKS.  CH.  XVII. 

tribe  (  Stenorhynchus  vetus,  Leidy),  from  a  lower  bed  in  the  cretaceous 
series  in  New  Jersey,  appears  to  rest  on  better  evidence.* 

From  New  Jersey  the  cretaceous  formation  extends  southwards  to 
North  Carolina  and  Georgia,  cropping  out  at  intervals  from  beneath 
the  tertiary  strata,  between  the  Appalachian  Mountains  and  the 
Atlantic.  They  then  sweep  round  the  southern  extremity  of  that 
chain,  in  Alabama  and  Mississippi,  and  stretch  northwards  again  to 
Tennessee  and  Kentucky.  They  have  also  been  traced  far  up  the 
valley  of  the  Missouri,  as  far  north  as  lat.  48°,  or  to  Fort  Mandan  ; 
so  that  already  the  area  which  they  are  ascertained  to  occupy  in 
North  America  may  perhaps  equal  their  extent  in  Europe,  and 
exceeds  that  of  any  other  fossiliferous  formation  in  the  United 
States.  So  little  do  they  resemble  mineralogically  the  European 
white  chalk,  that  in  North  America,  limestone  is  upon  the  whole,  an 
exception  to  the  rule  ;  and,  even  in  Alabama,  where  I  saw  a  calca- 
reous member  of  this  group,  composed  of  marl-stone,  it  was  more 
like  the  English  and  French  Lias  than  any  other  European  secondary 
deposit. 

At  the  base  of  the  system  in  Alabama,  I  found  dense  masses  of 
shingle,  perfectly  loose  and  unconsolidated,  derived  from  the  waste  of 
paleozoic  (or  carboniferous)  rocks,  a  mass  in  no  way  distinguishable, 
except  by  its  position,  from  ordinary  alluvium,  but  covered  with 
marls  abounding  in  Inocerami. 

In  Texas,  according  to  F.  Homer,  the  chalk  assumes  a  new  litho- 
logical  type,  a  large  portion  of  it  consisting  of  hard  siliceous  lime- 
stone, but  the  organic  remains  leave  no  doubt  in  regard  to  its  age,  the 
Baculites  anceps  and  ten  other  European  species  occurring  there. 

In  South  America  the  cretaceous  strata  have  been  discovered  in 
Columbia,  as  at  Bogota  and  elsewhere,  containing  Ammonites,  Ha- 
mites,  Inocerami,  and  other  characteristic  shells.f 

In  the  South  of  India,  also,  at  Pondicherry,  Verdachellum,  and 
Trinconopoly,  Messrs.  Kaye  and  Egerton  have  collected  fossils  be- 
longing to  the  cretaceous  system.  Taken  in  connection  with  those 
from  the  United  States,  they  prove,  says  Prof.  E.  Forbes,  that  those 
powerful  causes  which  stamped  a  peculiar  character  on  the  forms  of 

*  In  the  Principles  of  Geology,  ninth  makes  the  point  rather  doubtful.     The 

ed.  p.  145.,  I  cited  Dr.  Leidy  of  Phi-  tooth  of  Stenorhynchus  vetus,  figured  by 

ladelphia    as    having    described  (Pro-  Leidy    from    a    drawing    of   Conrad's 

ceedings  of   Acad.   Nat.   Sci.   Philad.,  (Proceed,  of  Acad.   Nat.   Sci.   Philad. 

1851)  two  species  of  cetacea  of  a  new  1853,  p.  377.),  was  found  by  Samuel  K. 

genus  which  he  called  Priscodelphinus,  Wetherill,  Esq.,  in  the  greensand  l£  miles 

from  the  greensand  of  New  Jersey.     In  south-east  of  Burlington.     This  gentle- 

1853, 1  saw  the  two  vertebra  at  Phila-  man  related  to  me  and  Mr.  Conrad,  in 

delphia  on  which  this  new  genus  was  1853,  the  circumstances  under  which  he 

founded,  and  afterwards,  with  the  aid  of  met  with  it,  associated  with  Ammonites 

Mr.  Conrad,  traced  one  of  them  to  a  placenta,       Ammonites       Delawarensis, 

Miocene  marl  pit  in  Cumberland  county  Trigonia  thoracica,  &c.     The  tooth  has 

New  Jersey.  The  other  (the  Plesiosaurus  been  mislaid,  but  not  until  it  had  excited 

of  Harlan),  labelled  "  Mullica  Hill "  in  much  interest  and  had  been  carefully 

the  Museum,  would  no  doubt  be  an  upper  examined  by  good  zoologists, 
cretaceous  fossil,  if  really  derived  from        f  Proceedings  of  the  Geol.  Soc.  vol.  iv. 

that  locality,  but  its  mineral  condition  p.  391. 


CH.  XVIII.]  LOWER   GREENSAND.  257 

marine  animal  life  at  this  period,  exerted  their  full  intensity  through 
the  Indian,  European,  and  American  seas.  *  Here,  as  in  North  and 
South  America,  the  cretaceous  character  can  be  recognized  even 
where  there  is  no  specific  identity  in  the  fossils  ;  and  the  same  may 
be  said  of  the  organic  type  of  those  rocks  in  Europe  and  India  which 
occur  next  to  the  chalk  in  the  ascending  and  descending  order, 
namely  the  Eocene  and  the  Oolitic. 


CHAPTER  XVHI. 

LOWER  CRETACEOUS   AND   WEALDEN   FORMATIONS. 

Lower  Greensand — Term  "Neocomian" — Atherfield  section,  Isle  of  Wight — 
Fossils  of  Lower  Greensand  — Wealden  Formation  — Freshwater  strata  in- 
tercalated between  two  marine  groups  —  Weald  Clay  and  Hastings  Sand  — 
Fossil  shells,  fish,  and  plants  of  Wealden — Their  relation  to  the  Cretaceous 
type  —  Geographical  extent  of  Wealden  —  Movements  in  the  earth's  crust  to 
which  the  Wealden  owed  its  origin  and  submergence — Flora  of  the  Lower 
Cretaceous  and  Wealden  Periods. 

THE  term  "  Lower  Greensand  "  has  hitherto  been  most  commonly 
applied  to  such  portions  of  the  Cretaceous  series  as  are  older  than  the 
Gault.  But  the  name  has  often  been  complained  of  as  inconvenient, 
and  not  without  reason,  since  green  particles  are  wanting  in  a  large 
part  of  the  strata  so  designated,  even  in  England,  and  wholly  so  in 
some  European  countries.  Moreover,  a  subdivision  of  the  Upper 
Cretaceous  group  has  likewise  been  called  Greensand,  and  to  prevent 
confusion  the  terms  Upper  and  Lower  Greensand  were  introduced. 
Such  a  nomenclature  naturally  leads  the  uninitiated  to  suppose  that 
the  two  formations  so  named  are  of  somewhat  co-ordinate  value,  which 
is  so  far  from  being  true,  that  the  Lower  Greensand,  in  its  widest 
acceptation,  embraces  a  series  nearly  as  important  as  the  whole  Upper 
Cretaceous  group,  from  the  Gault  to  the  Maestricht  beds  inclusive ; 
while  the  Upper  Greensand  is  but  one  subordinate  member  of  this 
same  group.  Many  eminent  geologists  have,  therefore,  proposed  the 
term  "  Neocomian "  as  a  substitute  for  Lower  Greensand ;  because, 
near  Neufchatel  (Neocomum),  in  Switzerland,  these  Lower  Green- 
sand  strata  are  well  developed,  entering  largely  into  the  structure  of 
the  Jura  mountains.  By  the  same  geologists  the  Wealden  beds  are 
usually  classed  as  "  Lower  Neocomian,"  a  classification  which  will 
not  appear  inappropriate  when  we  have  explained,  in  the  sequel,  the 
intimate  relation  of  the  Lower  Greensand  and  Wealden  fossils. 

Dr.  Fitton,  to  whom  we  are  indebted  for  an  excellent  monograph 
on  the  Lower  Cretaceous  Cor  Greensand)  formation  as  developed  in 

*  See  Forbes,  Quart.  Geol.  Journ.  vol.  i.  p.  79. 
8 


258  ATHERFIELD  SECTION,  ISLE    OF    WIGHT.        [Cn.  XVIII. 

England,  gives  the  following  as  the  succession  of  rocks  seen  in  parts 
of  Kent. 

No.  1.  Sand,  white,  yellowish,  or  ferruginous,  with  concretions 

of  limestone  and  chert  -  -  70  feet. 

2.  Sand  with  green  matter   -  -  70  to  100  feet. 

3.  Calcareous  stone,  called  Kentish  rag         -  -  60  to  80  feet. 

In  his  detailed  description  of  the  fine  section  displayed  at  Ather- 
field,  in  the  south  of  the  Isle  of  Wight,  we  find  the  limestone  wholly 
wanting ;  in  fact,  the  variations  in  the  mineral  composition  of  this 
group,  even  in  contiguous  districts,  is  very  great ;  and  on  comparing 
the  Atherfield  beds  with  corresponding  strata  at  Hythe  in  Kent, 
distant  95  miles,  the  whole  series  presents  a  most  dissimilar  aspect.* 

On  the  other  hand,  Professor  E.  Forbes  has  shown  that  when  the 
sixty-three  strata  at  Atherfield  are  severally  examined,  the  total 
thickness  of  which  he  gives  as  843  feet,  there  are  some  fossils  which 
range  through  the  whole  series,  others  which  are  peculiar  to  parti- 
cular divisions.  As  a  proof  that  all  belong  chronologically  to  one 
system,  he  states  that  whenever  similar  conditions  are  repeated  in 
overlying  strata  the  same  species  reappear.  Changes  of  depth,  or  of 
the  mineral  nature  of  the  sea-bottom,  the  presence  or  absence  of  lime 
or  of  peroxide  of  iron,  the  occurrence  of  a  muddy,  or  a  sandy,  or  a 
gravelly  bottom,  are  marked  by  the  banishment  of  certain  species 
and  the  predominance  of  others.  But  these  differences  of  conditions 
being  mineral,  chemical,  and  local  in  their  nature,  have  nothing  to 
do  with  the  extinction,  throughout  a  large  area,  of  certain  animals  or 
plants.  The  rule  laid  down  by  this  eminent  naturalist  for  enabling 
us  to  test  the  arrival  of  a  new  state  of  things  in  the  animate  world, 
is  the  representation  by  new  and  different  species  of  corresponding 
genera  of  mollusca  or  other  beings.  When  the  forms  proper  to 
loose  sand  or  soft  clay,  or  a  stony  or  calcareous  bottom,  or  a  moderate 
or  a  great  depth  of  water,  recur  with  all  the  same  species,  the 
interval  of  time  has  been,  geologically  speaking,  small,  however 
dense  the  mass  of  matter  accumulated.  But  if,  the  genera  remaining 
the  same,  the  species  are  changed,  we  have  entered  upon  a  new 
period ;  and  no  similarity  of  climate,  or  of  geographical  and  local 
conditions,  can  then  recall  the  old  species  which  a  long  series  of 
destructive  causes  in  the  animate  and  inanimate  world  has  gradually 
annihilated.  On  passing  from  the  Lower  Greensand  to  the  Gault, 
we  suddenly  reach  one  of  these  new  epochs,  scarcely  any  of  the 
fossil  species  being  common  to  the  lower  and  upper  cretaceous 
systems,  a  break  in  the  chain  implying  no  doubt  many  missing  links 
in  the  series  of  geological  monuments,  which  we  may  some  day  be 
able  to  supply. 

One  of  the  largest  and  most  abundant  shells  in  the  lowest  strata 
of  the  Lower  Greensand,  as  displayed  in  the  Atherfield  section,  is 

*  Dr.  Fitton,  Quart.  Geol.  Journ.,  able  table  showing  the  vertical  range  of 
vol.  i.  p.  179.,  ii.  p.  55.,  and  iii.  p.  289.,  the  various  fossils  of  the  lower  green- 
where  comparative  sections  and  a  valu-  sand  at  Atherfield  are  given. 


CH.  XVIII.]  FOSSILS   OF   LOWER   GREENSAND.  259 

the  large  Perna  Mulleti,  of  which  a  reduced  figure  is  here  given 
(fig.  296.). 

Fig.  29G. 


Perna  Mulleti.    Desh.  in  Leym. 
a.  Exterior.  b.  Part  of  hinge  of  upper  valve. 

In  the  south  of  England,  during  the  accumulation  of  the  Lower 
Greensand  above  described,  the  bed  of  the  sea  appears  to  have  been 
continually  sinking,  from  the  commencement  of  the  period,  when  the 
freshwater  Wealden  beds  were  submerged,  to  the  deposition  of  those 
strata  on  which  the  gault  immediately  reposes. 

Pebbles  of  quartzose  sandstone,  jasper,  and  flinty  slate,  together 
with  grains  of  chlorite  and  mica,  speak  plainly  of  the  nature  of  the 
pre-existing  rocks,  from  the  wearing  down  of  which  the  Greensand 
beds  were  derived.  The  land,  consisting  of  such  rocks,  was  doubt- 
less submerged  before  the  origin  of  the  white  chalk,  a  deposit  which 
originated  in  a  more  open  sea,  and  in  clearer  waters. 

The  fossils  of  the  Lower  Cretaceous  are  for  the  most  part  speci- 
fically distinct  from  those  of  the  Upper  Cretaceous  strata. 

Among  the  former  we  often  meet  with  the  genus  Scaphites  (fig.  297.) 


Fig.  297. 


Fig.  298. 


Scaphites  gigas,  Sow. 


Syn.  Ancylocer as  gigas,  D'Orb. 
8  2 


Nautilus  plicatns,  Sow.,  in 
Fitton's  Monog. 


260 


WEALDEN   FORMATION. 


[CH.  XVIII. 


or  Ancyloceras,  which  has  been  aptly  described  as  an  ammonite  more 
or  less  uncoiled ;  also  a  furrowed  Nautilus,  N.  plicatus  (fig.  298.),  Tri- 
gonia  caudata,  likewise  found  in  the  Blackdown  beds  (see  above, 
p.  252.),  and  Gervillia,  a  bivalve  genus  allied  to  Avicula. 


Fig.  299. 


Fig.  300. 


Fig.  301. 


Trigonia  caudata,  Agass. 


Gervillia  anceps,  Desh. 


Terebratula  tella,  Sow 


WEALDEN  FORMATION. 

Beneath  the  Lower  Greensand  in  the  S.  E.  of  England,  a  fresh- 
water formation  is  found,  called  the  Wealden  (see  Nos.  5  and  6.  Map, 
fig.  320.  p.  273.),  which,  although  it  occupies  a  small  horizontal  area 
in  Europe,  as  compared  to  the  White  Chalk  and  Greensand,  is  never- 
theless of  great  geological  interest,  since  the  imbedded  remains  give 
us  some  insight  into  the  nature  of  the  terrestrial  fauna  and  flora 
of  the  Lower  Cretaceous  epoch.  The  name  of  Wealden  was  given 
to  this  group  because  it  was  first  studied  in  parts  of  Kent,  Surrey, 
and  Sussex,  called  the  Weald  (see  Map,  p.  273.);  and  we  are 
indebted  to  Dr.  Mantell  for  having  shown,  in  1822,  in  his  Geology  of 
Sussex,  that  the  whole  group  was  of  fluviatile  origin.  In  proof  of 
this  he  called  attention  to  the  entire  absence  of  Ammonites,  Belem- 
nites,  Terebratulae,  Echinites,  Corals,  and  other  marine  fossils,  so 
characteristic  of  the  cretaceous  rocks  above,  and  of  the  Oolitic  strata 
below,  and  to  the  presence  in  the  Weald  of  Paludinae,  Melanise,  and 
various  fluviatile  shells,  as  well  as  the  bones  of  terrestrial  reptiles  and 
the  trunks  and  leaves  of  land  plants. 

The  evidence  of  so  unexpected  a  fact  as  the  infra-position  of  a 
dense  mass  of  purely  freshwater  origin  to  a  deep-sea  deposit  (a  phe- 
nomenon with  which  we  have  since  become  familiar)  was  received, 
at  first,  with  no  small  doubt  and  incredulity.  But  the  relative  po- 
sition of  the  beds  is  unequivocal ;  the  Weald  Clay  being  distinctly 
seen  to  pass  beneath  the  Lower  Greensand  in  various  parts  of  Surrey, 
Kent,  and  Sussex,  and  to  re-appear  in  the  Isle  of  Wight  at  the  base 
of  the  Cretaceous  Series,  being,  no  doubt,  continuous  far  beneath  the 
surface,  as  indicated  by  the  dotted  lines  in  the  annexed  diagram, 
fig.  302. 

Fig.  302. 
Isle  of  Wight. 


Hants. 


Sussex. 


a.  Chalk.       ft.  Greensand.       c.  Weald  Clay.       d,  Hastings  Sand.       e.  Purbeck  beds. 


CH.  XVIII.]  WEALD   CLAY.  261 

The  Wealden  is  divisible  into  two  minor  groups :  — 

Thickness. 
1st.  Weald  Clay,  chiefly  argillaceous,  but  sometimes  including 

thin  beds  of  sand  and  shelly  limestone  with  Paludina       140  to    280  ft. 
2d.   Hastings  Sand,  chiefly  arenaceous,  but  in  which  occur 

some  clays  and  calcareous  grits*         -  -    400  to  1000  ft. 

Another  freshwater  formation,  called  the  Purbeck,  consisting  of 
various  limestones  and  marls,  containing  distinct  species  of  molluscs, 
Cyprides,  and  other  fossils,  lies  immediately  beneath  the  Wealden  in 
the  south-east  of  England.  As  it  is  now  found  to  be  more  nearly 
related,  by  its  organic  remains,  to  the  Oolitic  than  to  the  Cretaceous 
Series,  it  will  be  treated  of  in  the  20th  Chapter. 

Weald  Clay. 

The  upper  division,  or  Weald  Clay,  is  of  purely  freshwater  origin. 
Its  highest  beds  are  not  only  conformable,  as  Dr.  Fitton  observes,  to 
the  inferior  strata  of  the  Lower  G-reensand,  but  of  similar  mineral 
composition.  To  explain  this,  we  may  suppose,  that,  as  the  delta  of 
a  great  river  was  tranquilly  subsiding,  so  as  to  allow  the  sea  to  en- 
croach upon  the  space  previously  occupied  by  fresh  water,  the  river 
still  continued  to  carry  down  the  same  sediment  into  the  sea.  In 
confirmation  of  this  view  it  may  be  stated,  that  the  remains  of  the 
Iguanodon  Mantelli,  a  gigantic  terrestrial  reptile,  very  characteristic 
of  the  Wealden,  has  been  discovered  near  Maidstone,  in  the  overlying 
Kentish  rag,  or  marine  limestone  of  the  Lower  Greensand.  Hence 
we  may  infer,  that  some  of  the  saurians  which  inhabited  the  country 
of  the  great  river  continued  to  live  when  part  of  the  country  had 
become  submerged  beneath  the  sea.  Thus,  in  our  own  times,  we 
may  suppose  the  bones  of  large  alligators  to  be  frequently  entombed 
in  recent  freshwater  strata  in  the  delta  of  the  Ganges.  But  if  part 
of  that  delta  should  sink  down  so  as  to  be  covered  by  the  sea,  marine 
formations  might  begin  to  accumulate  in  the  same  space  where  fresh- 
water beds  had  previously  been  formed  ;  and  yet  the  Ganges  might 
still  pour  down  its  turbid  waters  in  the  same  direction,  and  carry 
seaward  the  carcases  of  the  same  species  of  alligator,  in  which  case 
their  bones  might  be  included  in  marine  as  well  as  in  subjacent  fresh- 
water strata. 

The  Iguanodon,  first  discovered  by  Dr.  Mantell,  has  left  more  of 
its  remains  in  the  Wealden  strata  of  the  south-eastern  counties  and 
Isle  of  Wight  than  has  any  other  genus  of  associated  saurians.  It 
was  an  herbivorous  reptile,  and  regarded  by  Cuvier  as  more  extra- 
ordinary than  any  with  which  he  was  acquainted ;  for  the  teeth, 
though  bearing  a  great  analogy,  in  their  general  form  and  crenated 
edges  (see  figs.  303.  a.,  303.  £.),  to  the  modern  Iguanas  which  now 
frequent  the  tropical  woods  of  America  and  the  West  Indies,  ex- 
hibit many  striking  and  important  differences.  It  appears  that  they 
liave  often  been  worn  by  the  process  of  mastication ;  whereas  the 

*  Dr.  Fitton,  Geol.  Trans.  Second  Series,  vol.  iv.  p.  320. 
s  3 


262 


FOSSILS   OP    THE 


[On.  XVIII. 


existing  herbivorous  reptiles  clip  and  gnaw  off  the  vegetable  pro- 
ductions on  which  they  feed,  but  do  not  chew  them.  Their  teeth 
frequently  present  an  appearance  of  having  been  chipped  off,  but 
never,  like  the  fossil  teeth  of  the  Iguanodon,  have  a  flat  ground 
surface  (see  fig.  304.  #.),  resembling  the  grinders  of  herbivorous 

Fig.  303.  Fig.  304. 


Fig.  303.  /T,  b.  Tooth  of  Iguanodon  Mantetti. 
Fig.  304.  a.  Partially  worn  tooth  of  young  individual  of  the  same. 
b.  Crown  of  tooth  in  adult,  worn  down.    (Mantell.) 

mammalia.  Dr.  Mantell  computes  that  the  teeth  and  bones  of  this 
species  which  passed  under  his  examination  during  twenty  years 
must  have  belonged  to  no  less  than  seventy-one  distinct  individuals, 
varying  in  age  and  magnitude  from  the  reptile  just  burst  from  the 
«gg,  to  one  of  which  the  femur  measured  24  inches  in  circum- 
ference. Yet,  notwithstanding  that  the  teeth  were  more  numerous 
than  any  other  bones,  it  is  remarkable  that  it  was  not  until  the  relics 
of  all  these  individuals  had  been  found,  that  a  solitary  example  of 
part  of  a  jaw-bone  was  obtained.  More  recently  remains  both  of  the 
upper  and  lower  jaw  have  been  met  with  in  the  Hastings  Beds  in 
Tilgate  Forest.  Their  size  was  somewhat  greater  than  had  been 
anticipated,  and  Dr.  Mantell,  who  does  not  agree  with  Professor 
Owen  that  the  tail  was  short,  estimates  the  probable  length  of  some 
of  these  saurians  at  between  50  and  60  feet.  The  largest  femur  yet 
found  measures  4  feet  8  inches  in  length,  the  circumference  of  the 
shaft  being  25  inches,  and,  if  measured  round  the  condyles,  42  inches. 

Occasionally  bands  of  limestone,  called  Sussex  Marble,  occur  in 
the  Weald  Clay,  almost  entirely  composed  of  a  species  of  Paludina, 
closely  resembling  the  common  P.  vivipara  of  English  rivers. 

Shells  of  the  Cypris,  a  genus  of  Crustaceans  before  mentioned 
(p.  31.)  as  abounding  in  lakes  and  ponds,  are  also  plentifully  scat- 
tered through  the  clays  of  the  Wealden,  sometimes  producing,  like 
plates  of  mica,  a  thin  lamination  (see  fig.  307.).  Similar  cypris- 
bearing  marls  are  found  in  the  lacustrine  tertiary  beds  of  Auvergne 
(see  above,  p.  200.). 


CH.  XVIII.] 

Fig.  305. 


WEALDEN   GROUP. 

Fig.  306. 


263 


Cypris  Valdensis,  Fitton. 
(C.Jaba,  Min.  Con.  485.) 


Weald  clay  with  Cyprides. 


Hastings  Sands. 

This  lower  division  of  the  Wealden  consists  of  sand,  calciferous 
grit,  clay,  and  shale ;  the  argillaceous  strata,  notwithstanding  the 
name,  being  nearly  in  the  same  proportion  as  the  arenaceous.  The 
calcareous  sandstone  and  grit  of  Tilgate  Forest,  near  Cuckfield,  in 
which  the  remains  of  the  Iguanodon  and  Hylasosaurus  were  first 
found,  constitute  an  upper  member  of  this  formation.  The  white 
"  sand-rock  "  of  the  Hastings  cliffs,  about  100  feet  thick,  is  one  of 
the  lower  members  of  the  same.  The  reptiles,  which  are  very  abun- 
dant in  this  division,  consist  partly  of  saurians,  already  referred  by 
Owen  and  Mantell  to  eight  genera,  among  which,  besides  those 
already  enumerated,  we  find  the  Megalosaurus  and  Plesiosaurus. 
The  Pterodactyl  also,  a  flying  reptile,  is  met  with  in  the  same  strata, 
and  many  remains  of  Chelonians  of  the  genera  Trioynx  and  Emys, 
now  confined  to  tropical  regions. 

The  fishes  of  the  Wealden  are  chiefly  referable  to  the  Ganoid  and 
Placoid  orders.  Among  them  the  teeth  and  scales  of  Lepidotus  are 
most  widely  diffused  (see  fig.  308.).  These  ganoids  were  allied  to 

Fig.  308. 


Lepidotus  Mantelli,  Agass.     Wealden. 
a.  palate  and  teeth.  b.  side  view  of  teeth. 


c.  scale. 


the  Lepidosteus,  or  Gar-pike,  of  the  American  rivers.  The  whole 
body  was  covered  with  large  rhomboidal  scales,  very  thick,  and 
having  the  exposed  part  coated  with  enamel.  Most  of  the  species  of 
this  genus  are  supposed  to  have  been  either  river-fish,  or  inhabitants 
of  the  sea  at  the  mouth  of  estuaries. 

The  shells  of  the  Hastings  beds  belong  to  the  genera  Melanopsis, 
Melania,  Paludina,  Cyrena,  Cyclas,  Unio  (see  fig.  309.),  and  others, 
which  inhabit  rivers  or  lakes ;  but  one  band  has  been  found  at 
Punfield,  in  Dorsetshire,  indicating  a  brackish  state  of  the  water, 
where  the  genera  Corbula  (see  fig.  310.),  Mytilus,  and  Ostrea  occur ; 

B  4 


264 


WEALDEN   FOSSILS. 


[Cn.  XVIII. 


Fig 


Fig.  310. 


Corbnla  alata,  Fitton.     Magnified. 
In  brackish-water  beds  of  the  Hastings 
Sands,  Punfield  Bay. 


Unio  Valdensis,  Mant. 

Isle  of  Wight  and  Dorsetshire ;  in  the  lower  beds 
of  the  Hastings  Sands. 

and  in  some  places  this  bed  becomes  purely  marine,  the  species 
being  for  the  most  part  peculiar,  but  several  of  them  well-known 
Lower  Greensand  fossils,  among  which  Ammonites  Deshayesii  may 
be  mentioned.  These  facts  show  how  closely  related  were  the  faunas 
of  the  Wealden  and  Cretaceous  periods. 

At  different  heights  in  the  Hastings  Sand,  we  find  again  and 
again  slabs  of  sandstone  with  a  strong  ripple-mark,  and  between 
these  slabs  beds  of  clay  many  yards  thick.  In  some  places,  as  at 
Stammerham,  near  Horsham,  there  are  indications  of  this  clay 
having  been  exposed  so  as  to  dry  and  crack  before  the  next  layer 
was  thrown  down  upon  it.  The  open  cracks  in  the  clay  have 
served  as  moulds,  of  which  casts  have  been  taken  in  relief,  and 
which  are,  therefore,  seen  on  the  lower  surface  of  the  sandstone 
(see  fig.  311.). 

Fig.  311. 


Underside  of  slab  of  sandstone  about  one  yard  in  diameter. 
Stammerham,  Sussex. 

Near  the  same  place  a  reddish  sandstone  occurs  in  which  are 
innumerable  traces  of  a  fossil  vegetable,  apparently  Sphenopteris,  the 
stems  and  branches  of  which  are  disposed  as  if  the  plants  were 
standing  erect  on  the  spot  where  they  originally  grew,  the  sand 
having  been  gently  deposited  upon  and  around  them ;  and  similar 


CH.  XVIII.] 


AREA   OP    THE   WEALDEN. 


265 


gradifs  (Fitton),  from  the 

Hastings  Sands  near  Tunbridge  Wells. 
a.  a  portion  of  the  same  magnified. 


appearances   have   been   remarked  in  other  places   in  this  forma- 
Fig.3i2.  tion.*     In  the  same   division  also  of 

the  Wealden,  at  Cuckfield,  is  a  bed 
of  gravel  or  conglomerate,  consisting 
of  water-worn  pebbles  of  quartz  and 
jasper,  with  rolled  bones  of  reptiles. 
These  must  have  been  drifted  by  a 
current,  probably  in  water  of  no  great 
depth. 

From  such  facts  we  may  infer  that, 
notwithstanding  the  great  thickness  of 

.  .      ,.    .    .  „    .       TSr      ,,  ,  ,     .. 

thlf  <*!VlSlOn  of  the  Wealden,  the  whole 

of  it  was  a  deposit  in  water  of  a  mo- 
derate depth,  and  often  extremely  shallow.  This  idea  may  seem 
startling  at  first,  yet  such  would  be  the  natural  consequence  of  a 
gradual  and  continuous  sinking  of  the  ground  in  an  estuary  or 
bay,  into  which  a  great  river  discharged  its  turbid  waters.  By 
each  foot  of  subsidence,  the  fundamental  rock  would  be  depressed 
one  foot  farther  from  the  surface  ;  but  the  bay  would  not  be  deep- 
ened, if  newly  deposited  mud  and  sand  should  raise  the  bottom 
one  foot.  On  the  contrary,  such  new  strata  of  sand  and  mud 
might  be  frequently  laid  dry  at  low  water,  or  overgrown  for  a 
season  by  a  vegetation  proper  to  marshes. 

Area  of  the  Wealden.  —  In  regard  to  the  geographical  extent 
of  the  Wealden,  it  cannot  be  accurately  laid  down;  because  so 
much  of  it  is  concealed  beneath  the  newer  marine  formations.  It 
has  been  traced  about  200  English  miles  from  west  to  east,  from 
the  coast  of  Dorsetshire  to  near  Boulogne,  in  France  ;  and  nearly 
200  miles  from  north-west  to  south-east,  from  Surrey  and  Hamp- 
shire to  Beauvais,  in  France.  If  the  formation  be  continuous 
throughout  this  space,  which  is  very  doubtful,  it  does  not  follow 
that  the  whole  was  contemporaneous;  because,  in  all  likelihood, 
the  physical  geography  of  the  region  underwent  frequent  changes 
throughout  the  whole  period,  and  the  estuary  may  have  altered 
its  form,  and  even  shifted  its  place.  Dr.  Dunker,  of  Cassel,  and 
H.  Von  Meyer,  in  an  excellent  monograph  on  the  Wealdens  of 
Hanover  and  Westphalia,  have  shown  that  they  correspond  so 
closely,  not  only  in  their  fossils,  but  also  in  their  mineral  characters, 
with  the  English  series,  that  we  can  scarcely  hesitate  to  refer  the 
whole  to  one  great  delta.  Even  then,  the  magnitude  of  the  deposit 
may  not  exceed  that  of  many  modern  rivers.  Thus,  the  delta  of  the 
Quorra  or  Niger,  in  Africa,  stretches  into  the  interior  for  more  than 
170  miles,  and  occupies,  it  is  supposed,  a  space  of  more  than  300 
miles  along  the  coast,  thus  forming  a  surface  of  more  than  25,000 
square  miles,  or  equal  to  about  one  half  of  England.f  Besides,  we 
know  not,  in  such  cases,  how  far  the  fluviatile  sediment  and  organic 


*  Mantell,  GeoL  of  S.  E.  of  England, 
p.  244. 


f  Fitton,  Geol.  of  Hastings,  p.  58.; 
who  cites  Lander's  Travels. 


266  LOWER   CRETACEOUS   AND  [Cn.  XVIII. 

remains  of  the  river  and  the  land  may  be  carried  out  from  the  coast, 
and  spread  over  the  bed  of  the  sea.  I  have  shown,  when  treating  of 
the  Mississippi,  that  a  more  ancient  delta,  including  species  of  shells, 
such  as  now  inhabit  Louisiana,  has  been  upraised,  and  made  to  oc- 
cupy a  wide  geographical  area,  while  a  newer  delta  is  forming  * ;  and 
the  possibility  of  such  movements,  and  their  effects,  must  not  be  lost 
sight  of  when  we  speculate  on  the  origin  of  the  Wealden. 

If  it  be  asked  where  the  continent  was  placed  from  the  ruins  of 
which  the  Wealden  strata  were  derived,  and  by  the  drainage  of  which 
a  great  river  was  fed,  we  are  half  tempted  to  speculate  on  the  former 
existence  of  the  Atlantis  of  Plato.  The  story  of  the  submergence  of 
an  ancient  continent,  however  fabulous  in  history,  must  have  been 
true  again  and  again  as  a  geological  event. 

The  real  difficulty  consists  in  the  persistence  of  a  large  hydro- 
graphical  basin,  from  whence  a  great  body  of  fresh  water  was  poured 
into  the  sea,  precisely  at  a  period  when  the  neighbouring  area  of  the 
Wealden  was  gradually  going  downwards  1000  feet  or  more  perpen- 
dicularly. If  the  adjoining  land  participated  in  the  movement,  how 
could  it  escape  being  submerged,  or  how  could  it  retain  its  size  and 
altitude  so  as  to  continue  to  be  the  source  of  such  an  inexhaustible 
supply  of  fresh  water  and  sediment  ?  In  answer  to  this  question, 
we  are  fairly  entitled  to  suggest  that  the  neighbouring  land  may 
have  been  stationary,  or  may  even  have  undergone  a  contempora- 
neous slow  upheaval.  There  may  have  been  an  ascending  move- 
ment in  one  region,  and  a  descending  one  in  a  contiguous  parallel 
zone  of  country ;  just  as  the  northern  part  of  Scandinavia  is  now 
rising,  while  the  middle  portion  (that  south  of  Stockholm)  is  un- 
moved, and  the  southern  extremity  in  Scania  is  sinking,  or  at 
least  has  sunk  within  the  historical  period,  f  We  must,  nevertheless, 
conclude,  if  we  adopt  the  above  hypothesis,  that  the  depression  of 
the  land  became  general  throughout  a  large  part  of  Europe  at  the 
close  of  the  Wealden  period,  and  this  subsidence  brought  in  the  cre- 
taceous ocean. 


FLORA  OF   THE   LOWER   CRETACEOUS   AND   WEALDEN   PERIOD. 

The  terrestrial  plants  of  the  Upper  Cretaceous  epoch  are  but 
little  known,  as  might  be  expected,  since  the  rocks  are  of  purely 
marine  origin,  formed  for  the  most  part  far  from  land.  But  the 
Lower  Cretaceous  or  Neocomian  vegetation,  including  that  of  the 
Weald  Clay  and  Hastings  Sands,  is  by  no  means  scanty.  M.  Adolphe 
Brongniart,  when  dividing  the  whole  fossiliferous  series  into  three 
groups  in  reference  solely  to  fossil  plants,  has  named  the  primary 
strata  "  the  age  of  acrogens ; "  the  secondary,  exclusive  of  the 
cretaceous,  "  the  age  of  gymnogens ; "  and  the  third,  comprising 

*  See  above,  p.  84.;  and  Second  Visit  Geol.  Soc.  1850,  Quart.  Geol.  Journ. 
to  the  TJ.  S.  vol.  ii.  chap,  xxxiv.  vol.  vi.  p.  52. 

f  See  the  Author's  Annivers.  Address, 


CH.  XVIII. ]  WEALDEN   FLORA.  267 

the  cretaceous  and  tertiary,  "the  age  of  angiosperms."*  He  con- 
siders the  lower  cretaceous  flora  as  displaying  a  transitional  cha- 
racter from  that  of  a  secondary  to  that  of  a  tertiary  vegetation. 
Coniferce  and  Cycadece  (or  Gymnogens)  still  flourished,  as  in  the 
preceding  oolitic  and  triassic  epochs ;  but,  together  with  these,  some 
well-marked  leaves  of  dicotyledonous  trees,  of  a  genus  named 
Credneria,  have  long  been  known.  They  are  met  with  in  the 
"quader-sandstein"  and  "  planer -kalk"  of  Germany,  rocks  of  the  Upper 
Cretaceous  group.  More  recently,  Dr.  Deby  has  discovered  in  the 
Lower  Cretaceous  beds  of  Aix-la-Chapelle  a  great  variety  of  dicoty- 
ledonous leaves  |,  belonging  to  no  less,  according  to  his  enumeration, 
than  26  species,  some  of  the  leaves  being  from  four  to  six  inches  in 
length,  and  in  a  beautiful  state  of  preservation.  In  the  absence  ol 
the  organs  of  fructification  and  of  fossil  fruits,  the  number  of  species 
may  be  exaggerated;  but  we  may  certainly  affirm,  reasoning  from 
our  present  data,  that  when  the  lower  chalk  of  Aix-la-Chapelle 
originated,  Dicotyledonous  Angiosperms  flourished  in  that  region  in 
equal  proportions  with  Gymnosperms.  This  discovery  has  an  im- 
portant bearing  on  some  popular  theories,  for  until  lately  none  of 
these  Exogens  (a  class  now  constituting  three  fourths  of  the  living 
plants  of  the  globe)  had  been  detected  in  any  strata  older  than  the 
Eocene.  Moreover,  some  geologists  have  wished  to  connect  the 
rarity  of  dicotyledonous  trees  with  a  peculiarity  in  the  state  of  the 
atmosphere  in  the  earlier  ages  of  the  planet,  imagining  that  a  denser 
air  and  noxious  gases,  especially  carbonic  acid  gas  being  in  excess, 
were  adverse  to  the  prevalence,  not  only  of  the  quick-breathing 
classes  of  animals  (mammalia  and  birds),  but  to  a  flora  like  that  now 
existing,  while  it  favoured  the  predominance  of  reptile  life,  and  a 
cryptogamic  and  gymnospermous  flora.  The  co-existence,  therefore, 
of  Dicotyledonous  Angiosperms  in  abundance  with  Cycads  and  Co- 
niferae,  and  with  a  rich  reptilian  fauna,  comprising  the  Iguanodon, 
Megalosaurus,  Hylaeosaurus,  Ichthyosaurus,  Plesiosaurus,  and  Ptero- 

*  In  this  and  subsequent  remarks  on  fossil  plants  I  shall  often  use  Dr.  Lindley's 
terms,  as  most  familiar  in  this  country ;  but  as  those  of  M.  A.  Brongniart  are 
much  cited,  it  may  be  useful  to  geologists  to  give  a  table  explaining  the  corre- 
sponding names  of  groups  so  much  spoken  of  in  palaeontology. 

Brongniart.  Lindley. 

1.  Cryptogamous    am- "I 

phigens,  or  cellular  >     Thallogens.        Lichens,  sea-weeds,  fungi, 
cryptogamic. 

2.  Cryptogamous  aero-        Acrogens.          Mosses,  equisetums,  ferns,  lyco- 

gens.  podiums, — Lepidodendron. 

3.  Dicotyledonous  gym-        Gymnogens.      Conifers  and  Cycads. 

nosperms. 

4.  Dicot.  Angiosperms.         Exogens.  Composite,  leguminosae,  umbelli- 

ferae,  cruciferae,  heaths,  &c.  All 
native  European  trees  except 
conifers. 

5.  Monocotyledons.  Endogens.          Palms,  lilies,  aloes,  rushes,  grasses, 

&c. 
f  Geol.  Quart.  Jour.  vol.  vii.  part  2.  Miscell.  p.  111. 


268  INLAND   CHALK-CLIFFS  [Cn.  XIX. 

dactyl,  in  the  Lower  Cretaceous  series,  tends  manifestly  to  dispel  the 
idea  of  a  meteorological  state  of  things  in  the  secondary  periods 
so  widely  distinct  from  that  now  prevailing. 

Among  the  recent  additions  made  to  the  fossil  flora  of  the  Weal- 
den,  and  one  which  supplies  a  new  link  between  it  and  the  tertiary 
flora,  I  may  mention  the  Gyrogonites,  or  spore-vessels  of  the  Chara, 
lately  found  in  the  Hastings  series  of  the  Isle  of  Wight. 


CHAPTER  XIX. 

DENUDATION  OF  THE  CHALK  AND  WEALDEN. 

Physical  geography  of  certain  districts  composed  of  Cretaceous  and  Wealden  strata 
— Lines  of  inland  chalk-cliffs  on  the  Seine  in  Normandy — Outstanding  pillars 
and  needles  of  chalk — Denudation  of  the  chalk  and  Wealden  in  Surrey,  Kent, 
and  Sussex — Chalk  once  continuous  from  the  North  to  the  South  Downs  — 
Anticlinal  axis  and  parallel  ridges — Longitudinal  and  transverse  valleys  — 
Chalk  escarpments — Kiseand  denudation  of  the  strata  gradual — Ridges  formed 
by  harder,  valleys  by  softer  beds — At  what  periods  the  Weald  Valley  was 
denuded — Why  no  alluvium,  or  wreck  of  the  chalk,  in  the  central  district  of  the 
Weald — Land  has  most  prevailed  where  denudation  has  been  greatest  — 
Elephant  bed,  Brighton — Sangatte  Cliff — Conclusion. 

ALL  the  fossiliferous  formations  may  be  studied  by  the  geologist  in 
two  distinct  points  of  view :  first,  in  reference  to  their  position  in 
the  series,  their  mineral  character  and  fossils ;  and,  secondly,  in 
regard  to  their  physical  geography,  or  the  manner  in  which  they  now 
enter,  as  mineral  masses,  into  the  external  structure  of  the  earth ; 
forming  the  bed  of  lakes  and  seas,  or  the  surface  or  foundation  of 
hills  and  valleys,  plains  and  table-lands.  Some  account  has  already 
been  given,  on  the  first  head,  of  the  Tertiary,  the  Cretaceous,  and 
the  Wealden  strata ;  and  we  may  now  proceed  to  consider  certain 
features  in  the  physical  geography  of  these  groups  as  they  occur  in 
parts  of  England  and  France. 

The  hills  composed  of  white  chalk  in  the  S.  E.  of  England  have  a 
smooth  rounded  outline,  and,  being  usually  in  the  state  of  sheep- 
pastures,  are  free  from  trees  or  hedgerows;  so  that  we  have  an 
opportunity  of  observing  how  the  valleys  by  which  they  are  drained 
ramify  in  all  directions,  and  become  wider  and  deeper  as  they  descend. 
Although  these  valleys  are  now  for  the  most  part  dry,  except  during 
heavy  rains  and  the  melting  of  snow,  they  may  have  been  due  to 
aqueous  denudation,  as  explained  in  the  sixth  chapter  ;  having  been 
excavated  when  the  chalk  emerged  gradually  from  the  sea.  This 
opinion  is  confirmed  by  the  occasional  occurrence  of  what  appear  to 
be  long  lines  of  inland  cliffs,  in  which  the  strata  are  cut  off  abruptly 
in  steep  and  often  vertical  precipices.  The  true  nature  of  such 
escarpments  is  nowhere  more  obvious  than  in  parts  of  Normandy, 


CH.  XIX.]  IN   NOKMANDT.  269 

where  the  river  Seine  and  its  tributaries  flow  through  deep  winding 
valleys,  hollowed  out  of  chalk  horizontally  stratified.  Thus,  for 
example,  if  we  follow  the  Seine  for  a  distance  of  about  30  miles 
from  Andelys  to  Elbosuf,  we  find  the  valley  flanked  on  both  sides 
by  a  steep  slope  of  chalk,  with  numerous  beds  of  flint,  the  formation 
being  laid  open  for  a  thickness  of  about  250  and  300  feet.  Above 
the  chalk  is  an  overlying  mass  of  sand,  gravel,  and  clay,  from  30  to 
100  feet  thick.  The  two  opposite  slopes  of  the  hills  a  and  b,  fig.  313., 

Fig.  313. 


Section  across  Valley  of  Seine. 

where  the  chalk  appears  at  the  surface,  are  from  2  to  4  miles  apart, 
and  they  are  often  perfectly  smooth  and  even,  like  the  steepest  of 
our  downs  in  England  ;  but  at  many  points  they  are  broken  by  one, 
two,  or  more  ranges  of  vertical  and  even  overhanging  cliffs  of  bare 
white  chalk  with  flints.  At  some  points  detached  needles  and  pin- 
nacles stand  in  the  line  of  the  cliffs,  or  in  front  of  them,  as  at  c,  fig. 
313.  On  the  right  bank  of  the  Seine,  at  Andelys,  one  range,  about 
2  miles  long,  is  seen  varying  from  50  to  100  feet  in  perpendicular 
height,  and  having  its  continuity  broken  by  a  number  of  dry  valleys 
or  coombs,  in  one  of  which  occurs  a  detached  rock  or  needle,  called 
the  Tete  d'Homme  (see  figs.  314,  315.).  The  iop  of  this  rock  pre- 

Fig.  314. 


View  of  the  Tete  d'Homme,  Andelys,  seen  from  above. 


sents  a  precipitous  face  towards  every  point  of  the  compass ;  its 
vertical  height  being  more  than  20  feet  on  the  side  of  the  downs, 
and  40  towards  the  Seine,  the  average  diameter  of  the  pillar  being 
36  feet.  Its  composition  is  the  same  as  that  of  the  larger  cliffs  in 


270 


INLAND   CLIFFS   AND    NEEDLES  [Cn.  XIX. 

Fig.  315. 


Side  view  of  the  Tele  d'Homme.    White  chalk  with  flints. 

its  neighbourhood,  namely,  white  chalk,  having  occasionally  a  crys- 
talline texture  like  marble,  with  layers  of  flint  in  nodules  and  tabular 
masses.  The  flinty  beds  often  project  in  relief  4  or  5  feet  beyond 
the  white  chalk,  which  is  generally  in  a  state  of  slow  decomposition, 
either  exfoliating  or  being  covered  with  white  powder,  like  the 
chalk  cliffs  on  the  English  coast ;  and,  as  in  them,  this  superficial 
powder  contains  in  some  places  common  salt. 

Other  cliffs  are  situated  on  the  right  bank  of  the  Seine,  opposite 
Tournedos,  between  Andelys  and  Pont  de  1'Arche,  where  the  preci- 
pices are  from  50  to  80  feet  high :  several  of  their  summits  terminate 
in  pinnacles  ;  and  one  of  them,  in  particular,  is  so  completely  de- 
tached as  to  present  a  perpendicular  face  50  feet  high  towards  the 
sloping  down.  On  these  cliffs  several  ledges  are  seen,  which  mark 
so  many  levels  at  which  the  wares  of  the  sea  may  be  supposed  to  have 
encroached  for  a  long  period.  At  a  still  greater  height,  immediately 
above  the  top  of  this  range,  are  three  much  smaller  cliffs,  each  about 
4  feet  high,  with  as  many  intervening  terraces,  which  are  continued 
so  as  to  sweep  in  a  semicircular  form  round  an  adjoining  coomb,  like 
those  in  Sicily  before  described  (p.  76.). 

If  we  then  descend  the  river  from  Vatteville  to  a  place  called 
Senneville,  we  meet  with  a  singular  needle  about  50  feet  high,  per- 
fectly isolated  on  the  escarpment  of  chalk  on  the  right  bank  of  the 
Seine  (see  fig.  316.).  Another  conspicuous  range  of  inland  cliffs  is 
situated  about  12  miles  below  on  the  left  bank  of  the  Seine,  begin- 
ning at  Elbceuf,  and  comprehending  the  Roches  d'Orival  (see  fig.  317.). 
Like  those  before  described,  it  has  an  irregular  surface,  often  over- 
hanging, and  with  beds  of  flint  projecting  several  feet.  Like  them, 
also,  it  exhibits  a  white  powdery  surface,  and  consists  entirely  of 
horizontal  chalk  with  flints.  It  is  40  miles  inland  ;  its  height,  in 
some  parts,  exceeds  200  feet ;  and  its  base  is  only  a  few  feet  above 
the  level  of  the  Seine.  It  is  broken,  in  one  place,  by  a  pyramidal 
mass  or  needle,  200  feet  high,  called  the  Roche  de  Pignon,  which 
stands  out  about  25  feet  in  front  of  the  upper  portion  of  the  main  cliffs. 


CH.  XIX.]  OF   CHALK   IN   NORMANDY. 

Fig.  316.  Fig.  317. 


271 


Chalk  pinnacle  at  Senneville. 


Roches  d'Orival,  Elbceuf. 


with  which  it  is  united  by  a  narrow  ridge  about  40  feet  lower  than 
its  summit  (see  fig.  318.).   Like  the  detached  rocks  before  mentioned 


Fig.  318. 


View  of  the  Roche  de  Pignon,  seen  from  the  south. 

at  Senneville,  Vatteville,  and  Andelys,  it  may  be  compared  to  those 
needles  of  chalk  which  occur  on  the  coast  of  Normandy*  (see  fig. 
319.),  as  well  as  in  the  Isle  of  Wight  and  in  Purbeck. 

The  foregoing  description  and  drawings  will  show,  that  the 
evidence  of  certain  escarpments  of  the  chalk  having  been  originally 
sea-cliffs,  is  far  more  full  and  satisfactory  in  France  than  in  England. 
If  it  be  asked  why,  in  the  interior  of  our  own  country,  we  meet  with 
no  ranges  of  precipices  equally  vertical  and  overhanging,  and  no 
isolated  pillars  or  needles,  we  may  reply  that  the  greater  hardness  of 
the  chalk  in  Normandy  may,  no  doubt,  be  the  chief  cause  of  this 
difference.  But  the  frequent  absence  of  all  signs  of  littoral  denuda- 


*  An  account  of  these  cliffs  was  read  by  the  author  to  the  British  Assoc.  at 
Glasgow,  Sept.  1840. 


272 


DENUDATION   OF   THE 

Tig.  319. 


[Cn.  XIX, 


Needle  and  Arch  of  Etretat,  in  the  chalk  cliffs  of  Normandy. 
Height  of  Arch  100  feet.    (Passy.)* 

tion  in  the  valley  of  the  Seine  itself  is  a  negative  fact  of  a  far  more 
striking  and  perplexing  character.  The  cliffs,  after  being  almost 
continuous  for  miles,  are  then  wholly  wanting  for  much  greater  dis- 
tances, being  replaced  by  a  green  sloping  down,  although  the  beds 
remain  of  the  same  composition,  and  are  equally  horizontal ;  and 
although  we  may  feel  assured  that  the  manner  of  the  upheaval  of 
the  land,  whether  intermittent  or  not,  must  have  been  the  same  at 
those  intermediate  points  where  no  cliffs  exist,  as  at  others  where 
they  are  so  fully  developed.  But,  in  order  to  explain  such  apparent 
anomalies,  the  reader  must  refer  again  to  the  theory  of  denudation, 
as  expounded  in  the  6th  chapter ;  where  it  was  shown,  first,  that  the 
undermining  force  of  the  waves  and  marine  currents  varies  greatly 
at  different  parts  of  every  coast ;  secondly,  that  precipitous  rocks 
have  often  decomposed  and  crumbled  down ;  and  thirdly,  that  ter- 
races and  small  cliffs  may  occasionally  lie  concealed  beneath  a  talus 
of  detrital  matter. 

Denudation  of  the  Weald  Valley. — No  district  is  better  fitted  to 
illustrate  the  manner  in  which  a  great  series  of  strata  may  have  been 
upheaved  and  gradually  denuded  than  the  country  intervening  be- 
tween the  North  and  South  Downs.  This  region,  of  which  a  ground- 
plan  is  given  in  the  accompanying  map  (fig.  320.),  comprises  within 
it  the  whole  of  Sussex,  and  parts  of  the  counties  of  Kent,  Surrey, 
and  Hampshire.  The  space  in  which  the  formations  older  than  the 
White  Chalk,  or  those  from  the  Gault  to  the  Hastings  sands  inclu- 
sive, crop  out,  is  bounded  everywhere  by  a  great  escarpment  of 
chalk,  which  is  continued  on  the  opposite  side  of  the  channel  in  the 
Bas  Boulonnais  in  France,  where  it  forms  the  semicircular  boundary 
of  a  tract  in  which  older  strata  also  appear  at  the  surface.  The 
whole  of  this  district  may  therefore  be  considered  geologically  as 
one  and  the  same. 

The  space  here  inclosed  within  the  escarpment  of  the  chalk  affords 
an  example  of  what  has  been  sometimes  called  a  "  valley  of  eleva- 
tion" (more  properly  "of  denudation");  where  the  strata,  partially 
removed  by  aqueous  excavation,  dip  away  on  all  sides  from  a  central 
axis.  Thus,  it  is  supposed  that  the  area  now  occupied  by  the 

*  Seine-Inferieure,  p.  142.  and  pi.  6.  fig.  1. 


CH.  XIX.] 


CHALK   AND   WEALDEN. 

Fig.  320. 


273 


Jieachylleaa, 
ENGLISH  CHANNEL 


Geological  Map  of  the  south-east  of  England,  and  part  of  France,  exhibiting  the  denudation  of 

the  Weald. 

1.  IHim  Tertiary. 

2.  I        I  Chalk  and  Upper  Greensand. 

3.  —  Gault. 

4.  F^i  Lower  Greensand. 


5.  Weald  clay. 

6.  li-'-'--'----i  Hastings  sands. 

7.  Purbeck  beds. 

8.  Oolite. 


Hastings  sand  (No.  6.)  was  once  covered  by  the  Weald  clay  (No.  5.), 
and  this  again  by  the  Greensand  (No.  4.),  and  this  by  the  Gault 
(No.  3.);  and,  lastly,  that  the  Chalk  (No.  2.)  extended  originally 
over  the  whole  space  between  the  North  and  the  South  Downs.  This 
theory  will  be  better  understood  by  consulting  the  annexed  diagram 
(fig.  321.),  where  the  dark  lines  represent  what  now  remains,  and  the 
fainter  ones  those  portions  of  rock  which  are- believed  to  have  been 
carried  away. 

At  each  end  of  the  diagram  the  tertiary  strata  (No.  1.)  are  ex- 
hibited reposing  on  the  chalk.  In  the  middle  are  seen  the  Hastings 
sands  (No.  6.)  forming  an  anticlinal  axis,  on  each  side  of  which  the 
other  formations  are  arranged  with  an  opposite  dip.  It  has  been 
necessary,  however,  in  order  to  give  a  clear  view  of  the  different 
formations,  to  exaggerate  the  proportional  height  of  each  in  compa- 
rison to  its  horizontal  extent;  and  a  true  scale  is  therefore  subjoined 
in  another  diagram  (fig.  322.),  in  order  to  correct  the  erroneous 
impression  which  might  otherwise  be  made  on  the  reader's  mind. 
In  this  section  the  distance  between  the  North  and  South  Downs  is 
represented  to  exceed  forty  miles  ;  for  the  Valley  of  the  Weald  is 
here  intersected  in  its  longest  diameter,  in  the  direction  of  a  line 
between  Lewes  and  Maidstone. 

Through  the  central  portion,  then,  of  the  district  supposed  to  be 
denuded  runs  a  great  anticlinal  line,  having  a  direction  nearly  east 
and  west,  on  both  sides  of  which  the  beds  5,  4,  3,  and  2  crop  out  in 
succession.  But,  although,  for  the  sake  of  rendering  the  physical 
structure  of  this  region  more  intelligible,  the  central  line  of  elevation 
has  alone  been  introduced,  as  in  the  diagrams  of  Smith,  Mantell, 
Conybeare,  and  others,  geologists  have  always  been  well  aware  that 

T 


274 


VALLEY   OF    THE    WEALD. 

ft 

I 


« 

S" 


s  si 
If 


Mile 


[Cn.  XIX. 


I 


s 

8-S 
S  3 


numerous  minor  lines  of  dislocation  and  flexure  run  parallel  to  the 
great  central  axis. 

In  the  central  area  of  the  Hastings  sand  the  strata  have  under- 
gone the  greatest  displacement ;  one  fault  being  known,  where  the 


CH.  XIX.] 


CHALK   ESCARPMENTS. 


275 


vertical  shift  of  a  bed  of  calcareous  grit  is  no  less  than  60  fathoms.* 
Much  of  the  picturesque  scenery  of  this  district  arises  from  the 
depth  of  the  narrow  valleys  and  ridges  to  which  the  sharp  bends  and 
fractures  of  the  strata  have  given  rise ;  but  it  is  also  in  part  to  be 
attributed  to  the  excavating  power  exerted  by  water,  especially  on 
the  interstratified  argillaceous  beds. 

Besides  the  series  of  longitudinal  valleys  and  ridges  in  the  Weald, 

there  are  valleys  which  run  in 
g   a  transverse  direction,  passing 
<   through  the  chalk  to  the  basin 
^  I   of  the  Thames  on  the  one  side, 
|  *    and  to  the   English  Channel 
£       on  the  other.     In  this  manner 
|       the  chain  of  the  North  Downg 
is  broken  by  the  rivers  Wey, 
J       Mole,   Darent,    Medway,  and 
|   .    Stour;  the   South  Downs  by 
•3  §   the   Arun,   Adur,   Ouse,   and 
Cuckmere.f      If  these  trans- 
verse hollows  could  be   filled 
up,  all  the  rivers,  observes  Dr. 
Conybeare,   would  be   forced 
to  take  an  easterly  course,  and 
to  empty  themselves  into  the 
sea  by  Romney    Marsh   and 
Pevensey  Levels. 

Mr.  Martin  has  suggested 
that  the  great  cross  fractures 
of  the  chalk,  which  have  be- 
come river-channels,  have  a 
remarkable  correspondence  on 
each  side  of  the  valley  of  the 
Weald;  in  several  instances 
the  gorges  in  the  North  and 
South  Downs  appearing  to  be 
directly  opposed  to  each  other. 
Thus,  for  example,  the  defiles 
of  the  Wey  in  the  North 
Downs,  and  of  the  Arun  in 
the  South,  seem  to  coincide 
in  direction  ;  and,  in  like  man- 
ner, the  Ouse  corresponds  to 
the  Darent,  and  the  Cuckmere 
to  the  Medway.J 

Although  these  coincidences 
may,  perhaps,  be  accidental,  it 
is  ,by  no  means  improbable,  as 

;  Geol.  of  Western  Sussex,  p.  61. 


*  Fitton,  Geol.  of  Hastings,  p.  55. 
'f  Conybeare,  Outlines  of  Geol.,  p.  81. 


T  2 


276 


CHALK    ESCARPMENTS. 


[Cn.  XIX. 


hinted  by  the  author  above  mentioned,  that  great  amount  of  ele- 
vation towards  the  centre  of  the  Weald  district  gave  rise  to  trans- 
verse fissures.  And  as  the  longitudinal  valleys  were  connected 
with  that  linear  movement  which  caused  the  anticlinal  lines  running 
east  and  west,  so  the  cross  fissures  might  have  been  occasioned  by 
the  intensity  of  the  upheaving  force  towards  the  centre  of  the  line. 

But  before  treating  of  the  manner  in  which  the  upheaving  move- 
ment may  have  acted,  I  shall  endeavour  to  make  the  reader  more 
intimately  acquainted  with  the  leading  geographical  features  of  the 
district,  so  far  as  they  are  of  geological  interest. 

In  whatever  direction  we  travel  from  the  tertiary  strata  of  the 
basins  of  London  and  Hampshire  towards  the  valley  of  the  Weald, 
we  first  ascend  a  slope  of  white  chalk,  with  flints,  and  then  find 
ourselves  on  the  summit  of  a  declivity  consisting,  for  the  most  part, 
of  different  members  of  the  chalk  formation  ;  below  which  the 
Upper  Greensand,  and  sometimes,  also,  the  Gault,  crop  out.  This 
steep  declivity  is  the  great  escarpment  of  the  chalk  before  mentioned, 
which  overhangs  a  valley  excavated  chiefly  out  of  the  argillaceous 
or  marly  bed,  termed  Gault  (No.  3.).  The  escarpment  is  continuous 
along  the  southern  termination  of  the  North  Downs,  and  may  be 
traced  from  the  sea,  at  Folkestone,  westward  to  Guildford  and  the 
neighbourhood  of  Petersfield,  and  from  thence  to  the  termination  of 
the  South  Downs  at  Beachy  Head.  In  this  precipice  or  steep  slope 
the  strata  are  cut  off  abruptly,  and  it  is  evident  that  they  must 
originally  have  extended  farther.  In  the  wood-cut  (fig.  323.  p.  275.) 
part  of  the  escarpment  of  the  South  Downs  is  faithfully  represented, 
where  the  denudation  at  the  base  of  the  declivity  has  been  some- 
what more  extensive  than  usual,  in  consequence  of  the  Upper  and 
Lower  Greensand  being  formed  of  very  incoherent  materials,  the 
former,  indeed,  being  extremely  thin  and  almost  wanting. 

The  geologist  cannot  fail  to  recognise  in  this  view  the  exact 
likeness  of  a  sea-cliff;  and  if  he  turns  and  looks  in  an  opposite 
direction,  or  eastward,  towards  Beachy  Head  (see  fig.  324.),  he  will 


Fig.  324. 


Chalk  escarpment,  as  seen  from  the  hill  above  Steyning,  Sussex.    The  castle  and  village 
of  Bramber  iu  the  foreground. 

see  the  same  line  of  heights  prolonged.  Even  those  who  are  not 
accustomed  to  speculate  on  the  former  changes  which  the  surface  has 
undergone  may  fancy  the  broad  and  level  plain  to  resemble  the  flat 
sands  which  were  laid  dry  by  the  receding  tide,  and  the  different 


CH.  XIX.] 


TRANSVERSE    VALLEYS. 


277 


projecting  masses  of  chalk  to  be  the  headlands  of  a  coast  which 
separated  the  different  bays  from  each  other. 

Occasionally  in  the  North  Downs  sand-pipes  are  intersected  in  the 
slope  of  the  escarpment,  and  have  been  regarded  by  some  geologists 
as  more  modern  than  the  slope ;  in  which  case  they  might  afford  an 
argument  against  the  theory  of  these  slopes  having  originated  as  sea- 
cliffs  or  river-cliffs.  But,  when  we  observe  the  great  depth  of  many 
sand-pipes,  those  near  Sevenoaks,  for  example,  we  perceive  that  the 

lower  termination  of  such  pipes 
must  sometimes  appear  at  the 
surface  far  from  the  summit  of 
an  escarpment,  whenever  por- 
tions of  the  chalk  are  cut  away. 
In  regard  to  the  transverse 
valleys  before  mentioned,  as  in- 
S  tersecting  the  chalk  hills,  some 
|  idea  of  them  may  be  derived 
£  from  the  subjoined  sketch  (fig. 
§  325.)  of  the  gorge  of  the  River 
c  Adur,  taken  from  the  summit  of 
the  chalk-downs,  at  a  point  in 
the  bridle-way  leading  from  the 
towns  of  Bramber  and  Steyning 
to  Shoreham.  If  the  reader  will 
refer  again  to  the  view  given 
in  a  former  woodcut  (fig.  323. 
p.  275.),  he  will  there  see  the 
exact  point  where  the  gorge  of 
which  I  am  now  speaking  in- 
terrupts the  chalk  escarpment. 
A  projecting  hill,  at  the  point  a, 
hides  the  town  of  Steyning,  near 
which  the  valley  commences 
where  the  Adur  passes  directly 
to  the  sea  at  Old  Shoreham.  The 
river  flows  through  a  nearly 
level  plasin,  as  do  most  of,  the 
others  which  intersect  the  hills 
of  Surrey,  Kent,  and  Sussex; 
and  it  is  evident  that  these  open- 
ings could  not  have  been  pro- 
duced by  rivers,  except  under 
conditions  of  physical  geography 
entirely  different  from  those  now 
prevailing.  Indeed,  many  of  the 
existing  rivers,  like  the  Ouse 
near  Lewes,  have  filled  up  arms 
of  the  sea,  instead  of  deepening 
the  hollows  which  they  traverse. 

T  3 


278 


COOMB    NEAR    LEWES. 


[Cn.  XIX. 


That  the  place  of  some,  if  not  of  all,  the  gorges  running  north  and 
south,  has  been  originally  determined  by  the  fracture  and  displace- 
ment of  the  rocks,  seems  the  more  probable,  when  we  reflect  on  the 
proofs  obtained  of  a  ravine  running  east  and  west,  which  branches 
off  from  the  eastern  side  of  the  valley  of  the  Ouse  just  mentioned, 
and  which  is  undoubtedly  due  to  dislocation.  This  ravine  is  called 
"the  Coomb"  (fig.  326.),  and  is  situated  in  the  suburbs  of  the  town 


The  Coomb,  near  Lewes. 

of  Lewes.  It  was  first  traced  out  by  Dr.  Mantell,  in  whose  com- 
pany I  examined  it.  The  steep  declivities  on  each  side  are  covered 
with  green  turf,  as  is  the  bottom,  which  is  perfectly  dry.  No  out- 
ward signs  of  disturbance  are  visible ;  and  the  connection  of  the 
hollow  with  subterranean  movements  would  not  have  been  suspected 
by  the  geologist,  had  not  the  evidence  of  great  convulsions  been 
clearly  exposed  in  the  escarpment  of  the  valley  of  the  Ouse,  and  the 
numerous  chalk -pits  worked  at  thu  termination  of  the  Coomb.  By 
the  aid  of  these  we  discover  that  the  ravine  coincides  precisely  with 
a  line  of  fault,  on  one  stde  of  which  the  chalk  with  flints  (a,  fig.  327.) 


Fig.  327. 


Fault  coinciding  with  the  Coomb,  in  the  Cliff-hill  near  Lewes.    Mantell. 
a.  Chalk  with  flints.  b.  Lower  chalk. 


appears  at  the  summit  of  the  hill,  while  it  is  thrown  down  to  the 
bottom  on  the  other. 

In  order  to  account  for  the  manner  in  which  the  five  groups  of 


CH.  XIX.] 


PROMINENCE   OF   HARDER   STRATA. 


279 


strata,  2,  3,  4,  5,  6,  represented  in  the  map,  fig.  320.,  and  in  the 
section,  fig.  321.,  may  have  been  brought  into  their  present  position, 
the  following  hypothesis  has  been  suggested :  —  Suppose  the  five 
formations  to  lie  in  horizontal  stratification  at  the  bottom  of  the  sea ; 
then  let  a  movement  from  below  press  them  upwards  into  the  form 
of  a  flattened  dome,  and  let  the  crown  of  this  dome  be  afterwards  cut 
off,  so  that  the  incision  should  penetrate  to  the  lowest  of  the  five 
groups.  The  different  beds  would  then  be  exposed  on  the  surface, 
in  the  manner  exhibited  in  the  map,  fig.  320.* 

The  quantity  of  denudation,  or  removal  by  water,  of  stratified 
masses  assumed  to  have  once  reached  continuously  from  the  North 
to  the  South  Downs  is  so  enormous,  that  the  reader  may  at  first  be 
startled  by  the  boldness  of  the  hypothesis.  But  the  difficulty  will 
disappear  when  once  sufficient  time  is  allowed  for  the  gradual  rising 
and  sinking  of  the  strata  at  many  successive  geological  periods, 
during  which  the  waves  and  currents  of  the  ocean,  and  the  power  of 
rain,  rivers,  and  land-floods,  might  slowly  accomplish  operations 
which  no  sudden  diluvial  rush  of  waters  could  possibly  effect. 

Among  other  proofs  of  the  action  of  water,  it  may  be  stated  that 
the  great  longitudinal  valleys  follow  the  outcrop  of  the  softer  and 
more  incoherent  beds,  while  ridges  or  lines  of  cliff  usually  occur  at 
those  points  where  the  strata  are  composed  of  harder  stone.  Thus, 
for  example,  the  chalk  with  flints,  together  with  the  subjacent  upper 
greensand,  which  is  often  used  for  building,  under  the  provincial 
name  of  "  firestone,"  have  been  cut  into  a  steep  cliff  on  that  side  on 
which  the  sea  encroached.  This  escarpment  bounds  a  deep  valley, 
excavated  chiefly  out  of  the  soft  argillaceous  bed,  termed  gault 
(No.  3.,  map,  p.  273.).  In  some  places  the  upper  greensand  is  in  a 
loose  and  incoherent  state,  and  there  it  has  been  as  much  denuded  as 
the  gault ;  as,  for  example,  near  Beachy  Head ;  but  farther  to  the 
westward  it  is  of  great  thickness,  and  contains  hard  beds  of  blue 
chert  and  calcareous  sandstone  or  firestone.  Here,  accordingly,  we 
find  that  it  produces  a  corresponding  influence  on  the  scenery  of  the 
country ;  for  it  runs  out  like  a  step  beyond  the  foot  of  -the  chalk- 
hills,  and  constitutes  a  lower  terrace,  varying  in  breadth  from  a 
quarter  of  a  mile  to  three  miles,  and  following  the  sinuosities  of  the 
chalk-escarpment.f 


Fig.  328 


a.  Chalk  with  flints. 

c.  Upper  greensand,  or  firestone. 


ft.  Chalk  without  flints. 
d.  Gault. 


*  See  illustrations  of  this  theory,  by 
Dr.  Fitton,  Geol.  Sketch  of  Hastings. 


f  Sir  B.  Murchison,  Geol.  Sketch  of 


Sussex,  &c.,  Geol.  Trans.,  Second  Series, 
vol.  ii.  p.  98. 


T  4 


280  DENUDATION   OF   THE   WEALD.  [Cn.  XIX. 

It  is  impossible  to  desire  a  more  satisfactory  proof  that  the  escarp- 
ment is  due  to  the  excavating  power  of  water  during  the  rise  of  the 
strata,  or  during  their  rising  and  sinking  at  successive  periods ;  for 
I  have  shown,  in  my  account  of  the  coast  of  Sicily  (p.  76.),  in  what 
manner  the  encroachments  of  the  sea  tend  to  efface  that  succession  of 
terraces  which  must  otherwise  result  from  the  intermittent  upheaval 
of  a  coast  preyed  upon  by  the  waves.  During  the  interval  between 
two  elevatory  movements,  the  lower  terrace  will  usually  be  destroyed, 
wherever  it  is  composed  of  incoherent  materials ;  whereas  the  sea 
will  not  have  time  entirely  to  sweep  away  another  part  of  the  same 
terrace,  or  lower  platform,  which  happens  to  be  composed  of  rocks  of 
a  harder  texture,  and  capable  of  offering  a  firmer  resistance  to  the 
erosive  action  of  water.  As  the  yielding  clay  termed  gault  would  be 
readily  washed  away,  we  find  its  outcrop  marked  everywhere  by  a 
valley  which  skirts  the  base  of  the  chalk-hills,  and  which  is  usually 
bounded  on  the  opposite  side  by  the  lower  greensand;  but  as  the 
upper  beds  of  this  last  formation  are  most  commonly  loose  and  inco- 
herent, they  also  have  usually  disappeared  and  increased  the  breadth 
of  the  valley.  In  those  districts,  however,  where  chert,  limestone, 
and  other  solid  materials  enter  largely  into  the  composition  of  this 
formation  (No.  4.,  map,  p.  273.),  they  give  rise  to  a  range  of  hills 
parallel  to  the  chalk,  which  sometimes  rival  the  escarpment  of  the 
chalk  itself  in  height,  or  even  surpass  it,  as  in  Leith  Hill,  near 
Dorking.  This  ridge  often  presents  a  steep  escarpment  towards  the 
soft  argillaceous  deposit  called  the  Weald  clay  (No.  5. ;  see  the  dark 
tint  in  fig.  321.  p.  274.),  which  usually  forms  a  broad  valley,  sepa- 
rating the  lower  greensand  from  the  Hastings  sands  or  Forest 
Ridge ;  but  where  subordinate  beds  of  sandstone  of  a  firmer  texture 
occur,  the  uniformity  of  the  plain  of  No.  5.  is  broken  by  waring 
irregularities  and  hillocks. 

Pluvial  action.  —  In  considering,  however,  the  comparative  de- 
structibility  of  the  harder  and  softer  rocks,  we  must  not  underrate 
the  power  of  rain.  The  chalk-downs,  even  on  their  summits,  are 
usually  covered  with  unrounded  chalk-flints,  such  as  might  remain 
after  masses  of  white  chalk  had  been  softened  and  removed  by  water. 
This  superficial  accumulation  of  the  hard  or  siliceous  materials  of 
disintegrated  strata  may  be  due  in  no  small  degree  to  pluvial  action ; 
for  during  extraordinary  rains  a  rush  of  water  charged  with  cal- 
careous matter,  of  a  milk-white  colour,  may  be  seen  to  descend  even 
gently  sloping  hills  of  chalk.  If  a  layer  no  thicker  than  the  tenth 
of  an  inch  be  removed  once  in  a  century,  a  considerable  mass  may 
in  the  course  of  indefinite  ages  melt  away,  leaving  nothing  save  a 
stratum  of  flinty  nodules  to  attest  its  former  existence.  A  bed  of  fine 
clay  sometimes  covers  the  surface  of  slight  depressions  in  the  white 
chalk,  which  may  represent  the  aluminous  residue  of  the  rock,  after 
the  pure  carbonate  of  lime  has  been  dissolved  by  rain-water,  charged  * 
with  excess  of  carbonic  acid  derived  from  decayed  vegetable  matter. 
The  acidulous  waters  sometimes  descend  through  "  sand-pipes  "  and 
"swallow-holes"  in  the  chalk,  so  that  the  surface  may  be  under- 


CH.  XIX.]         THEORY   OF   FKACTUKE   AND   UPHEAVAL.  281 

mined,-  and  cavities  may  be  formed  or  enlarged,  even  by  that  part  of 
the  drainage  which  is  subterranean.* 

Lines  of  Fracture. — Mr.  Martin,  in  his  work  on  the  geology  of 
Western  Sussex,  published  in  1828,  threw  much  light  on  the  struc- 
ture of  the  Wealden  by  tracing  out  continuously  for  miles  the  direc- 
tion of  many  anticlinal  lines  and  cross  fractures  ;  and  the  same 
course  of  investigation  has  since  been  followed  out  in  greater  detail 
by  Mr.  Hopkins.  The  geologist  and  mathematician  last-mentioned 
has  shown  that  the  observed  direction  of  the  lines  of  flexure  and 
dislocation  in  the  Weald  district  coincide  with  those  which  might 
have  been  anticipated  theoretically  on  mechanical  principles,  if  we 
assume  certain  simple  conditions  under  which  the  strata  were  lifted 
up  by  an  expansive  subterranean  force. j" 

His  opinion,  that  both  the  longitudinal  and  transverse  lines  of 
fracture  may  have  been  produced  simultaneously,  accords  well  with 
that  expressed  by  M.  Thurmann,  in  his  work  on  the  anticlinal  ridges 
and  valleys  of  elevation  of  the  Bernese  Jura.J  For  the  accuracy 
of  the  map  and  sections  of  the  Swiss  geologist  I  can  vouch,  from 
personal  examination,  in  1835,  of  part  of  the  region  surveyed  by  him. 
Among  other  results,  at  which  he  arrived,  it  appears  that  the 
breadth  of  the  anticlinal  ridges  and  dome-shaped  masses  in  the  Jura 
is  invariably  great  in  proportion  to  the  number  of  the  formations 
exposed  to  view ;  or,  in  other  words,  to  the  depth  to  which  the  super- 
imposed groups  of  secondary  strata  have  been  laid  open.  (See  fig.  71. 
p.  55.  for  structure  of  Jura.)  He  also  remarks,  that  the  anticlinal 
lines  are  occasionally  oblique  and  cross  each  other,  in  which  case  the 
greatest  dislocation  of  the  beds  takes  place.  Some  of  the  cross  frac- 
tures are  imagined  by  him  to  have  been  contemporaneous  with  others 
subsequent  to  the  longitudinal  ones. 

I  have  assumed,  in  the  former  part  of  this  chapter,  that  the  rise  of 
the  Weald  was  gradual,  whereas  many  geologists  have  attributed  its 
elevation  to  a  single  effort  of  subterranean  violence.  There  appears 
to  them  such  a  unity  of  effect  in  this  and  other  lines  of  deranged 
strata  in  the  south-east  of  England,  such  as  that  of  the  Isle  of  Wight, 
as  is  inconsistent  with  the  supposition  of  a  great  number  of  separate 
movements  recurring  after  long  intervals  of  time.  But  we  know  that 
earthquakes  are  repeated  throughout  a  long  series  of  ages  in  the 
same  spots,  like  volcanic  eruptions.  The  oldest  lavas  of  Etna  were 
poured  out  many  thousands,  perhaps  myriads  of  years  before  the 
newest,  and  yet  they,  and  the  movements  accompanying  their  emission, 
have  produced  a  symmetrical  mountain  ;  and  if  rivers  of  melted 
matter  thus  continue  to  flow  upwards  in  the  same  direction,  and 
towards  the  same  point,  for  an  indefinite  lapse  of  ages,  what  diffi- 
culty is  there  in  conceiving  that  the  subterranean  volcanic  force, 
occasioning  the  rise  or  fall  of  certain  parts  of  the  earth's  crust, 

*  See  above,  p.  82,  83.  "  Sand-pipes        f  Geol.  Soc.  Proceed.  No.  74.  p.  363. 
in  Chalk  ;"  and  Prestwich,  Geol.  Quart.     1841,  and  G.  S.  Trans.  2  Ser.  vol.  7. 
Journ.  vol.  x.  p.  222.  %  Soulevemens  Jurassiques.     1832. 


282       PERIODS    OF    DENUDATION    OF    THE   WEALD.       [Cn.  XIX. 

may,  by  reiterated  movements,  produce  the  most  perfect  unity  of 
result  ? 

At  what  periods  the  Weald  valley  was  denuded.  —  We  may  next 
inquire  at  what  time  the  denudation  of  the  Weald  was  effected,  and 
we  shall  find,  on  considering  all  the  facts  brought  to  light  by  recent 
investigation,  that  it  was  accomplished  in  the  course  of  so  long  a 
series  of  ages,  that  the  greatest  revolutions  in  the  physical  geography 
of  the  globe,  yet  known  to  us,  have  taken  place  within  the  same 
lapse  of  time.  It  has  now  been  ascertained,  that  part  of  the  denu- 
dation of  the  Weald  was  completed  before  the  British  Eocene  strata, 
and  consequently  before  the  nummulitic  .rocks  of  Europe  and  Asia 
were  formed.  The  date,  therefore,  of  part  of  the  changes  now  under 
contemplation  was  long  antecedent  to  the  existence  of  the  Alps, 
Pyrenees,  and  many  other  European  and  Asiatic  mountain-chains, 
and  even  to  the  accumulation  of  large  portions  of  their  component 
materials  beneath  the  sea. 

M.  Elie  de  Beaumont  suggested,  in  1833,  that  there  was  an  island 
in  the  Eocene  sea  in  the  area  now  occupied  by  the  French  and 
English  Wealden  strata,  and  he  gave  a  map  or  hypothetical  restora- 
tion of  the  ancient  geography  of  that  region  at  the  era  alluded  to.* 
Mr.  Prestwich  has  since  shown  that  the  materials  of  which  the 
lower  tertiary  beds  of  England  are  made  up,  and  their  manner  of 
resting  on  the  chalk,  imply,  that  such  an  island,  or  several  islands 
and  shoals,  composed  of  Chalk,  Upper  Greensand,  Gault,  and  pro- 
bably of  some  of  the  Lower  Cretaceous  rocks,  did  exist  somewhere 
between  the  present  North  and  South  Downs.  The  undermined 
cliffs  and  shores  of  those  lands  supplied  the  flints,  which  the  action 
of  the  waves  rounded  into  pebbles,  such  as  now  form  the  Woolwich 
and  Blackheath  shingle-beds  below  the  London  Clay.  It  is  sup- 
posed, that  the  land  referred  to  was  drained  by  rivers  flowing  into 
the  Eocene  sea,  and  whence  the  brackish  and  freshwater  deposits  of 
Woolwich  and  other  contemporaneous  strata  f  were  derived.  The 
large  size  of  some  of  the  rolled  flints  (eight  inches  and  upwards  in 
diameter)  of  the  Blackheath  shingle  demonstrates  the  proximity  of 
land.  Such  heavy  masses  could  not  have  been  transported  from 
great  distances,  whether  they  owe  their  shape  to  waves  breaking  on 
a  sea-beach,  or  to  rivers  descending  a  steep  slope. 

In  the  annexed  diagram  (fig.  329.)  Mr.  Prestwich  has  represented 
a  section  from  near  Saffron  Walden,  in  Essex,  to  the  Weald,  passing 
north  and  south  through  Godstone,  in  which  we  see  how  the  chalk, 
c,  had  been  disturbed  and  denuded  before  the  lower  Eocene  beds,  b, 
were  deposited.  Some  small  patches  of  the  last-mentioned  beds,  bf, 
consisting  of  clay  and  sand,  extend  occasionally,  as  in  this  instance, 
to  the  very  edge  of  the  escarpment  of  the  North  Downs,  proving  that 
the  surface  of  the  white  chalk,  now  covered  with  tertiary  strata,  is 
the  same  which  originally  constituted  the  bottom  of  the  Eocene  sea. 

*  Mem.  de  la  Soc.  Geol.  de  France,         f  See  p.  221.  above, 
vol.  i.  part  L  p.  111.  pi.  7.  fig.  5. 


CH.  XIX.]  ISLANDS   IN   THE   EOCENE   SEA.  283 

Fig.  329. 


Section  showing  that  the  Weald  had  been  denuded  of  chalk  before  the  Lower  Eocene  strata  were 

deposited. 

S.  Relative  position  of  Saffron  Walden. 

G.  Chalk-escarpment  above  Godstone,  surmounted  by  a  patch  of  the  Lower  Tertiary  beds,  b'. 
a.  London  Clay.  6,  b'.  Lower  Tertiaries.  c.  Chalk. 

d.  Upper  Greensand.  e.  Gault.  /.  Lower  Greensand  and  Wealden. 

x.  Point  at  which  the  present  upper  and  under  surfaces  of  the  chalk,  if  they  were  prolonged,  would 
converge. 

'  It  is  therefore  inferred,  that,  if  we  prolong  southwards  the  upper 
and  under  surfaces  of  the  chalk,  along  the  dotted  line  in  the  above 
section,  they  would  converge  at  the  point  x ;  therefore,  beyond  that 
point,  no  white  chalk  existed  at  the  time  when  the  Eocene  beds,  b,  b', 
were  formed.  In  other  words,  the  central  parts  of  the  Wealden, 
south  of  x,  were  already  bared  of  their  original  covering  of  chalk, 
or  had  only  some  slight  patches  of  that  rock  scattered  over  them. 

The  island,  or  islands,  in  the  Eocene  sea  may  be  represented  in 
the  annexed  diagram  (fig.  330.) ;  but  doubtless  the  denudation  ex- 
Fig.  330. 


Sea. 


Island  in  the  Eocene  Sea. 
a.  Chalk,  Upper  Greensand,  and  Gault.  6.  Lower  Greensand. 


c.  Wealden. 


tended  farther  in  width  and  depth  before  the  close  of  the  Eocene 
period,  and  the  waves  may  have  cut  into  the  Lower  Greensand,  and 
perhaps  in  some  places  into  the  Wealden  strata. 

According  to  this  view  the  mass  of  cretaceous  and  subcretaceous 
rocks,  planed  off  by  the  waves  and  currents  in  the  area  between 
the  North  and  South  Downs  before  the  origin  of  the  oldest  Eocene 
beds,  may  have  been  as  voluminous  as  the  mass  removed  by  denu- 
dation since  the  commencement  of  the  Eocene  era. 

But  the  reader  may  ask,  why  is  it  necessary  to  assume  that  so 
much  white  chalk  first  extended  continuously  over  the  Wealden 
beds  in  this  part  of  England,  and  was  then  removed  ?  May  we  not 
suppose  that  land  began  to  exist  between  the  North  and  South 
Downs  at  a  much  earlier  epoch ;  and  that  the  upper  Wealden  beds 
rose  in  the  midst  of  the  Cretaceous  Ocean,  so  as  to  check  the  accu- 
mulation of  white  chalk,  and  limit  it  to  the  deeper  water  of  adjoining 
areas  ?  This  hypothesis  has  often  been  advanced,  and  as  often 
rejected ;  for,  had  there  been  shoals  or  dry  land  so  near,  the  white 


284  AT    WHAT    PERIODS  [Cu.  XIX. 

chalk  would  not  have  remained  unsoiled,  or  without  intermixture  of 
mud  and  sand  ;  nor  would  organic  remains  of  terrestrial,  fluviatile,  or 
littoral  origin  have  been  so  entirely  wanting  in  the  strata  of  the 
North  and  South  Downs,  where  the  chalk  terminates  abruptly  in 
the  escarpments.  It  is  admitted  that  the  fossils  now  found  there 
belong  exclusively  to  classes  which  inhabit  a  deep  sea.  Moreover, 
the  uppermost  beds  of  the  Wealden  group,  as  Mr.  Prestwich  has 
remarked,  would  not  have  been  so  strictly  conformable  with  the 
lowest  beds  of  the  Lower  Greensand  had  the  strata  of  the  Wealden 
undergone  upheaval  before  the  deposition  of  the  incumbent  creta- 
ceous series. 

But,  although  we  must  assume  that  the  white  chalk  was  once 
continuous  over  what  is  now  the  Weald,  it  by  no  means  follows  that 
the  first  denudation  was  subsequent  to  the  entire  Cretaceous  era. 
Most  probably  it  commenced  before  a  large  portion  of  the  Maestricht 
beds  were  formed,  or  while  they  were  in  progress.  I  have  already 
stated  (p.  239.  above),  that  in  parts  of  Belgium  I  observed  rolled 
pebbles  of  chalk-flints  very  abundant  in  the  lowest  Maestricht  beds, 
where  these  last  overlie  the  white  chalk,  showing  at  how  early  a 
date  the  chalk  was  upraised  from  deep  water  and  exposed  to  aqueous 
abrasion. 

Guided  by  the  amount  of  change  in  organic  life,  we  may  estimate 
the  interval  between  the  Maestricht  beds  and  the  Thanet  Sands  to 
have  been  nearly  equal  in  duration  to  the  time  which  elapsed 
between  the  deposition  of  those  same  Thanet  Sands  and  the  Glacial 
period.  If  so,  it  would  be  idle  to  expect  to  be  able  to  make  ideal 
restorations  of  the  innumerable  phases  in  physical  geography  through 
which  the  south-east  of  England  must  have  passed  since  the  Weald 
began  to  be  denuded.  In  less  than  half  the  same  lapse  of  time  the 
aspect  of  the  whole  European  area  has  been  more  than  once  entirely 
changed.  Nevertheless,  it  may  be  useful  to  enumerate  some  of  the 
known  fluctuations  in  the  physical  conformation  of  the  Weald  and 
the  regions  immediately  adjacent  during  the  period  alluded  to. 

First,  we  have  to  carry  back  our  thoughts  to  those  very  remote 
movements  which  first  brought  up  the  white  chalk  from  a  deep  sea 
into  exposed  situations  where  the.  waves  could  plane  off  certain 
portions,  as  expressed  in  diagram,  fig.  329.,  before  the  British  Lower 
Eocene  beds  originated. 

Secondly,  we  have  to  take  into  account  the  gradual  wear  and 
tear  of  the  chalk  and  its  flints,  to  which  the  Thanet  sands  bear 
witness,  as  well  as  the  subsequent  Woolwich  and  Blackheath  shingle- 
beds,  occasionally  50  feet  thick,  and  composed  of  rolled  flint-pebbles. 

Thirdly,  at  a  later  period  a  great  subsidence  took  place,  by  which 
the  shallow-water  and  fresh-water  beds  of  Woolwich  and  other 
Lower  Eocene  deposits  were  depressed  (see  above,  p.  222.)  so  as  to 
allow  the  London  Clay  and  Bagshot  series,  of  deep-sea  origin,  to 
accumulate  over  them.  The  amount  of  this  subsidence,  according 
to  Mr.  Prestwich,  exceeded  800  feet  in  the  London,  and  1800  feet 
in  the  Hampshire  or  Isle  of  Wight  basin  ;  and,  if  so,  the  intervening 


CH.  XIX.]  THE    WEALD    Vr  ALLEY    WAS   DENUDED.  285 

area  of  the  Weald  could  scarcely  fail  to  share  in  the  movement,  and 
some  parts  at  least  of  the  island  before  spoken  of  (fig.  330.  p.  283.) 
would  become  submerged. 

Fourthly.  After  the  London  clay  and  the  overlying  Bagshot  sands 
had  been  deposited,  they  appear  to  have  been  upraised  in  the  London 
basin,  during  the  Eocene  period,  and  their  conversion  into  land  in 
the  north  seems  to  have  preceded  the  upheaval  of  beds  of  correspond- 
ing age  in  the  south,  or  in  the  Hampshire  basin ;  because  none  of 
the  fluvio-marine  Eocene  strata  of  Hordwell  and  the  Isle  of  Wight 
(described  in  Ch.  XVI.)  are  found  in  any  part  of  the  London  area. 

Fifthly.  The  fossils  of  the  alternating  marine,  brackish,  and  fresh- 
water beds  of  Hampshire,  of  Middle  and  Upper  Eocene  date,  bear 
testimony  to  rivers  draining  adjacent  lands,  and  to  the  existence  of 
numerous  quadrupeds  in  those  lands.  Instead  of  these  phenomena, 
the  signs  of  an  open  sea  might  naturally  have  been  expected,  as  a 
consequence  of  the  vast  subsidence  of  the  Middle  Eocene  beds  before 
mentioned,  had  not  some  local  upheaval  taken  place  at  the  same  time 
in  the  Isle  of  Wight  or  in  regions  immediately  adjacent.  Whatever 
hypothesis  be  adopted,  we  are  entitled  to  assume  that  during  the 
Middle  and  Upper  Eocene  periods  there  were  risings  and  sinkings  of 
land,  and  changes  of  level  in  the  bed  of  the  sea  in  the  south-east  of 
England,  and  that  the  movements  were  by  no  means  uniform  over 
the  whole  area  during  these  periods.  The  extent  and  thickness  of 
the  missing  beds  in  the  Weald  should  of  itself  lead  us  to  look  for  proofs 
of  that  area  having  by  repeated  oscillations  changed  its  level  fre- 
quently, and,  oftener  than  any  adjoining  area,  been  turned  from 
sea  into  land  ;  for  the  submergence  and  emergence  of  land  augment, 
beyond  any  other  cause,  the  wasting  and  removing  power  of  water, 
whether  of  the  waves  or  of  rivers  and  land-floods. 

Sixthly.  As  yet  we  have  discovered  no  marine  Miocene  (orfalu- 
nian)  formations  in  any  part  of  the  British  Isles,  nor  any  of  older 
Pliocene  date  south  of  the  Thames  ;  but  the  Upper  Eocene  strata  of 
the  Isle  of  Wight  (the  Hempstead  beds  before  described)  have  been 
upraised  above  the  level  of  the  sea  in  which  they  were  originally 
formed,  and  some  of  them  have  been  thrown  into  a  vertical  position, 
as  seen  in  Alum  and  Whitecliff  Bays,  attesting  great  movements  since 
the  origin  of  the  newest  tertiaries  of  that  district.  Such  movements 
may  have  occurred,  in  great  part  at  least,  during  the  Miocene  period, 
when  a  large  part  of  Europe  is  supposed  to  have  become  land  as 
before  suggested  (p.  181.).  Hence  we  are  entitled  to  speculate  on  the 
probability  of  revolutions  in  the  physical  geography  of  the  Weald 
in  times  intermediate  between  the  deposition  of  the  Hempstead  beds 
and  the  origin  of  the  Suffolk  crag. 

Seventhly.  But  we  have  still  to  consider  another  vast  interval  of 
time  —  that  which  separated  the  beginning  of  the  older  Pliocene  from 
the  beginning  of  the  Pleistocene  era,  —  a  lapse  of  ages  which,  if 
measured  by  the  fluctuations  experienced  in  the  marine  fauna,  may 
have  sufficed  to  uplift  or  sink  whole  continents  by  a  process  as  slow 
as  that  which  is  now  operating  in  Sweden  and  in  Greenland. 


286  WEALD,   WHEN   DENUDED.  [Cn.  XIX. 

Lastly.  The  reader  must  recall  to  mind  what  was  said,  in  the  llth 
and  12th  chapters,  of  the  glacial  drift  and  its  far-transported  mate- 
rials. How  wide  an  extent  of  the  British  Isles  appears  to  have  been 
under  the  sea  during  some  part  or  other  of  that  epoch !  Most  of  the 
submerged  areas  were  afterwards  converted  into  dry  land,  several 
hundred  and  in  some  places  more  than  a  thousand  feet  high.  It  is 
an  opinion  very  commonly  entertained,  that  the  central  axis  of  the 
Weald  was  dry  land  when  the  most  characteristic  northern  drift 
originated ;  no  traces  of  northern  erratics  having  been  met  with 
farther  south  than  Highgate  near  London.  If  such  were  the  case, 
the  Weald  was  probably  dry  land  at  the  era  when  the  buried  forest 
of  Cromer  in  Norfolk  (see  above,  p.  137.  and  154.)  flourished,  and 
when  the  elephant,  rhinoceros,  hippopotamus,  extinct  beaver,  and 
other  mammals  peopled  that  country.  It  may  also  be  presumed  that 
the  Weald  continued  above  the  sea-level  when  that  forest  sank  down 
to  receive  its  covering  of  boulder-clay,  gravel,  chalk-rubble,  and 
other  deposits,  several  hundred  feet  thick.  But  it  by  no  means 
follows  that  the  area  of  the  Weald  was  stationary  during  all  this 
period.  Its  surface  may  have  been  modified  again  and  again  during 
the  Glacial  era,  though  it  may  never  have  been  submerged  beneath 
the  sea. 

Mr.  Trimmer  has  represented  in  a  series  of  four  maps  his  views 
as  to  the  successive  changes  which  the  physical  geography  of  Eng- 
land and  parts  of  Europe  may  have  undergone,  after  the  commence- 
ment of  the  Glacial  epoch.*  In  the  last  but  one  of  these  he  places 
the  Weald  under  water  at  a  date  long  posterior  to  the  forest  of 
Cromer.  In  the  fourth  map  he  represents  the  Weald  as  recon- 
verted into  land  at  a  time  when  England  was  united  to  the  con- 
tinent, and  when  the  Thames  was  a  river  of  greater  volume  and  of 
more  easterly  extension  than  it  is  now,  as  proved  by  his  own  and 
Mr.  Austen's  observations  on  the  ancient  alluvium  of  the  Thames 
with  its  freshwater  fossils  at  points  very  near  the  sea.  To  discuss 
the  various  data  on  which  such  conclusions  depend,  would  lead  me 
into  too  long  a  digression ;  I  merely  allude  to  them  in  this  place 
to  show  that,  while  the  researches  of  Mr.  Prestwich  establish  the 
extreme  remoteness  of  the  period  when  the  denuding  operations 
began,  those  of  other  geologists  above  cited,  to  whom  Mr.  Martin, 
Professor  Morris,  and  Sir  R.  Murchison  should  be  added,  prove  that 
important  superficial  changes  have  occurred  at  very  modern  eras. 

In  Denmark,  especially  in  the  island  of  Moen,  Mr.  Puggaard  has 
demonstrated  that  strata  of  chalk  with  flints,  nearly  as  thick  as  the 
white  chalk  of  the  Isle  of  Wight  and  Purbeck,  have  undergone  dis- 
turbances and  contortions  since  the  northern  drift  was  formed.f  The 
layers  of  chalk-flint  exposed  in  lofty  sea-cliffs  are  often  vertical  and 
curved,  and  the  sands  and  clays  of  the  overlying  drift  follow  the  bend- 
ings  and  foldings  of  the  older  beds,  and  have  evidently  suffered  the 
same  derangement.  If,  therefore,  we  find  it  necessary,  in  order  to 

*  Geol.  Quart.  Journ.,  vol.  ix.  pi.  13.         f  Puggaard,   Moens   Geologic,   8vo. 

Copenhagen,  1851. 


CH.  XIX.] 


WEALD,    HOW   DENUDED. 


287 


explain  the  position  of  some  beds  of  gravel,  loam,  or  drift  in  the  south- 
east of  England,  to  imagine  important  dislocations  of  the  chalk  and 
local  changes  of  level  since  the  Glacial  period,  such  speculations  are 
in  harmony  with  conclusions  derived  from  independent  sources,  or 
drawn  from  the  exploration  of  foreign  countries. 

It  was  long  ago  observed  by  Dr.  Mantell  that  no  vestige  of  the 
chalk  and  its  flints  has  been  seen  on  the  central  ridge  of  the  Weald 
or  on  the  Hastings  Sands,  but  merely  gravel  and  loam  derived  from 
the  rocks  immediately  subjacent.  This  distribution  of  alluvium,  and 
especially  the  absence  of  chalk  detritus  in  the  central  district,  agrees 
well  with  the  theory  of  denudation  before  set  forth ;  for,  to  return  to 
fig.  321.  (p.  274.),  if  the  chalk  (No.  2.)  were  once  continuous  and 
covered  every  where  with  flint-gravel,  this  superficial  covering  would 
be  the  first  to  be  carried  away  from  the  highest  part  of  the  dome 
long  before  any  of  the  gault  (No.  3.)  was  laid  bare.  Now,  if  some 
ruins  of  the  chalk  remain  at  first  on  the  gault,  these  would  be,  in  a 
great  degree,  cleared  away  before  any  part  of  the  lower  greensand 
(No.  4.)  is  denuded.  Thus  in  proportion  to  the  number  and  thick- 
ness of  the  groups  removed  in  succession,  is  the  probability  lessened 
of  our  finding  any  remnants  of  the  highest  group  strewed  over  the 
bared  surface  of  the  lowest. 

But  it  is  objected,  that,  had  the  sea  at  one  or  several  periods  been 
the  agent  of  denudation,  we  should  have  found  ancient  sea-beaches 
at  the  foot  of  the  escarpments,  and  other  signs  of  oceanic  erosion. 
As  a  general  rule,  the  wreck  of  the  white  chalk  and  its  flints  can  only 
be  traced  to  slight  distances  from  the  escarpments  of  the  North  and 
South  Downs.  Some  exceptions  occur,  one  of  which  was  first  pointed 
out  to  me  in  1830,  by  the  late  Dr.  Mantell.  In  this  case  the  flints 
are  seen  near  Barcombe,  three  miles  from  the  nearest  chalk,  as  indi- 
cated in  the  annexed  section  (fig.  331.).  Even  here  it  will  be  seen 
that  the  gravel  reaches  no  farther  than  the  Weald  clay.  But 


Fig.  331. 


Section  from  the  north  escarpment  of  the  South  Downs  to  Barcombe. 
A.  Layer  of  unrounded  chalk- flints. 

1.  Gravel  composed  of  partially  rounded  chalk-flints. 

2.  Chalk  with  and  without  flints. 

3.  Lowest  chalk  or  chalk-marl  (upper  greensand  wanting). 

4.  Gault.  5.  Lower  greensand.  6.  Weald  clay. 

it  is  worthy  of  remark,  that  such  depressions  as  that  between 
Barcombe  and  Offham  in  this  section,  arising  from  the  facility  with 
which  the  argillaceous  gault  (No.  4.  map.  p.  273.)  has  been  removed 
by  water,  are  usually  free  from  superficial  detritus,  although  such 
valleys,  situated  at  the  foot  of  escarpments  where  there  has  been 
much  waste,  might  have  been  supposed  to  be  the  natural  receptacles 
of  the  wreck  of  the  undermined  cliffs.  The  question  is  therefore 


288 


ELEPHANT-BED. 


[Cn.  XIX. 


often  put  how  these  hollows  could  have  been  swept  clean  except  by 
some  extraordinary  catastrophe. 

The  frequent  angularity  of  the  flints  in  the  drift  of  Barcombe  and 
other  places  is  also  insisted  upon  as  another  indication  of  denuding 
causes  differing  in  kind  and  degree  from  any  which  man  has  witnessed. 
But  all  who  have  examined  the  gravel  at  the  base  of  a  chalk-cliff, 
in  places  where  it  is  not  peculiarly  exposed  to  the  continuous  and 
violent  action  of  the  waves,  are  aware  that  the  flints  retain  much 
angularity.  This  may  be  seen  between  the  Old  Harry  rocks  in 
Dorsetshire  and  Christchurch  in  Hampshire.  Throughout  the 
greater  part  of  that  line  of  coast  the  cliffs  are  formed  of  tertiary 
strata,  capped  by  a  dense  covering  of  gravel  formed  of  flints  slightly 
abraded.  As  the  waste  of  the  cliffs  is  rapid  the  old  materials  are 
gradually  changed  for  new  ones  on  the  beach  ;  nevertheless  we  have 
here  an  example  of  angles  being  retained  after  two  periods  of  attri- 
tion ;  first,  where  the  gravel  was  spread  originally  over  the  Eocene 
deposits  ;  and,  secondly,  after  the  Eocene  sands  and  clays  were  under- 
mined and  the  modern  cliff  formed. 

Angular  flint-breccia  is  not  confined  to  the  Weald,  nor  to  the 
transverse  gorges  in  the  chalk,  but  extends  along  the  neighbouring 
coast  from f  Brighton  to  Rottingdean,  where  it  was  called  by 
Dr.  Mantell  "  the  elephant-bed,"  because  the  bones  of  the  mammoth 
abound  in  it  with  those  of  the  horse  and  other  mammalia.  The 
following  is  a  section  of  this  formation  as  it  appears  in  the  Brighton 
cliff* 


Fig.  332 


A.  Chalk  with  layers  of  flint  dipping  slightly  to  the  south. 

b.  Ancient  beach,  consisting  ot  fine  sand,  from  one  to  four  feet  thick,  covered  by  shingle  from  five 

to  eight  feet  thick  of  pebbles  of  chalk-flint,  granite,  and  other  rocks,  with  broken  shells  of 
recent  marine  species,  and  bones  of  cetacea. 

c.  Elephant-bed,  about  fifty  feet  thick,  consisting  of  layers  of  white  chalk  rubble,  with  broken  chalk- 

flints,  often  more  confusedly  stratified  than  is  represented  in  this  drawing,  in  which  deposit 
are  found  bones  of  ox,  deer,  horse,  and  mammoth. 

d.  Sand  and  shingle  of  modern  beach. 


*  See  also  Sir  R.  Murchison,  Geol.  Quart.  Journ.  vol.  vii.  p.  365. 


CH.XIX.]  SANGATTE   CLIFF.  289 

To  explain  this  section  we  must  suppose  that,  after  the  excavation 
of  the  cliff  A,  the  beach  of  sand  and  shingle  b  was  formed  by  the 
long-continued  action  of  the  sea.  The  presence  of  Littorina  littorea 
and  other  recent  littoral  shells  determines  the  modern  date  of  the 
accumulation.  The  overlying  beds  are  composed  of  such  calcareous 
rubble  and  flints,  rudely  stratified,  as  are  often  conspicuous  in  parts 
of  the  Norfolk  coast,  where  they  are  associated  with  glacial  drift, 
and  were  probably  of  contemporaneous  origin.  Similar  flints  and 
chalk-rubble  have  been  recently  traced  by  Sir  Roderick  Murchison 
to  Folkestone  and  along  the  face  of  the  cliffs  at  Dover,  where  the 
teeth  of  the  fossil  elephant  have  been  detected. 

Mr.  Prestwich  also  has  shown  that  at  Sangatte,  near  Calais,  on  the 
coast  exactly  opposite  Dover,  a  similar  waterworn  beach,  with  an 
incumbent  mass  of  angular  flint-breccia,  is  visible.  I  have  myself 
visited  this  spot  and  found  the  deposit  strictly  analogous  to  that  of 
Brighton.  The  fundamental  ancient  beach  has  been  uplifted  more 
than  10  feet  above  its  original  level.  The  flint-pebbles  in  it  have 
evidently  been  rounded  at  the  base  of  an  ancient  chalk-cliff,  the 
course  of  which  can  still  be  traced  inland,  nearly  parallel  with  the 
present  shore,  but  with  a  space  intervening  between  them  of  about 
one  third  of  a  mile  in  its  greatest  breadth.  This  space  is  occupied  by 
a  terrace,  100  feet  in  its  greatest  height,  the  component  materials  of 
which  are  too  varied  and  complex  to  be  described  here.  They  are 
such  as  might,  I  conceive,  have  been  heaped  up  above  the  sea-level  in 
the  delta  of  a  river  draining  a  region  of  white  chalk.  The  delta  may 
perhaps  have  been  slowly  subsiding  while  the  strata  accumulated. 
Some  of  the  beds  of  chalk-rubble  with  broken  flints  appear  to  have 
had  channels  cut  in  them  before  the  uppermost -deposit  of  sand  and 
loam  was  thrown  down.  The  angularity  of  the  flints,  as  Mr.  Prest- 
wich has  suggested,  may  be  owing  to  their  having  been  previously 
shattered  when  in  the  body  of  the  chalk  itself;  for  we  often  see 
flints  so  fractured  in  situ  in  the  chalk,  especially  when  the  latter  has 
been  much  disturbed.  The  presence  also  in  this  Sangatte  drift  of 
large  fragments  of  angular  white  chalk,  some  of  them  two  feet  in 
diameter,  should  be  mentioned.  They  are  confusedly  mixed  with 
smaller  gravel  and  fine  mud,  for  the  most  part  devoid  of  stratifi- 
cation, and  yet  often  too  far  from  the  old  cliffs  to  have  been  a  talus. 
I  therefore  suspect  that  the  waters  of  the  river  and  its  tributaries 
were  occasionally  frozen  over,  and  that  during  floods  the  carrying 
power  of  ice  co-operated  with  that  of  water  to  transport  fragile 
rocks  and  angular  flints,  leaving  them  unsorted  when  the  ice  melted, 
or  not  arranged  according  to  size  and  weight  as  in  deposits  stratified 
by  moving  water.  A  climate  like  that  now  prevailing  on  the 
borders  of  the  Baltic  or  in  Canada  might  produce  such  effects  long 
after  the  intense  cold  of  the  glacial  epoch  had  passed  away.  The 
abundance  of  mammalia  in  countries  where  rivers  are  liable  to  be 
annually  encumbered  with  ice,  is  a  fact  with  which  we  are  familiar 
in  the  northern  hemisphere,  and  the  frequency  of  fossil  remains  of 
quadrupeds  in  formations  of  glacial  origin  ought  not  to  excite 


290  DENUDATION   OP   THE   WEALD.  [Cn.  XIX. 

surprise.  As  to  the  angularity  of  the  flints,  it  has  been  thought  by 
some  authorities  to  imply  great  violence  in  the  removing  power, 
especially  in  those  cases  where  well-rounded  pebbles  washed  out  of 
Eocene  strata  are  likewise  found  broken,  sometimes  with  sharp 
edges  and  often  with  irregular  pieces  chipped  out  of  them  as  if  by  a 
smart  blow.  Such  fractured  pebbles  occur  not  unfrequently  in  the 
drift  of  the  valley  of  the  Thames.  In  explanation  I  may  remark 
that,  in  the  Blackheath  and  other  Eocene  shingle-beds,  hard  egg- 
shaped  flint-pebbles  may  be  found  in  such  a  state  of  decomposition 
as  to  break  in  the  same  manner  on  the  application  of  a  moderate 
blow,  such  as  stones  might  encounter  in  the  bed  of  a  swollen  river. 

To  conclude :  It  is  a  fact,  not  questioned  by  any  geologist,  that 
the  area  of  the  Weald  once  rose  from  beneath  the  sea  after  the  origin 
of  the  chalk,  that  rock  being  a  marine  product,  and  now  constituting 
dry  land.  Few  will  question,  that  part  of  the  same  area  remained 
under  water  until  after  the  origin  of  the  Eocene  deposits,  because 
they  also  are  marine,  and  reach  to  the  edge  of  the  chalk-downs. 
Whether,  therefore,  we  do  or  do  not  admit  the  occurrence  of  reiter- 
ated submersions  and  emersions  of  land,  the  first  of  them  as  old  as 
the  Upper  Cretaceous,  the  last  perhaps  of  Newer  Pliocene  or  even 
later  date,  we  are  at  least  compelled  to  grant  that  there  was  a  time 
when,  in  the  region  under  consideration,  the  waters  of  the  sea 
retreated.  The  presence  of  land-  and  river-shells,  and  the  bones  of 
terrestrial  quadrupeds  in  some  of  the  gravel,  loam,  and  flint-breccia 
of  the  Weald  may  indicate  a  fluviatile  origin,  but  they  can  never 
disprove  the  prior  occupation  of  the  area  by  the  sea.  Heavy  rains, 
the  slow  decomposition  of  rocks  in  the  atmosphere,  land-floods,  and 
rivers  (some  of  them  larger  than  those1*  now  flowing  in  the  same 
valleys)  may  have  modified  the  surface  and  obliterated  all  signs  of 
the  antecedent  presence  of  the  sea.  Littoral  shells,  once  strewed 
over  ancient  shores,  or  buried  in  the  sands  of  the  beach,  may  have 
decomposed  so  as  to  make  it  impossible  for  us  to  assign  an  exact 
paleontological  date  to  the  older  acts  of  denudation ;  but  the  removal 
of  Chalk  and  Greensand  from  the  central  axis  of  the  Weald,  the 
leading  inequalities  of  hill  and  dale,  the  long  lines  of  escarpment,  the 
longitudinal  and  transverse  valleys,  may  still  be  mainly  due  to  the 
power  of  the  waves  and  currents  of  the  sea,  co-operating  with  that 
upheaval  and  subsidence  and  dislocation  of  rocks  which  all  admit 
to  have  taken  place. 

In  despair  of  solving  the  problem  of  the  present  geographical 
configuration  and  geological  structure  of  the  Weald  by  an  appeal 
to  ordinary  causation,  some  geologists  are  fain  to  invoke  the  aid 
of  imaginary  "rushes  of  salt  water"  over  the  land,  during  the 
sudden  upthrow  of  the  bed  of  the  sea,  when  the  anticlinal  axis 
of  the  Weald  was  formed.  Others  refer  to  vast  bodies  of  fresh  water 
breaking  forth  from  subterranean  reservoirs,  when  the  rocks  were 
riven  by  earthquake-shocks  of  intense  violence.  The  singleness  of 
the  cause  and  the  unity  of  the  result  are  emphatically  insisted  upon : 
the  catastrophe  was  abrupt,  tumultuous,  transient,  and  paroxysmal ; 


Cn.  XIX.]  CONCLUSION.  291 

fragments  of  stone  were  swept  along  to  great  distances  without  time 
being  allowed  for  attrition  ;  alluvium  was  thrown  down  unstratified, 
and  often  in  strange  situations,  on  the  flanks  or  on  the  summits  of 
hills,  while  the  lowest  levels  were  left  bare.  The  convulsion  was  felt 
simultaneously  over  so  wide  an  area  that  all  the  individuals  of 
certain  species  of  quadrupeds  were  at  once  annihilated ;  yet  the 
event  was  comparatively  modern,  for  the  species  of  testacea  now 
living  were  already  in  existence. 

This  hypothesis  is  surely  untenable  and  unnecessary.  In  the 
present  chapter  I  have  endeavoured  to  show  how  numerous  have 
been  the  periods  of  geographical  change,  and  how  vast  their  dura- 
tion. Evidence  to  this  effect  is  afforded  by  the  relative  position  of 
the  chalk  and  overlying  tertiary  deposits  ;  by  the  nature,  character, 
and  position  of  the  tertiary  strata ;  and  by  the  overlying  alluvia  of 
the  Weald  and  adjacent  countries.  As  to  the  superficial  detritus,  its 
insignificance  in  volume,  when  compared  to  the  missing  rocks,  should 
never  be  lost  sight  of.  A  mountain-mass  of  solid  matter,  hundreds 
of  square  miles  in  extent,  and  hundreds  of  yards  in  thickness,  has 
been  carried  away  bodily.  To  what  distance  it  has  been  transported 
we  know  not,  but  certainly  beyond  the  limits  of  the  Weald.  For 
achieving  such  a  task,  if  we  are  to  judge  by  analogy,  all  transient 
and  sudden  agency  is  hopelessly  inadequate.  There  is  one  power 
alone  which  is  competent  to  the  task,  namely,  the  mechanical  force 
of  water  in  motion,  operating  gradually,  and  for  ages.  We  have 
seen  in  the  6th  chapter  that  every  stratified  portion  of  the  earth's 
crust  is  a  monument  of  denudation  on  a  grand  scale,  always  effected 
slowly  ;  for  each  superimposed  stratum,  however  thin,  has  been  suc- 
cessively and  separately  elaborated.  Every  attempt,  therefore,  to 
circumscribe  the  time  in  which  any  great  amount  of  denudation, 
ancient  or  modern,  has  been  accomplished,  draws  with  it  the  gra- 
tuitous rejection  of  the  only  kind  of  machinery  known  to  us  which 
possesses  the  adequate  power. 

If,  then,  at  every  epoch,  from  the  Cambrian  to  the  Pliocene  inclu- 
sive, voluminous  masses  of  matter,  such  as  are  missing  in  the  Weald, 
have  been  transferred  from  place  to  place,  and  always  removed  gra- 
dually, it  seems  extravagant  to  imagine  an  exception  in  the  very 
region  where  we  can  prove  the  first  and  last  acts  of  denudation  to 
have  been  separated  by  so  vast  an  interval  of  time.  Here,  might  we 
say,  if  any  where  within  the  range  of  geological  enquiry,  we  have 
Hime  enough  and  without'  stint  at  our  command. 


U  2 


292  DIVISIONS   OF   THE   OOLITE.  [Cn.  XX. 


CHAPTER  XX. 

JUKASSIC    GROUP. PUEBECK   BEDS   AND   OOLITE. 

The  Purbeck  beds  a  member  of  the  Jurassic  group — Subdivisions  of  that  group — 
Physical  geography  of  the  Oolite  in  England  and  France — Upper  Oolite  — 
Purbeck  beds — New  fossil  Mammifer  found  at  Swanage  —  Dirt-bed  or  ancient 
soil — Fossils  of  the  Purbeck  beds  —  Portland  atone  and  fossils  —  Lithographic 
stone  of  Solenhofen — Middle  Oolite  —  Coral  rag  —  Zoophytes — Nerinasan  lime- 
stone—  Diceras  limestone  —  Oxford  clay,  Ammonites  and  Belemnites — Lower 
Oolite,  Crinoideans  —  Great  Oolite  and  Bradford  clay  —  Stonesfield  slate  — 
Fossil  mammalia,  placental  and  marsupial — Eesemblance  to  an  Australian 
fauna — Northamptonshire  slates — Yorkshire  Oolitic  coal-field — Brora  coal  — 
Fuller's  earth — Inferior  Oolite  and  fossils. 

IMMEDIATELY  below  the  Hastings  Sands  (the  inferior  member  of 
the  Wealden,  as  defined  in  the  18th  chapter),  we  find  in  Dorsetshire 
another  remarkable  freshwater  formation,  called  the  Purbeck^ 
because  it  was  first  studied  in  the  sea-cliffs  of  the  peninsula  of  Pur- 
beck in  Dorsetshire.  These  beds  were  formerly  grouped  with  the 
Wealden,  but  some  organic  remains  recently  discovered  in  certain 
intercalated  marine  beds  show  that  the  Purbeck  series  has  a  close 
affinity  to  the  Oolitic  group,  of  which  it  may  be  considered  as  the 
newest  or  uppermost  member. 

In  England  generally,  and  in  the  greater  part  of  Europe,  both  the 
Wealden  and  Purbeck  beds  are  wanting,  and  the  marine  cretaceous 
group  is  followed  immediately,  in  the  descending  order,  by  another 
series  called  the  Jurassic.  In  this  term,  the  formations  commonly 
designated  as  "  the  Oolite  and  Lias  "  are  included,  both  being  found 
in  the  Jura  Mountains.  The  Oolite  was  so  named  because  in  the 
countries  where  it  was  first  examined,  the  limestones  belonging  to  it 
had  an  oolitic  structure  (see  p.  12.).  These  rocks  occupy  in  Eng- 
land a  zone  which  is  nearly  30  miles  in  average  breadth,  and  extends 
across  the  island,  from  Yorkshire  in  the  north-east,  to  Dorsetshire 
in  the  south-west.  Their  mineral  characters  are  not  uniform 
throughout  this  region;  but  the  following  are  the  names  of  the 
principal  subdivisions  observed  in  the  central  and  south-eastern 
parts  of  England : — 

OOLITE. 

{a.  Purbeck  beds. 
b.  Portland  stone  and  sand, 
c.  Kimmeridge  clay. 


["/.   Cornbrash  and  Forest  marble. 
T  a.  Great  Oolite  and  Stonesfield  slate. 

Lower  1  1  Fuller's  earth. 

[i.  Inferior  Oolite. 
The  Lias  then  succeeds  to  the  Inferior  Oolite. 


CH.  XX.]          PHYSICAL   GEOGRAPHY  OF   THE   OOLITE. 


293 


The  Upper  oolitic  system  of  the  above  table  has  usually  the  Kim- 
meridge  clay  for  its  base ;  the  Middle  oolitic  system,  the  Oxford 
clay.  The  Lpwer  system  reposes  on  the  Lias,  an  argillo-calcareous 
formation,  which  some  include  in  the  Lower  Oolite,  but  which  will 
be  treated  of  separately  in  the  next  chapter.  Many  of  these  sub- 
divisions are  distinguished  by  peculiar  organic  remains  ;  and,  though 
varying  in  thickness,  may  be  traced  in  certain  directions  for  great 
distances,  especially  if  we  compare  the  part  of  England  to  which  the 
above-mentioned  type  refers  with  the  north-east  of  France  and  the 
Jura  mountains  adjoining.  In  that  country,  distant  above  400  geo- 
graphical miles,  the  analogy  to  the  accepted  English  type,  notwith- 
standing the  thinness  or  occasional  absence  of  the  clays,  is  more 
perfect  than  in  Yorkshire  or  Normandy. 

Physical  geography.  —  The  alternation,  on  a  grand  scale,  of  distinct 
formations  of  clay  and  limestone  has  caused  the  oolitic  and  liassic 
series  to  give  rise  to  some  marked  features  in  the  physical  outline  of 
parts  of  England  and  France.  Wide  valleys  can  usually  be  traced 
throughout  the  long  bands  of  country  where  the  argillaceous  strata 
crop  out ;  and  between  these  valleys  the  limestones  are  observed, 
composing  ranges  of  hills  or  more  elevated  grounds.  These  ranges 
terminate  abruptly  on  the  ^ide  on  which  the  several  clays  rise  up 
from  beneath  the  calcareous  strata. 

The  annexed  cut  will  give  the  reader  an  idea  of  the  configuration 
of  the  surface  now  alluded  to,  such  as  may  be  seen  in  passing  from 
London  to  Cheltenham,  or  in  other  parallel  lines,  from  east  to  west, 
in  the  southern  part  of  England.  It  has  been  necessary,  however, 


Lower 
Oolite. 


Fig.  333. 

Middle 

Oolite. 


Oolite. 


London 
Chalk,    clay. 


in  this  drawing,  greatly  to  exaggerate  the  inclination  of  the  beds, 
and  the  height  of  the  several  formations,  as  compared  to  their 
horizontal  extent.  It  will  be  remarked,  that  the  lines  of  cliff,  or 
escarpment,  face  towards  the  west  in  the  great  calcareous  eminences 
formed  by  the  Chalk  and  the  Upper,  Middle,  and  Lower  Oolites ; 
and  at  the  base  of  which  we  have  respectively  the  Gault,  Kim- 
meridge  clay,  Oxford  clay,  and  Lias.  This  last  forms,  generally,  a 
broad  vale  at  the  foot  of  the  escarpment  of  inferior  oolite,  but  where 
it  acquires  considerable  thickness,  and  contains  solid  beds  of  marl- 
stone,  it  occupies  the  lower  part  of  the  escarpment. 

The  external  outline  of  the  country  which  the  geologist  observes 
in  travelling  eastward  from  Paris  to  Metz  is  precisely  analogous,  and 
is  caused  by  a  similar  succession  of  rocks  intervening  between  the 
tertiary  strata  and  the  Lias  ;  with  this  difference,  however,  that  the 
escarpments  of  Chalk,  Upper,  Middle,  and  Lower  Oolites  face 
towards  the  east  instead  of  the  west. 

u  3 


294 


UPPER   PURBECK. 


[Cn.  XX. 


The  Chalk  crops  out  from  beneath  the  tertiary  sands  and  clays  of 
the  Paris  basin,  near  Epernay,  and  the  Gault  from  beneath  the 
Chalk  and  Upper  Greensand  at  Clermont-en-Argonne  ;  and  passing 
from  this  place  by  Verdun  and  Etain  to  Metz,  we  find  two  limestone 
ranges,  with  intervening  vales  of  clay,  precisely  resembling  those  of 
southern  and  central  England,  until  we  reach  the  great  plain  of  Lias 
at  the  base  of  the  Inferior  Oolite  at  Metz. 

It  is  evident,  therefore,  that  the  denuding  causes  have  acted  simi- 
larly over  an  area  several  hundred  miles  in  diameter,  sweeping  away 
the  softer  clays  more  extensively  than  the  limestones,  and  under- 
mining these  last  so  as  to  cause  them  to  form  steep  cliffs  wherever 
the  harder  calcareous  rock  was  based  upon  a  more  yielding  and 
destructible  clay. 

UPPER  OOLITE. 

Purbeck  beds  (a.  Tab.  p.  292.). —  These  strata,  which  we  class  as  the 
uppermost  member  of  the  Oolite,  are  of  limited  geographical  extent 
in  Europe,  as  already  stated,  but  they  acquire  importance,  when  we 
consider  the  succession  of  three  distinct  sets  of  fossil  remains  which 
they  contain.  Such  repeated  changes  in  organic  life  must  have  re- 
ference to  the  history  of  a  vast  lapse  of  ages.  The  Purbeck  beds 
are  finely  exposed  to  view  in  Durdlestone  Bay,  near  Swanage,  Dor- 
setshire, and  at  Lulworth  Cove  and  the  neighbouring  bays  between 
Weymouth  and  Swanage.  At  Meup's  Bay,  in  particular,  Prof.  E. 
Forbes  examined  minutely  in  1850  the  organic  remains  of  this 
group,  displayed  in  a  continuous,  sea-cliff  section ;  and  he  added 
largely  to  the  information  previously  supplied  in  the  works  of 
Messrs.  Webster,  Fitton,  De  la  Beche,  Buckland,  and  Mantell.  It 
appears  from  these  researches  that  the  Upper,  Middle,  and  Lower  Pur- 
becks  are  each  marked  by  peculiar  species  of  organic  remains,  these 
again  being  different,  so  far  as  a  comparison  has  yet  been  instituted, 
from  the  fossils  of  the  overlying  Hastings  Sands  and  Weald  Clay.* 

Upper  Purbeck.  —  The  highest  of  the  three  divisions  is  purely 
freshwater,  the  strata,  about  50  feet  in  thickness,  containing  shells 
of  the  genera  Paludina,  Physa,  Limnceus,  Planorbis,  Valvata,  Cyclas, 
and  Unio,  with  Cyprides  and  fish.  All  the  species  seem  peculiar, 
and  among  these  the  Cyprides  are  very  abundant  and  characteristic. 
(See  figs.  334.  «,  b,  c.) 


Cyprides  from  the  Upper  Purbecks. 
Cypris  gibbosa,  E.  Forbes,      b.  Cypris  tuberculata,  E.  Forbes,      c.  Cyprfs  leguminella,  E.  Forbes. 

*  «  On  the  Dorsetshire  Purbecks,"  by  Prof.  E.  Forbes,  Brit.  Assoc.  Edinb.  1850. 


CH.  XX.] 


MIDDLE   PURBECK. 


295 


The  stone  called  "Purbeck  marble,"  formerly  much  used  in 
ornamental  architecture  in  the  old  English  cathedrals  of  the 
southern  counties,  is  exclusively  procured  from  this  division. 

Middle  Purbeck. — Next  in  succession  is  the  Middle  Purbeck, 
about  30  feet  thick,  the  uppermost  part  of  which  consists  of  fresh- 
water limestone,  with  cyprides,  turtles,  and  fish,  of  different  species 
from  those  in  the  preceding  strata.  Below  the  limestone  are 
brackish-water  beds  full  of  Cyrena,  and  traversed  by  bands  abound- 
ing in  Corbula  and  Melania.  These  are  based  on  a  purely  marine 
deposit,  with  Pecten,  Modiola,  Avicula,  Thracia,  all  undescribed 
shells.  Below  this,  again,  come  limestones  and  shales,  partly  of 
brackish  and  partly  of  freshwater  origin,  in  which  many  fish, 
especially  species  of  Lepidotus  and  Microdon  radiatus,  are  found, 
and  a  crocodilian  reptile  named  Macrorhyncus.  Among  the  mol- 
lusks,  a  remarkable  ribbed  Melania,  of  the  section  Chilira,  occurs. 

Immediately  below  is  the  great  and  conspicuous  stratum,  12  feet 
thick,  long  familiar  to  geologists  under  the  local  name  of  "  Cinder- 
bed,"  formed  of  a  vast  accumulation  of  shells  of  Ostrea  distorta 
(fig.  335.).  In  the  uppermost  part  of  this  bed  Prof.  Forbes  dis- 
covered the  first  echinoderm  (fig.  336.)  as  yet  known  in  the  Purbeck 
series,  a  species  of  Hemicidaris,  a  genus  characteristic  of  the  Oolitic 
period,  and  scarcely,  if  at  all,  distinguishable  from  a  previously 
known  oolitic  species.  It  was  accompanied  by  a  species  of  Perna. 


Fig.  335. 


Fig.  336. 


Ostrea  dislorta. 
Cinder-bed,  Middle  Purbeck. 


Hemicidaris  Purheckensis,  E.  Forbes. 
Middle  Purbeck. 


Below  the  Cinder-bed  freshwater  strata  are  again  seen,  filled  in 
many  places  with  species  of  Cypris  (fig.  337.  a,  b,  c\  and  with  Valvata, 


Fig.  337. 


Cyprides  from  the  Middle  Purbecks. 
a.  Cypris  striato-punclata,  E.  Forbes,    b.  Cypris  fasciculata,  E.  Forbes,     c.  Cypris  granulala.  Sow. 

Paludina,  Planorbis,  Limn<zus,  Physa  (fig.   338.),  and  Cyclas,  all 
different  from  any  occurring  higher  in  the  series.     It  will  be  seen 

u  4 


296  FOSSILS  or  THE     IDDLE  PURBECK.         [CH.  xx. 

Fig.  338.  that  Cypris  fasciculata  (fig.  337.  b)  has  tubercles  at 
the  end  only  of  each  valve,  a  character  by  which  it 
can  be  immediately  recognized.  In  fact,  these  minute 
crustaceans,  almost  as  frequent  in  some  of  the  shales 
as  plates  of  mica  in  a  micaceous  sandstone,  enable 
geologists  at  once  to  identify  the  Middle  Purbeck  in 
Physa  Bristovii,  places  far  from  the  Dorsetshire  cliffs,  as  for  example, 
E'  FpurbeckMiddle  in  the  Vale  of  Wardour,  in  Wiltshire.  Thick  siliceous 
beds  of  chert  occur  in  the  Middle  Purbeck  filled 
with  mollusca  and  cyprides  of  the  genera  already  enumerated,  in  a 
beautiful  state  of  preservation,  often  converted  into  chalcedony. 
Among  these  Prof.  Forbes  met  with  gyrogonites  (the  spore  vessels 
of  CharcB\  plants  never  until  1851  discovered  in  rocks  older  than 
Eocene.  In  a  bed  of  this  series,  about  20  feet  below  the  "  Cinder," 
Mr.  W.  E.  Brodie  has  lately  found  (1854),  in  Durdlestone  Bay, 
portions  of  several  small  jaws  with  teeth,  which  Prof.  Owen,  after 
clearing  away  the  matrix,  recognized  as  belonging  to  a  small  mam- 
mifer  of  the  insectivorous  class.  The  teeth  with  pointed  cusps 
resemble  in  some  degree  those  of  the  Cape  Mole  (ChrysocTilora 
aured) ;  but  the  number  of  the  molar  teeth  (at  least  ten  in  each 
ramus  of  the  lower  jaw)  accords  with  that  in  the  extinct  Thylaco- 
therium of  the  Stonesfield  Oolite  (see  below,  Chap.  XX.).  This 
newly  found  quadruped,  therefore,  seems  to  have  been  more  closely 
allied  in  its  dentition  to  the  Thylacotherium  than  to  any  existing 
insectivorous  type.  As  in  Thylacotherium,  the  angular  process  of 
the  jaw  is  not  bent  inwards,  an  osteological  peculiarity  confined  to 
the  marsupial  tribes  (see  Chap.  XX.),  and  Prof.  Owen  therefore 
refers  the  Spalacotherium  to  the  placental  or  ordinary  class  of 
monodelphous  mammalia. 

In  a  former  edition  of  this  work  (1852),  after  alluding  to  the 
discovery  of  numerous  insects  and  air-breathing  mollusca  in  the 
"  Purbeck,"  I  remarked  that,  although  no  mammalia  had  then  been 
found,  "  it  was  too  soon  to  infer  their  non-existence  on  mere  nega- 
tive evidence."  The  scarcity  of  the  remains  of  warm-blooded 
quadrupeds  in  Oolitic  rocks,  and  the  fact  of  none  having  yet  been 
met  with  in  deposits  of  the  Cretaceous  era,  may  imply  that  there 
were  few  mammalia  then  living,  and  their  limited  numbers  may 
possibly  have  some  connection  with  the  enormous  development  of 
reptile  life  in  all  Secondary  periods,  as  compared  to  Tertiary  or 
Recent  times.  If  so,  the  phenomenon  has  at  least  no  relation  to  an 
incipient  or  immature  condition  of  the  planet,  as  some  have  imagined, 
for,  so  far  from  being  characteristic  of  primary  or  even  older  secondary 
times,  it  belongs  to  the  Maestricht  chalk,  the  newest  subdivision  of  the 
cretaceous  series,  and  that  too  in  a  manner  even  more  marked  than 
in  the  older  oolitic  rocks.  Nevertheless  in  the  present  imperfect 
state  of  our  information  respecting  the  land-animals  of  the  Cretaceous 
and  Jurassic  periods,  exclusively  derived  from  marine  and  flaviatile 
strata,  and  our  total  ignorance  of  the  deposits  formed  in  lakes  and 


CH.  XX.] 


LOWER   PURBECK. 


297 


Cypriotes  from  the  Lower  Purbecks. 
a.  Cypris  Purbeckensis,          b.  Cypri*  punctata, 
E.  Forbes. 


caverns   at   the   same  date,  it  would  be  premature  to  attempt  to 
generalize  on  the  nature  of  so  ancient  a  terrestrial  fauna. 

Beneath  the  freshwater  strata  last  described,  a  very  thin  band  of 
greenish  shales,  with  marine  shells  and  impressions  of  leaves,  like 
those  of  a  large  Zostera,  succeeds,  forming  the  base  of  the  Middle 
Purbeck. 

Lower  Purbeck.  —  Beneath  the  thin  marine  band  above  men- 
tioned, purely  freshwater  marls  occur,  containing  species  of  Cypris 

(fig.  339.  «,  b),  Valvata,  and 
Limnceus,  different  from  those 
of  the  Middle  Purbeck.  This 
is  the  beginning  of  the  inferior 
division,  which  is  about  80  feet 
thick.  Below  the  marls  are  seen 
more  than  30  feet  of  brackish- 
water  beds,  at  Meup's  Bay, 

E.Forbes.  "E.Forbes.     '    abounding  in  a  species  of  Ser- 

pula,  allied  to,  if  not  identical  with,  Serpula  coacervites,  found 
in  beds  of  the  same  age  in  Hanover.  There  are  also  shells  of 
the  genus  Rissoa  (of  the  subgenus  Hydrobia\  and  a  little  Cardium 
of  the  subgenus  Protocardium,  in  the  same  beds,  together  with 
Cypris.  Some  of  the  cypris-bearing  shales  are  strangely  contorted 
and  broken  up,  at  the  west  end  of  the  Isle  of  Purbeck.  The  great 
dirt-bed  or  vegetable  soil  containing  the  roots  and  stools  of  Cycadece, 
which  I  shall  presently  describe,  underlies  these  marls,  and  rests 
upon  the  lowest  freshwater  limestone,  a  rock  about  8  feet  thick, 
containing  Cyclas,  Valvata,  and  Limnceus,  of  the  same  species  as 
those  of  the  uppermost  part  of  the  Lower  Purbeck,  or  above  the 
dirt-bed.  The  freshwater  limestone  in  its  turn  rests  upon  the  top 
beds  of  the  Portland  stone,  which,  although  it  contains  purely 
marine  remains,  often  consists  of  a  rock  quite  homogeneous  in 
mineral  character  with  the  Lowest  Purbeck  limestone.* 

The  most  remarkable  of  all  the  varied  succession  of  beds  enu- 
merated in  the  above  list,  is  that  called  by  the  quarrymen  "the 

dirt,"  or  "black  dirt,"  which  was 


Fig.  340. 


Cycadeoidea  (Mantellia)  megalophylla,  Buckland. 


evidently  an  ancient  vegetable 
soil.  It  is  from  12  to  18  inches 
thick,  is  of  a  dark  brown  or  black 
colour,  and  contains  a  large  pro- 
portion of  earthy  lignite.  Through 
it  are  dispersed  rounded  frag- 
ments of  stone,  from  3  to  9  inches 
in  diameter,  in  such  numbers  that 
it  almost  deserves  the  name  of 
gravel.  Many  silicified  trunks 
of  coniferous  trees,  and  the  re- 


*  Weston,  Geol.  Q.  J.,  volviii.  p.  117. 


298  FOSSIL   FORESTS   IN   ISLE   OF   PORTLAND  [Cn.  XX. 

mains  of  plants  allied  to  Zamia  and  Cycas,  are  buried  in  this  dirt- 
bed  (see  figure  of  fossil  species,  fig.  340.,  and  of  living  Zamia,  fig. 
341.) 

Fig.  341. 


Zamia  spiralis.    Southern  Australia. 

These  plants  must  have  become  fossil  on  the  spots  where  they 
grew.  The  stumps  of  the  trees  stand  erect  for  a  height  of  from 
1  to  3  feet,  and  even  in  one  instance  to  6  feet,  with  their 
roots  attached  to  the  soil  at  about  the  same  distances  from  one 
another  as  the  trees  in  a  modern  forest.*  The  carbonaceous  matter 
is  most  abundant  immediately  around  the  stumps,  and  round  the 
remains  of  fossil  Cycadece.\ 

Besides  the  upright  stumps  above  mentioned,  the  dirt-bed  contains 
the  stems  of  silicified  trees  laid  prostrate.  These  are  partly  sunk 
into  the  black  earth,  and  partly  enveloped  by  a  calcareous  slate 
which  covers  the  dirt-bed.  The  fragments  of  the  prostrate  trees  are 
rarely  more  than  3  or  4  feet  in  length ;  but  by  joining  many  of 
them  together,  trunks  have  been  restored,  having  a  length  from  the 
root  to  the  branches  of  from  20  to  23  feet,  the  stems  being  undivided 
for  17  or  20  feet,  and  then  forked.  The  diameter  of  these  near  the 
roots  is  about  1  foot.  Root-shaped  cavities  were  observed  by 
Professor  Henslow  to  descend  from  the  bottom  of  the  dirt-bed  into 
the  subjacent  freshwater  stone,  which,  though  now  solid,  must  have 
been  in  a  soft  and  penetrable  state  when  the  trees  grew.  \ 

Fig.  342. 


freshwater  calcareous  slate. 


dirt-bed  and  ancient  forest. 

lowest  freshwater  beds  of  the  Lower 
Purbeck. 

„„,„.  ,  Portland  stone,  marine. 

Section  in  Isle  of  Portland,  Dorset.    (Buckland  and  De  la  Beche.) 

*  Mr.  Webster  first  noticed  the  erect  Trans.,  Second  Series,  vol.  iv.  p.  16. 

position  of  the  trees  and  described  the  Prof.  Forbes  has  ascertained  that  the 

Dirt-bed.  subjacent  rock  is  a  freshwater  limestone, 

f  Fitton,  Geol.  Trans.,  Second  Series,  and  not  a  portion  of  the  Portland  oolite, 

vol.  iv.  pp.  220,  221.  as  was  previously  imagined. 

|  Buckland  and  De  la  Beche,  GeoL 


CH.  XX.] 


AND   LUL WORTH   COVE. 


299 


The  thin  layers  of  calcareous  slate  (fig.  342.)  were  evidently  de- 
posited tranquilly,  and  would  have  been  horizontal  but  for  the  pro- 
trusion of  the  stumps  of  the  trees,  around  the  top  of  each  of  which 
they  form  hemispherical  concretions. 

The  dirt-bed  is  by  no  means  confined  to  the  island  of  Portland, 
where  it  has  been  most  carefully  studied,  but  is  seen  in  the  same 
relative  position  in  the  cliffs  east  of  Lulworth  Cove,  in  Dorsetshire, 
where,  as  the  strata  have  been  disturbed,  and  are  now  inclined  at  an 
angle  of  45°,  the  stumps  of  the  trees  are  also  inclined  at  the  same 
angle  in  an  opposite  direction  —  a  beautiful  illustration  of  a  change 
in  the  position  of  beds  originally  horizontal  (see  fig.  343.).  Traces 

Fig.  343. 

__ freshwater  calcareous  slate. 

dirt-bed,  with  stools  of  trees. 


freshwater. 


Portland  stone,  marine. 


Section  in  cliff  east  of  Lulworth  Cove.    (Bucklaud  and  De  la  Beche.) 

of  the  dirt-bed  have  also  been  observed  by  Mr.  Fisher,  at  Ridgway ; 
by  Dr.  Buckland,  about  two  miles  north  of  Thame,  in  Oxfordshire  ; 
and  by  Dr.  Fitton,  in  the  cliffs  in  the  Boulonnois,  on  the  French 
coast;  but,  as  might  be  expected,  this  freshwater  deposit  is  of 
limited  extent  when  compared  to  most  marine  formations. 

From  the  facts  above  described,  we  may  infer,  first,  that  those 
beds  of  the  upper  Oolite,  called  "  the  Portland,"  which  are  full  of 
marine  shells,  were  overspread  with  fluviatile  mud,  which  became 
dry  land,  and  covered  by  a  forest,  throughout  a  portion  of  the  space 
now  occupied  by  the  south  of  England,  the  climate  being  such  as  to 
admit  the  growth  of  the  Zamia  and  Cycas.  2dly.  This  land  at 
length  sank  down  and  was  submerged  with  its  forests  beneath  a 
body  of  fresh  water,  from  which  sediment  was  thrown  down  enve- 
loping fluviatile  shells.  3dly.  The  regular  and  uniform  preservation 
of  this  thin  bed  of  black  earth  over  a  distance  of  many  miles,  shows 
that  the  change  from  dry  land  to  the  state  of  a  freshwater  lake  or 
estuary,  was  not  accompanied  by  any  violent  denudation,  or  rush  of 
water,  since  the  loose  black  earth,  together  with  the  trees  which  lay 
prostrate  on  its  surface,  must  inevitably  have  been  swept  away  had 
any  such  violent  catastrophe  taken  place. 

The  dirt-bed  has  been  described  above  in  its  most  simple  form, 
but  in  some  sections  the  appearances  are  more  complicated.  The 
forest  of  the  dirt-bed  was  not  everywhere  the  first  vegetation  which 
grew  in  this  region.  Two  other  beds  of  carbonaceous  clay,  one  of 
them  containing  Cycadece,  in  an  upright  position,  have  been  found 
below  it,  and  one  above  it,  which  implies  other  oscillations  in  the 


300 


CHANGES   OF   MEDIUM.  —  PUEBECK   BEDS.         [Cn.  XX. 


level  of  the  same  ground,  and  its  alternate  occupation  by  land  and 
water  more  than  once. 

Table  showing  the  changes  of  medium  in  which  the  strata  were 
formed,  from  the  Portland  Stone  up  to  the  Lower  Greensand  in- 
clusive, in  the  south-east  of  England  (beginning  with  the  lowest). 


1.  Marine 

2.  Freshwater 
Land 

Freshwater 
Land 

Freshwater 
Land  (Dirt-bed) 
Freshwater 
Land 
Brackish 
Freshwater 


Portland  Stone. 


Lower  Purbeck. 


3.  Marine       1 
Freshwater 
Marine 

Brackish      }>  Middle  Purbeck. 

Marine 

Brackish 

FreshwaterJ 

4.  Freshwater    Upper  Purbeck. 

5.  Freshwater"! 

Brackish      >  Hastings  Sands. 
FreshwaterJ 

6.  Freshwater    Wealden  Clay. 

7.  Marine  Lower  Greensand. 


The  annexed  tabular  view  will  enable  the  reader  to  take  in  at  a 
glance  the  successive  changes  from  sea  to  river,  and  from  river  to 
sea,  or  from  these  again  to  a  state  of  land,  which  have  occurred  in 
this  part  of  England  between  the  Oolitic  and  Cretaceous  periods. 
That  there  have  been  at  least  four  changes  in  the  species  of  testacea 
during  the  deposition  of  the  Wealden  and  Purbeck  beds,  seems  to 
follow  from  the  observations  recently  made  by  Prof.  Forbes,  so  that, 
should  we  hereafter  find  the  signs  of  many  more  alternate  occupations 
of  the  same  area  by  different  elements,  it  is  no  more  than  we  might 
expect.  Even  during  a  small  part  of  a  zoological  period,  not  suffi- 
cient to  allow  time  for  many  species  t6  die  out,  we  find  that  the 
same  area  has  been  laid  dry,  and  then  submerged,  and  then  again 
laid  dry,  as  in  the  deltas  of  the  Po  and  Ganges,  the  history  of  which 
has  been  brought  to  light  by  Artesian  borings.*  We  also  know  that 
similar  revolutions  have  occurred  within  the  present  century  (1819) 
in  the  delta  of  the  Indus  in  Cutchf,  where  land  has  been  laid  perma- 
nently under  the  waters  both  of  the  river  and  sea,  without  its  soil 
or  shrubs  having  been  swept  away.  Even,  independently  of  any 
vertical  movements  of  the  ground,  we  see  in  the  principal  deltas,  such 
as  that  of  the  Mississippi,  that  the  sea  extends  its  salt  waters 
annually  for  many  months  over  considerable  spaces  which,  at  other 
seasons,  are  occupied  by  the  river  during  its  inundations. 

It  will  be  observed  that  the  division  of  the  Purbecks  into  upper, 
middle,  and  lower  has  been  made  by  Prof.  Forbes,  strictly  on  the 
principle  of  the  entire  distinctness  of  the  species  of  organic  remains 
which  they  include.  The  lines  of  demarcation  are  not  lines  of  dis- 
turbance, nor  indicated  by  any  striking  physical  characters  or  mineral 
changes.  The  features  which  attract  the  eye  in  the  Purbecks,  such 
as  the  dirt-beds,  the  dislocated  strata  at  Lulworth,  and  the  Cinder- 


*  See    Principles  of   Geol.   9th   ed. 
pp.  255.  275. 


•j-  Ibid.  p.  460. 


CH.  XX.]  PORTLAND   STONE.  301 

bed,  do  not  indicate  any  breaks  in  the  distribution  of  organized 
beings.  "  The  causes  which  led  to  a  complete  change  of  life  three 
times  during  the  deposition  of  the  freshwater  and  brackish  strata 
must,"  says  this  naturalist,  "be  sought  for,  not  simply  in  either  a 
rapid  or  a  sudden  change  of  their  area  into  land  or  sea,  but  in  the 
great  lapse  of  time  which  intervened  between  the  epochs  of  deposition 
at  certain  periods  during  their  formation." 

Each  dirt-bed  may,  no  doubt,  be  the  memorial  of  many  thousand 
years  or  centuries,  because  we  find  that  2  or  3  feet  of  vegetable  soil 
is  the  only  monument  which  many  a  tropical  forest  has  left  of  its 
existence  ever  since  the  ground  on  which  it  now  stands  was  first 
covered  with  its  shade.  Yet,  even  if  we  imagine  the  fossil  soils  of 
the  Lower  Purbeck  to  represent  as  many  ages,  we  need  not  expect 
on  that  account  to  find  them  constituting  the  lines  of  separation 
between  successive  strata  characterized  by  different  zoological  types. 
The  preservation  of  a  layer  of  vegetable  soil,  when  in  the  act  of  being 
submerged,  must  be  regarded  as  a  rare  exception  to  a  general  rule. 
It  is  of  so  perishable  a  nature,  that  it  must  usually  be  carried  away 
by  the  denuding  waves  or  currents  of  the  sea  or  by  a  river ;  and 
many  Purbeck  dirt-beds  were  probably  formed  in  succession,  and 
annihilated,  besides  those  few  which  now  remain. 

The  plants  of  the  Purbeck  beds,  so  far  as  our  knowledge  extends 
at  present,  consist  chiefly  of  Ferns,  Conifers  (fig.  344.),  and  Cycadeae 
Fig.  344.  (fig-  340.),  without  any  exogens  ;  the  whole  more 

allied  to  the  Oolitic  than  to  the  Cretaceous  vege- 
tation. The  vertebrate  and  invertebrate  animals 
indicate,  like  the  plants,  a  somewhat  nearer  rela- 
tionship to  the  Oolitic  than  to  the  cretaceous 
period.  Mr.  Brodie  has  found  the  remains  of 
beetles  and  several  insects  of  the  homopterous  and 
trichopterous  orders,  some  of  which  now  live  on 

Cane  of  a  pine  from  the     PlailtS>  whlle    °thei>S    ai>6  °f  SUCh.  formS    aS    h°V6r 

isle  of  Purbeck.  (Fitton.)    over  the  surface  of  our  present  rivers. 

Portland  Stone  and  Sand(b.  Tab.  p.  292.).—  The  Portland  stone  has 
already  been  mentioned  as  forming  in  Dorsetshire  the  foundation  on 
which  the  freshwater  limestone  of  the  Lower  Purbeck  reposes  (see 
p.  297.).  It  supplies  the  well-known  building-stone  of  which  St.  Paul's 
and  so  many  of  the  principal  edifices  of  London  are  constructed.  This 
upper  member  rests  on  a  dense  bed  of  sand,  called  the  Portland  sand, 
containing  for  the  most  part  similar  marine  fossils,  below  which  is 
the  Kimmeridge  clay.  In  England  these  Upper  Oolite  formations 
are  almost  wholly  confined  to  the  southern  counties.  Corals  are  rare 
in  them,  although  one  species  is  found  plentifully  at  Tisbury,  Wilt- 
shire, in  the  Portland  sand,  converted  into  flint  and  chert,  the  origi- 
nal calcareous  matter  being  replaced  by  silex  (fig.  345.). 

The  Kimmeridge  clay  consists,  in  great  part,  of  a  bituminous  shale, 
sometimes  forming  an  impure  coal,  several  hundred  feet  in  thickness. 
In  some  places  in  Wiltshire  it  much  resembles  peat ;  and  the  bitumi- 


302  FOSSILS   OF   THE   PORTLAND   STONE.  [Cn.  XX. 

Fig.  345. 


Fig.  346. 


Isastr&a  oblonga,  M.  Edw.  and  J.  Haime. 

As  seen  on  a  polished  slab  of  chert  from 

the  Portland  Sand,  Tisbury. 


Fig.  347. 


Trigonia  gibbosa.    %  nat.  size. 

a.  the  hinge. 
Portland  Stone,  Tisbury 


Fig.  348. 


Cardium  dissimile.    \  nat.  size. 
Portland  Stone. 


Ostrea  expansa. 
Portland  Sand. 


nous  matter  may  have  been,  in  part  at  least,  derived  from  the  decom- 
position of  vegetables.  But  as  impressions  of  plants  are  rare  in  these 
shales,  which  contain  ammonites,  oysters,  and  other  marine  shells,  the 
bitumen  may  perhaps  be  of  animal  origin. 

Among  the  characteristic  fossils  may  be  mentioned  Cardium  stria- 
tulum  (fig.  349.)  and  Ostrea  deltoidea  (fig.  350.),  the  latter  found  in 
the  Kimmeridge  clay  throughout  England  and  the  north  of  France, 
and  also  in  Scotland,  near  Brora.  The  Gryphcea  virgula  (fig.  351.), 


Fig.  350. 


Fig.  349. 


Cardium  striatulum. 
Kimmeridge  clay,  Hart  well. 


Ostrea  deltoidea.  Gryphcea  virgula. 

Upper  Oolite :  Kimmeridge  clay.    £  nat.  size. 


also  met  with  in  the  same  clay  near  Oxford,  is  so  abundant  in  the 
Upper  Oolite  of  parts  of  France  as  to  have  caused  the  deposit  to  be 
termed  "  marnes  a  gryphees  virgules."  Near  Clermont,  in  Argonne, 
a  few  leagues  from  St.  Menehould,  where  these  indurated  marls  crop 


CH.  XX.] 


CORAL   RAG. 


303 


Fig.  352. 


Trigonellites  latus. 
Kimmeridge  clay. 


out  from  beneath  the  gault,  I  have  seen  them,  on  decomposing,  leave 
the  surface  of  every  ploughed  field  literally  strewed  over  with  this 
fossil  oyster.  The  Trigonellites  latus  (Aptychus,  of  some  authors) 
(fig.  352.)  is  also  widely  dispersed  through  this 
clay.  The  real  nature  of  the  shell,  of  which  there 
are  many  species  in  oolitic  rocks,  is  still  a  matter 
of  conjecture.  Some  are  of  opinion  that  the  two 
plates  formed  the  gizzard  of  a  cephalopod ;  for 
the  living  Nautilus  has  a  gizzard  with  horny  folds, 
and  the  Bulla  is  well  known  to  possess  one  formed 
of  calcareous  plates. 
The  celebrated  lithographic  stone  of  Solenhofen,  in  Bavaria,  be- 
longs to  one  of  the  upper  divisions  of  the  oolite,  and  affords  a  re- 
markable example  of  the  variety  of  fossils  which  may  be  preserved 
under  favourable  circumstances,  and  what  delicate  impressions  of  the 
tender  parts  of  certain  animals  and  plants 
may  be  retained  where  the  sediment  is  of 
extreme  fineness.  Although  the  number  of 
testacea  in  this  slate  is  small,  and  the  plants 
few,  and  those  all  marine,  Count  Minister 
had  determined  no  less  than  237  species  of 
fossils  when  I  saw  his  collection  in  1833  ; 
and  among  them  no  less  than  seven  species 
of  flying  lizards,  or  pterodactyls  (see  fig. 
353.),  six  saurians,  three  tortoises,  sixty 
species  of  fish,  forty-six  of  Crustacea,  and 
twenty-six  of  insects.  These  insects, 
among  which  is  a  libellula,  or  dragon-fly, 
must  have  been  blown  out  to  sea,  probably 
from  the  same  land  to  which  the  flying 
lizards,  and  other  contemporaneous  rep- 
tiles, resorted. 


Fig.  353. 


Skeleton  of  Pterodactylus 

crassirostris. 

Oolite  of  Pappenheim,  near  Solen 
hofen. 


MIDDLE   OOLITE. 

Coral  Rag.  —  One  of  the  limestones  of  the  Middle  Oolite  has  been 
called  the  "  Coral  Rag,"  because  it  consists,  in  part,  of  continuous 
beds  of  petrified  corals,  for  the  most  part  retaining  the  position  in 
which  they  grew  at  the  bottom  of  the  sea.  In  their  forms  they  more 
frequently  resemble  the  reef-building  poliparia  of  the  Pacific  than  do 
the  corals  of  any  other  member  of  the  Oolite.  They  belong  chiefly 
to  the  genera  Thecosmilia  (fig.  354.),  Protoseris,  and  Thamnastrcea, 
and  sometimes  form  masses  of  coral  15  feet  thick.  In  the  annexed 
figure  of  a  Thamnastrcea  (fig.  355.),  from  this  formation,  it  will  be 
seen  that  the  cup-shaped  cavities  are  deepest  on  the  right-hand  side, 
and  that  they  grow  more  and  more  shallow,  until  those  on  the  left 
side  are  nearly  filled  up.  The  last-mentioned  stars  are  supposed  to 
represent  a  perfected  condition,  and  the  others  an  immature  state. 
These  coralline  strata  extend  through  the  calcareous  hills  of  the 


304 


COEALS   OF   THE   OOLITE. 

Corals  of  the  Coral  Rag. 


[CH.  XX. 


Fig.  354 


Fig.  355. 


Thecosmilia  annularis,  Milne  Edw.  and  J.  Haimc. 
Coral  Rag,  Steeple  Ashton. 


Thamnastraa. 
Coral  Rag,  Steeple  Ashton. 


N.  W.  of  Berkshire,  and  north  of  Wilts,  and  again  recur  in  York- 
shire, near  Scarborough.  The  Ostrea  gregarea  (fig.  356.)  is  very 
characteristic  of  the  formation  in  England  and  on  the  continent. 

One  of  the  limestones  of  the  Jura,  referred  to  the  age  of  the  English 
coral-rag,  has  been  called  "Nerinsean  limestone"  (Calcaire  a  Ne- 
rinees)  by  M.  Thirria ;  Nerincea  being  an  extinct  genus  of  univalve 
shells,  much  resembling  the  Cerithium  in  external  form.  The  an- 
nexed section  (fig.  357.)  shows  the  curious  form  of  the  hollow  part 
of  each  whorl,  and  also  the  perforation  which  passes  up  the  middle 
of  the  columella.  N.  Goodhallii  (fig.  358.)  is  another  English  species 


Fig.  357. 


Fig.  356. 


Fig.  358. 


Ostrea  gregarea.  Nertruea  hieroglyphica 

Coral  rag,  Steeple  Ashton.  Coral  rag. 


Nerin&a  Goodhrtllii,  Fitton. 
Coral  rag,  Weymouth.    £  nat.  size. 


of  the  same  genus,  from  a  formation  which  seems  to  form  a  passage 
from  the  Kimmeridge  clay  to  the  coral  rag.* 

A  division  of  the  oolite  in  the  Alps,  regarded  by  most  geologists 
as  coeval  with  the  English  coral  rag,  has  been  often  named  "  Calcaire 
a  Dicerates,"  or  "  Diceras  limestone,"  from  its  containing  abundantly 
a  bivalve  shell  (see  fig.  359.)  of  a  genus  allied  to  the  Chama. 


*  Fitton,  Geol.  Trans.,  Second  Series,  vol.  iv.  pi.  23.  fig.  12. 


Cu.  XX.]  FOSSILS   OP   THE   OXFORD   CLAY. 

Fig.  360. 


Fig.  359. 


305 


Cast  of  Diceras  arietina. 
Coral  rag,  France. 


Cidaris  coronata. 
Coral  rag. 


Oxford  Clay.  —  The  coralline  limestone,  or  "coral  rag,"  above 
described,  and  the  accompanying  sandy  beds,  called  "calcareous 
grits,"  of  the  Middle  Oolite,  rest  on  a  thick  bed  of  clay,  called  the 
"  Oxford  clay,"  sometimes  not  less  than  500  feet  thick.  In  this  there 
are  no  corals,  but  great  abundance  of  cephalopoda  of  the  genera 
Ammonite  and  Belemnite.  (See  figs.  361,  362.)  In  some  of  the  clay 

Fig.  361. 


Belemnites  kastatut.    Oxford  clay. 

of  very  fine  texture  ammonites  are  very  perfect,  although  somewhat 
compressed,  and  are  seen  to  be  furnished  on  each  side  of  the  aperture 
with  a  single  horn-like  projection  (see  fig.  362.).  These  were  dis- 
covered in  the  cuttings  of  the  Great  Western  Railway,  near  Chippen- 
ham,  in  1841,  and  have  been  described  by  Mr.  Pratt  (An.  Nat. 
Hist.  Nov.  1841). 

Fig.  362. 


Ammonites  Jason,  Reinecke.    Syn.  A.  Elizabeths,  Pratt. 
Oxford  clay,  Christian  Malford,  Wiltshire. 


306 


Fig.  363. 


Bdemnifes  Puzostanus, 

D'Orb. 
Oxford  Clay,  Christian 

Mai  ford. 

«,  a.  projecting  processes 
of  the  shell  or 
phragmocone. 

b,  c.  broken  exterior   of   a 

conical  shell  called 
the  phragmocone, 
which  is  chambered 
within,  or  composed 
of  a  series  of  shallow 
concave  cells  pierced 
by  a  siphuncle. 

c,  d.  The  guard  or  osselet, 

which  is  commonly 
called  the  belemnite. 


LOWER   OOLITE.  [Cn.  XX. 

Similar  elongated  processes  have  been 
also  observed  to  extend  from  the  shells  of 
some  belemnites  discovered  by  Dr.  Mantell 
in  the  same  clay  (see  fig.  363.),  who,  by  the 
aid  of  this  and  other  specimens,  has  been 
able  to  throw  much  light  on  the  structure 
of  this  singular  extinct  form  of  cuttle-fish.* 


LOWER  OOLITE. 

Cornbrash  and  Forest  Marble.  —  The 
upper  division  of  this  series,  which  is  more 
extensive  than  the  preceding  or  Middle 
Oolite,  is  called  in  England  the  Cornbrash. 
It  consists  of  clays  and  calcareous  sandstones, 
which  pass  downwards  into  the  Forest  mar- 
ble, an  argillaceous  limestone,  abounding  in 
marine  fossils.  In  some  places,  as  at  Brad- 
ford, this  limestone  is  replaced  by  a  mass 
of  clay.  The  sandstones  of  the  Forest  Mar- 
ble of  Wiltshire  are  often  ripple-marked  and 
filled  with  fragments  of  broken  shells  and 
pieces  of  drift-wood,  having  evidently  been 
formed  on  a  coast.  Rippled  slabs  of  fissile 
oolite  are  used  for  roofing,  and  have  been 
traced  over  a  broad  band  of  country  from 
Bradford,  in  Wilts,  to  Tetbury,  in  Glouces- 
tershire. These  calcareous  tile-stones  are 
separated  from  each  other  by  thin  seams  of 
clay,  which  have  been  deposited  upon  them, 
and  have  taken  their  form,  preserving  the 
undulating  ridges  and  furrows  of  the  sand 
in  such  complete  integrity,  that  the  impres- 
sions of  small  footsteps,  apparently  of  crabs, 
which  walked  over  the  soft  wet  sands,  are 
still  visible.  In  the  same  stone  the  claws 
of  crabs,  fragments  of  echini,  and  other 
signs  of  a  neighbouring  beach,  are  ob- 
served, f 

Great  Oolite.  —  Although  the  name  of 
coral-rag  has  been  appropriated,  as  we  have 
seen,  to  a  member  of  the  Upper  Oolite  be- 
fore described,  some  portions  of  the  Lower 
Oolite  are  equally  entitled  in  many  places 
to  be  called  coralline  limestones.  Thus  the 
Great  Oolite  near  Bath  contains  various 


*  See  Phil.  Trans.  1850,  p.  393. 

f  P.  Scrope,  Geol.  Proceed.,  March,  1831. 


CH.  XX.] 


BRADFORD   ENCRINITES. 

Fig.  364. 


307 


Eunomia  radiata,  Lamouroux.    (Calamophyllia,  Milne  Edw.) 

a.  section  transverse  to  the  tubes. 

b.  vertical  section,  showing  the  radiation  of  the  tubes. 

c.  portion  of  interior  of  tubes  magnified,  showing  striated  surface. 

corals,  among  which  the  Eunomia  radiata  (fig.  364.)  is  very  con- 
spicuous, single  individuals  forming  masses  several  feet  in  diameter ; 
and  having  probably  required,  like  the  large  existing  brain-coral 
(Meandrina)  of  the  tropics,  many  centuries  before  their  growth  was 
completed. 

Different  species  of  Crinoideans,  or  stone-lilies,  are  also  common 
in  the  same  rocks  with  corals ;  and,  like  them,  must  have  enjoyed  a 
firm  bottom,  where  their  root,  or  base  of  attachment,  remained  un- 
disturbed for  years  (c,  fig.  365.).  Such  fossils,  therefore,  are  almost 

Fig.  365. 


Apiocrinites  rolundus,  or  Pear  Encrinite ;  Miller.    Fossil  at  Bradford,  Wilts. 

a.  Stem  of  Apiocrinites,  and  one  of  the  articulations,  natural  size. 

b.  Section  at  Bradford  of  great  oolite  and  overlying  clay,  containing  the  fossil  encrinites.    See  text. 

c.  Three  perfect  individuals  of  Apiocrinites,  represented  as  they  grew  on  the  surface  of  the  Great 

Oolite. 

d.  Body  of  the  Apiocrinites  rotundus. 

confined  to  the  limestones ;  but  an  exception  occurs  at  Bradford,  near 
Bath,  where  they  are  enveloped  in  clay.  In  this  case,  however,  it 
appears  that  the  solid  upper  surface  of  the  "  Great  Oolite  "  had  sup- 
ported, for  a  time,  a  thick  submarine  forest  of  these  beautiful 
zoophytes,  until  the  clear  and  still  water  was  invaded  by  a  current 
charged  with  mud,  which  threw  down  the  stone-lilies,  and  broke 
most  of  their  stems  short  off  near  the  point  of  attachment.  The 
stumps  still  remain  in  their  original  position;  but  the  numerous 
articulations,  once  composing  the  stem,  arms,  and  body  of  the 
zoophyte,  were  scattered  at  random  through  the  argillaceous  deposit 

x  2 


308  BRADFORD   ENCRINITES.  [Cn.  XX. 

in  which  some  now  lie  prostrate.  These  appearances  are  represented 
in  the  section  £,  fig.  365.,  where  the  darker  strata  represent  the 
Bradford  clay,  which  some  geologists  class  with  the  Forest  marble, 
others  with  the  Great  Oolite.  The  upper  surface  of  the  calcareous 
stone  below  is  completely  incrusted  over  with  a  continuous  pavement, 
formed  by  the  stony  roots  or  attachments  of  the  Crinoidea;  and 
besides  this  evidence  of  the  length  of  time  they  had  lived  on  the 
spot,  we  find  great  numbers  of  single  joints,  or  circular  plates  of  the 
stem  and  body  of  the  encrinite,  covered  over  with  serpultz.  Now 
these  serpulcB  could  only  have  begun  to  grow  after  the  death  of  some 
of  the  stone-lilies,  parts  of  whose  skeletons  had  been  strewed  over 
the  floor  of  the  ocean  before  the  irruption  of  argillaceous  mud.  In 
some  instances  we  find  that,  after  the  parasitic  serpulce  were  full 
grown,  they  had  become  incrusted  over  with  a  bryozoan,  called 
Berenicea  diluviana ;  and  many  generations  of  these  molluscs  had 
succeeded  each  other  in  the  pure  water  before  they  became  fossil. 


Fig.  366. 


a.  Single  plate  or  articulation  of  an  Encrinite  overgrown  with  serpula  and  bryozoa.    Natural  size. 

b.  Portion  of  the  same  magnified,  showing  the  bryozoan  Berenicea  diluviana  covering  one  of  the 

serpuUe. 

We  may,  therefore,  perceive  distinctly  that,  as  the  pines  and  cyca- 
deous  plants  of  the  ancient  "  dirt-bed,"  or  fossil  forest,  of  the  Lower 
Purbeck  were  killed  by  submergence  under  fresh  water,  and  soon 
buried  beneath  muddy  sediment,  so  an  invasion  of  argillaceous 
matter  put  a  sudden  stop  to  the  growth  of  the  Bradford  Encrinites, 
and  led  to  their  preservation  in  marine  strata.* 

Such  differences  in  the  fossils  as  distinguish  the  calcareous  and 
argillaceous  deposits  from  each  other,  would  be  described  by  natu- 
ralists as  arising  out  of  a  difference  in  the  stations  of  species ;  but 
besides  these,  there  are  variations  in  the  fossils  of  the  higher,  middle, 
and  lower  part  of  the  oolitic  series,  which  must  be  ascribed  to  that 
great  law  of  change  in  organic  life  by  which  distinct  assemblages  of 
species  have  been  adapted,  at  successive  geological  periods,  *to  the 
varying  conditions  of  the  habitable  surface.  In  a  single  district  it  is 
difficult  to  decide  how  far  the  limitation  of  species  to  certain  minor 

*  For  a  fuller  account  of  these  Encrinites,  see  Buckland's  Bridgewater  Treatise, 
vol.  i.  p.  429. 


CH.  XX.] 


FOSSILS   OF   THE   GREAT   OOLITE. 


309 


formations  has  been  due  to  the  local  influence  of  stations,  or  how  far 
it  has  been  caused  by  time  or  the  creative  and  destroying  law  above 
alluded  to.  But  we  recognize  the  reality  of  the  last-mentioned  influ- 
ence, when  we  contrast  the  whole  oolitic  series  of  England  with  that 
of  parts  of  the  Jura,  Alps,  and  other  distant  regions,  where  there  is 
scarcely  any  lithological  resemblance ;  and  yet  some  of  the  same 
fossils  remain  peculiar  in  each  country  to  the  Upper,  Middle,  and1 
Lower  Oolite  formations  respectively.  Mr.  Thurmann  has  shown 
how  remarkably  this  fact  holds  true  in  the  Bernese  Jura,  although 
the  argillaceous  divisions,  so  conspicuous  in  England,  are  feebly  re- 
presented there,  and  some  entirely  wanting. 

The  Bradford  clay  above  alluded  to  is  sometimes  60  feet  thick, 
but,  in  many  places,  it  is  wanting ;  and,  in  others,  where  there  are 
no  limestones,  it  cannot  easily  be  separated  from  the  clays  of  the 
overlying  "  forest  marble "  and  underlying  "  fuller's  earth." 

The  calcareous  portion  of  the  Great  Oolite  consists  of  several 
shelly  limestones,  one  of  which,  called  the  Bath  Oolite,  is  much  cele- 
brated as  a  building -stone.  In  parts  of  Gloucestershire,  especially 
near  Minchinhampton,  the  Great  Oolite,  says  Mr.  Lycett,  "  must  have 
been  deposited  in  a  shallow  sea,  where  strong  currents  prevailed,  for 
there  are  frequent  changes  in  the  mineral  character  of  the  deposit, 
and  some  beds  exhibit  false  stratification.  In  others,  heaps  of  broken 
shells  are  mingled  with  pebbles  of  rocks  foreign  to  the  neighbour- 
hood, and  with  fragments  of  abraded  madrepores,  dicotyledonous 
wood,  and  crabs'  claws.  The  shelly  strata,  also,  have  occasionally 
suffered  denudation,  and  the  removed  portions  have  been  replaced  by 
clay."*  In  such  shallow-water  beds  shells  of  the  genera  Patella, 


Fig.  368 


Fig.  367 


Fig.  369. 


Terebratula  dfgona.  Purpuroidea  noflulata.    i  nat.  size.  Cylindrites  acutus,  Sow. 

Nat.  size.    Bradford  clay.          Great  Oolite  Minchinhampton.  Syn.  Actceon  arutus, 

Great  Oolite,  Minchinhamptc 


Fig.  372. 


Fig.  370. 


Fig  371. 


Patella  rugosa,  Sow. 
Great  Oolite. 


Nerita  costulata,  Desh.       Simula  (Ewarginula)  clatttrata,. 
Great  Oolite.  Sow.    Great  Oolite. 


*  Lycett,  Geol.  Journ.  vol.  iv.  p.  183. 
x  3 


310  STONESFIELD    SLATE.  [Cn.  XX. 

Nerita,  Rimula,  and  Cylindrites  are  common  (see  figs.  369.  to  372.) ; 
while  cephalopods  are  rare,  and,  instead  of  ammonites  and  belem- 
nites,  numerous  genera  of  carnivorous  trachelipods  appear.  Out  of 
one  hundred  and  forty-two  species  of  univalves  obtained  from  the 
Mmchinhampton  beds,  Mr.  Lycett  found  no  less  than  forty-one  to 
be  carnivorous.  They  belong  principally  to  the  genera  Buccinum, 
Pleurotoma,  Rostellaria,  Murex,  Purpuroidea  (fig.  368.),  and  Fusus, 
and  exhibit  a  proportion  of  zoophagous  species  not  very  different 
from  that  which  obtains  in  warm  seas  of  the  recent  period.  These 
chronological  results  are  curious  and  unexpected,  since  it  was 
imagined  that  we  might  look  in  vain  for  the  carnivorous  trachelipods 
in  rocks  of  such  high  antiquity  as  the  Great  Ooolite,  and  it  was  a 
received  doctrine  that  they  did  not  begin  to  appear  in  considerable 
numbers  till  the  Eocene  period,  when  those  two  great  families  of 
cephalopoda,  the  ammonites  and  belemnites,  had  become  extinct. 

Stonesfield  slate. — The  slate  of  Stonesfield  has  been  shown  by 
Mr.  Lonsdale  to  lie  at  the  base  of  the  Great  Oolite.  *  It  is  a  slightly 
oolitic  shelly  limestone,  forming  large  spheroidal  masses  imbedded  in 
sand,  only  6  feet  thick,  but  very  rich  in  organic  remains.  It  con- 
tains some  pebbles  of  a  rock  very  similar  to  itself,  and  which  may 
be  portions  of  the  deposit,  broken  up  on  a  shore  at  low  water  or 
during  storms,  and  redeposited.  The  remains  of  belemnites,  tri- 
goniae,  and  other  marine  shells,  with  fragments  of  wood,  are  common, 
and  impressions  of  ferns,  cycadese,  and  other  plants.  Several  insects, 
rig.  373.  also,  and,  among  the  rest,  the  wing-covers  of  beetles,  are 
perfectly  preserved  (see  fig.  373.),  some  of  them  approach- 
ing nearly  to  the  genus  Buprestis.^  The  remains,  also,  of 
many  genera  of  reptiles,  such  as  Pleiosaur,  Crocodile,  and 
Pterodactyl,  have  been  discovered  in  the  same  limestone. 

But  the  remarkable  fossils  for  which  the  Stonesfield 
slate  is  most  celebrated  are  those  referred  to  the  mam- 
miferous  class.  The  student  should  be  reminded  that  in 
all  the  rocks  described  in  the  preceding  chapters  as  older 
tnan  tne  Eocene,  no  bones  of  any  land  quadruped,  or  of 
Stonesfield.  any  cetacean,  had  been  discovered  until  the  Spalacothe- 
rium  of  the  Purbeck  beds  came  to  light  in  1854  (see  above,  p.  296.). 
Yet  we  have  seen  that  terrestrial  plants  were  not  rare  in  the  lower 
cretaceous  formation,  and  that  in  the  Wealden  there  was  evidence  of 
freshwater  sediment  on  a  large  scale,  containing  various  plants,  and 
even  ancient  vegetable  soils.  We  had  also  in  the  same  Wealden 
many  land-reptiles  and  winged  insects,  which  render  the  absence  of 
terrestrial  quadrupeds  the  more  striking.  The  want,  however,  of 
any  bones  of  whales,  seals,  dolphins,  and  other  aquatic  mammalia, 
whether  in  the  chalk  or  in  the  upper  or  middle  oolite,  is  certainly 
still  more  remarkable.  Formerly,  indeed,  a  bone  from  the  great 
oolite  of  Enstone,  near  Woodstock,  in  Oxfordshire,  was  cited,  on  the 

*  Proceedings  Geol.  Soc.  vol.i.  p.  41 4.    it  is  suggested  that  these  elytra  may 
f  See  Buckland's  Bridgewater  Trea-    belong  to  Priomus. 
tise ;  and  Brodie's  Fossil  Insects,  where 


CH.  XX.]  FOSSILS   OF    THE   OOLITE.  311 

authority  of  Cuvier,  as  referable  to  this  class.  Dr.  Buckland,  who 
stated  this  in  his  Bridgewater  Treatise  *,  had  the  kindness  to  send 
me  the  supposed  ulna  of  a  whale,  that  Prof.  Owen  might  examine 
into  its  claims  to  be  considered  as  cetacean.  It  is  the  opinion  of 
that  eminent  comparative  anatomist  that  it  cannot  have  belonged  to 
the  cetacea,  because  the  fore-arm  in  these  marine  mammalia  is  in- 
variably much  flatter,  and  devoid  of  all  muscular  depressions  and 
ridges,  one  of  which  is  so  prominent  in  the  middle  of  this  bone, 
represented  in  the  annexed  cut  (fig.  374.).  In  saurians,  on  the  con- 
Fig.  374. 


Bone  of  a  Reptile,  formerly  supposed  to  be  the  ulna  of  a  Cetacean  ;  from  the  Great  Oolite  of 
Enstone,  near  Woodstock. 

trary,  such  ridges  exist  for  the  attachment  of  muscles  ;  and  to  some 
animal  of  that  class  the  bone  is  probably  referable. 

These  observations  are  made  to  prepare  the  reader  to  appreciate 
more  justly  the  interest  felt  by  every  geologist  in  the  discovery  in 
the  Stonesfield  slate  of  no  less  than  seven  specimens  of  lower  jaws  of 
mammiferous  quadrupeds,  belonging  to  three  different  species  and  to 
two  distinct  genera,  for  which  the  names  of  Amphitherium  and  Phas- 
colotherium  have  been  adopted.  When  Cuvier  was  first  shown  one 
of  these  fossils  in  1818,  he  pronounced  it  to  belong  to  a  small  ferine 
mammal,  with  a  jaw  much  resembling  that  of  an  opossum,  but  differ- 
ing from  all  known  ferine  genera,  in  the  great  number  of  the  molar 
teeth,  of  which  it  had  at  least  ten  in  a  row.  Since  that  period,  a 
much  more  perfect  specimen  of  the  same  fossil,  obtained  by  Dr. 
Buckland  (see  fig.  375.),  has  been  examined  by  Prof.  Owen,  who 
finds  that  the  jaw  contained  on  the  whole  twelve  molar  teeth,  with 
the  socket  of  a  small  canine,  and  three  small  incisors,  which  are  in 
situ,  altogether  amounting  to  sixteen  teeth  on  each  side  of  the  lower 
jaw. 

The  only  question  which  could  be  raised  respecting  the  nature  of 
these  fossils  was,  whether  they  belonged  to  a  mammifer,  a  reptile,  or 
a  fish.  Now  on  this  head  the  osteologist  observes  that  each  of  the 
seven  half  jaws  is  composed  of  but  one  single  piece,  and  not  of  two  or 
more  separate  bones,  as  in  fishes  and  most  reptiles,  or  of  two  bones, 
united  by  a  suture,  as  in  some  few  species  belonging  to  those  classes., 

*  Vol.i.p.  115. 

X  4 


312 


OOLITIC   GROUP 

Fig.  375. 
Natural  size. 


[CH.  XX. 


Amphitherium  Broderipii,  Owen. 
Natural  size.  Stonesfield  Slate. 


Amphitherium  Prevostii,  CUT.  Sp.    Stonesfield  Slate. 
a.  coronold  process.  6.  condyle.  c.  angle  of  jaw.  d.  double-fanged  molars. 

Fig- 376.  The  condyle,   moreover    (b,  fig.  375.),  or 

articular  surface,  by  which  the  lower  jaw 
unites  with  the  upper,  is  convex  in  the 
Stonesfield  specimens,  and  not  concave  as 
in  fishes  and  reptiles.  The  coronoid  pro- 
cess (a,  fig.  375.)  is  well  developed,  whereas 

it  is  wanting  or  very  small,  in  the  inferior  classes  of  vertebrata. 
Lastly,  the  molar  teeth  in  the  Amphitherium  and  Phascolotherium 
have  complicated  crowns  and  two  roots  (see  d,  fig.  375.),  instead 
of  being  simple  and  with  single  fangs.* 

The  only  question,  therefore,  which  could  fairly  admit  of  contro- 
versy was  limited  to  this  point,  whether  the  fossil  mammalia  found 
in  the  lower  oolite  of  Oxfordshire  ought  to  be  referred  to  the  mar- 
supial quadrupeds,  or  to  the  ordinary  placental  series.  Cuvier  had 
long  ago  pointed  out  a  peculiarity  in  the  form  of  the  angular  process 
(c,  figs.  380.  and  381.)  of  the  lower  jaw,  as  a  character  of  the  genus 


Fig.  377. 


Tupaia  Tana. 
Right  ramus  of  lower  jaw. 

Natural  size. 

A  recent  insectivorous  mammal  from 
Sumatra. 


Fig.  378.  Fig.  379. 


Fig.  380. 


Fig.  381. 


Part  of  lower  jaw  of  Tupaia  Tana  ; 
twice  natural  size. 

Fig.  378.  End  view  seen  from  behind,  showing 

the  very  slight  inflection  of  the  angle  at  c. 
Fig.  379.  Side  view  of  same. 


Part  of  lower  jaw  of  Didelphys  Azarce; 
recent,  Brazil.    Natural  size. 

Fig.  380.  End  view  seen  from  behind,  showing 

the  inflection  of  the  angle  of  the  jaw,  c,  d. 
Fig.  381.  Side  view  of  same. 


*  I  have  given  a  figure  in  the  Prin-     Prevostii,  in  which  the  sockets  and  roots 
ciples  of  Geology,  chap,  ix.,  of  another    of  the  teeth  are  finely  exposed. 
Stonesfield  specimen   of  Amphitherium 


CH.  XX.]  %         AND   ITS   FOSSILS  313 

Didelphys  ;  and  Prof.  Owen  has  since  established  its  generality  in  the 
entire  marsupial  series.  In  all  these  pouched  quadrupeds,  this  pro- 
cess is  turned  inwards,  as  at  c  d}  fig.  380.  in  the  Brazilian  opossum, 
whereas  in  the  placental  series,  as  at  c,  figs.  378.  and  379.,  there  is  an 
almost  entire  absence  of  such  inflection.  The  Tupaia  Tana  of 
Sumatra  has  been  selected  by  my  friend  Mr.  Waterhouse  for  this 
illustration,  because  that  small  insectivorous  quadruped  bears  a  great 
resemblance  to  those  of  the  Stonesfield  Amphitherium.  By  clearing 
away  the  matrix  from  the  specimen  of  Amphitherium  Prevostii  above 
represented  (fig.  375.)  Prof.  Owen  ascertained  that  the  angular 
process  (c)  bent  inwards  in  a  slighter  degree  than  in  any  of  the 
known  marsupialia ;  in  short,  the  inflection  does  not  exceed  that  of 
the  mole  or  hedgehog.  This  fact  turns  the  scale  in  favour  of  its 
affinities  to  the  placental  insectivora.  Nevertheless,  the  Amphithe- 
rium offers  some  points  of  approximation  in  its  osteology  to  the 
marsupials,  especially  to  the  Myrmecobius,  a  small  insectivorous 
quadruped  of  Australia,  which  has  nine  molars  on  each  side  of  the 
lower  jaw,  besides  a  canine  and  three  incisors.* 

Another  species  of  Amphitherium  has  been  found  at  Stonesfield 
(fig.  376.  p.  312.),  which  differs  from  the  former  (fig.  375.)  princi- 
pally in  being  larger. 

The  second  mammiferous  genus  discovered  in  the  same  slates  was 
named  originally  by  Mr.  Broderip  Didelphys  Bucklandi  (see  fig.  382.), 

-     .\        Fig.  382. 


Phascolotherium  Bucklandi,  Broderip,  sp. 
a.  natural  size.  b.  molar  of  same  magnified. 

and  has  since  been  called  Phascolotherium  by  Owen.  It  manifests  a 
much  stronger  likeness  to  the  marsupials  in  the  general  form  of  the 
,'jaw,  and  in  the  extent  and  position  of  its  inflected  angle,  while  the 
agreement  with  the  living  genus  Didelphys  in  the  number  of  the 
premolar  and  molar  teeth  is  complete.f 

On  reviewing,  therefore,  the  whole  of  the  osteological  evidence,  it 
will  be  seen  that  we  have  every  reason  to  presume  that  the  Amphi- 
therium and  Phascolotherium  of  Stonesfield  represent  both  the  pla- 
cental and  marsupial  classes  of  mammalia ;  and  if  so,  they  warn  us  in 
a  most  emphatic  manner,  not  to  found  rash  generalizations  respecting 
the  non-existence  of  certain  classes  of  animals  at  particular  periods 
of  the  past  on  mere  negative  evidence.  The  singular  accident  of 
our  having  as  yet  found  nothing  but  the  lower  jaws  of  seven  indi- 
viduals, and  no  other  bones  of  their  skeletons,  is  alone  sufficient  ta 
demonstrate  the  fragmentary  manner  in  which  the  memorials  of  an 

*  A  figure  of  this  recent  Myrmecobius  f  Owen's  British  Fossil  Mammals, 
will  be  found  in  the  Principles,  chap.  ix.  p.  62. 


314  OOLITIC   GROUP  [CH.  XX. 

ancient  terrestrial  fauna  are  handed  down  to  us.     We  can  scarcely 
avoid  suspecting  that   the  two  genera  above  described  may  have 
borne  a  like  insignificant  proportion  to  the  entire  assemblage  of  warm- 
blooded quadrupeds  which  flourished  in  the  islands  of  the  oolitic  sea. 
Prof.  Owen  has  remarked  that,  as  the  marsupial  genera,  to  which 
the  ^Phascolotherium  is  most  nearly  allied,  are  now  confined  to  New 
South  Wales  and  Van  Diemen's  Land,  so  also  is  it  in  the  Australian 
seas,  that  we  find  the  Cestracion,  a  cartila- 
ginous fish  which  has  a  bony  palate,  allied  to 
those  called  Acrodus  (see  fig.  412.  p.  322.)  and 
Strophodus,  so  common  in  the  oolite  and  lias. 
IQ  the  same  Australian  seas,  also,  near  the 
shore,  we  find  the  living  Trigonia,  a  genus 
of  mollusca  so  frequently  met  with   in   the 
Stonesfield   slate.      So,  also,  the  Araucarian 
pines  are  now  abundant,  together  with  ferns, 
Portion  of  a  fossil  fruit  of  PO-  in  Australia  and  its  islands,  as  they  were  in 
fieTreatBupl:   Europe  in  the  oolitic  period.    Endogens  of  the 
°°lite'  Char"  most  Perfect  structure  are  met  with  in  oolitic 
rocks,    as,   for  example,   the    Podocarya    of 

Buckland,  a  fruit  allied  to  the   Pandanus,  found  in  the  Inferior 
Oolite  (see  fig.  383.). 

The  Stonesfield  slate,  in  its  range  from  Oxfordshire  to  the  north- 
-east, is  represented  by  flaggy  and  fissile  sandstones,  as  at  Collyweston 
in  Northamptonshire,  where,  according  to  the  researches  of  Messrs. 
Ibbetson  and  Morris*,  it  contains  many  shells,  such  as  Trigonia  angu- 
lata,  also  found  at  Stonesfield.  But  the  Northamptonshire  strata  of 
this  age  assume  a  more  marine  character,  or  appear  at  least  to  have 
been  formed  farther  from  land.  They  inclose,  however,  some  fossil 
ferns,  such  as  Pecopteris  polypodioides,  of  species  common  to  the 
oolites  of  the  Yorkshire  coast,  where  rocks  of  this  age  put  on  all 
the  aspect  of  a  true  coal-field ;  thin  seams  of  coal  having  actually 
been  worked  in  them  for  more  than  a  century. 

In  the  north-west  of  Yorkshire,  the  formation  alluded  to  consists  of 
an  upper  and  a  lower  carbonaceous  shale,  abounding  in  impressions 
of  plants,  divided  by  a  limestone  considered  by  many  geologists  as  the 
representative  of  the  Great  Oolite ;  but  the  scarcity  of  marine  fossils 
makes  all  comparisons  with  the  subdivisions  adopted  in  the  south 
extremely  difficult.  A  rich  harvest  of  fossil  ferns  has  been  obtained 
from  the  upper  carbonaceous  shales  and  sandstones  at  Gristhorpe, 
near  Scarborough  (see  figs.  384,  385.).  The  lower  shales  are  well 
exposed  in  the  sea-cliffs  at  Whitby,  and  are  chiefly  characterized 
by  ferns  and  cycadese.  They  contain,  also,  a  species  of  calamite,  and 
a  fossil  called  Equisetum  columnare,  which  maintains  an  upright 
position  in  sandstone  strata  over  a  wide  area.  Shells  of  Estheria 


*  Ibbetson    and    Moms,   Report   of  Brit.  Ass.,  1847,  p.  131.;    and  Morris, 
Geol.  Journ.,  ix.  p.  334. 


CH.  XX.] 


AND    ITS    FOSSIL 
Fig.  3S4. 


315 


Pterophyllvm  comptum.    Syn.  Cycadites  comptus. 
Upper  sandstone  aud  shale,  Gristhorpe,  near  Scarborough. 


Fig.  385. 


Fig.  386. 


Hemilelites  Brownii,  Goepp. 
Syn.  Phlebopteris  contigua,  Lind.  &  Hutt. 
Upper  carbonaceous  strata,  Lower  Oolite,  Gristhorpe,  Yorkshire. 

and  Unio,  collected  by  Mr.  Bean  from  these  Yorkshire  coal-bearing 
beds,  point  to  the  estuary  or  fluviatile  origin  of  the  deposit. 

At  Brora,  in  Sutherlandshire,  a  coal  formation,  probably  coeval 
with  the  above,  or  belonging  to  some  of  the  lower  divisions  of  the 
Oolitic  period,  has  been  mined  extensively  for  a  century  or  more. 
It  affords  the  thickest  stratum  of  pure  vegetable  matter  hitherto 
detected  in  any  secondary  rock  in  England.  One  seam  of  coal  of 
good  quality  has  been  worked  3^  feet  thick,  and  there  are  several 
feet  more  of  pyritous  coal  resting  upon  it. 

Fuller's  Earth  (h.  Tab.  p.  292.).  — Between 
the  Great  and  Inferior  Oolite,  near  Bath,  an 
argillaceous  deposit,  called  "  the  fuller's  earth," 
occurs ;  but  it  is  wanting  in  the  north  of  Eng- 
land. It  abounds  in  the  small  oyster  represented 
in  fig.  386. 

Inferior  Oolite.  —  This  formation  consists  of 
a  calcareous  freestone,  usually  of  small  thick- 
ness, which  sometimes  rests  upon,  or  is  replaced  by,  yellow  sands, 
called  the  sands  of  the  Inferior  Oolite.  These  last,  in  their  turn, 
repose  upon  the  lias  in  the  south  and  west  of  England.  Among  the 
characteristic  shells  of  the  Inferior  Oolite,  I  may  instance  Terebra- 
tulafimbria  (fig.  387.),  Rhynchonella  spinosa  (fig.  388.),  and  Phola- 
domyafidicula  (fig.  389.).  The  extinct  genus  Pleurotomaria  is  also  a 
form  very  common  in  this  division  as  well  as  in  the  Oolitic  system 


Ostrea  acuminata. 
Fuller's  Earth. 


316 


Fig.  387. 


FOSSILS   OF    THE 

Fig.  388. 


[Cn.  XX. 


Fig.  389. 


Terebratulafimbria. 
Inferior  Oolite. 


Fig.  390. 


Rhynchonella  spinosa.        a.  Pholadomyafidicula.  J  nat.  size.  Inf.  Ool 
Inferior  Oolite.  b.  Heart-shaped  anterior  termination  of  the 

same. 


Fig.  391. 


Fig.  392. 


Pleurotomaria  grunulata. 
Ferruginous  Oolite,  Normandy. 
Inferior  Oolite,  England. 


Pleurotomaria  ornata,  Sow.  Sp. 
Inferior  Oolite. 


Dysaster  ringens. 
Inf.  Ool.  Somersetshire. 


generally.  It  resembles  the  Trochus  in  form,  but  is  marked  by  a  deep 
cleft  (a,  fig.  390.  and  fig.  391.)  on  the  right  side  of  the  mouth.  The 
Dysaster  ringens  (fig.  392.)  is  an  Echinoderm  common  to  the  inferior 
Oolite  of  England  and  France,  as  are  the  three  Ammonites  of  which 
representations  are  here  given  (figs.  393,  394,  395.). 


Fig.  393. 


Ammonites  Humphresianus. 
Inferior  Oolite. 

As  illustrations  of  shells  having  a  great  vertical  range,  I  may 
allude  to  Trigonia  clavellata,  found  in  the  Upper  and  Inferior  Oolite, 
and  T.  costata,  common  to  the  Upper,  Middle,  and  Lower  Oolite ; 
also  Ostrea  Marshii  (fig.  396.),  common  to  the  Cornbrash  of  Wilts 
and  the  Inferior  Oolite  of  Yorkshire;  and  Ammonites  striatulus 
ffig.  397.)  common  to  the  Inferior  Oolite  and  Lias. 


Fig.  394. 


INFERIOR   OOLITE. 

b 


317 


Fig.  395. 


Ammonites  margaritatus,  D'Orb.    Syn.  A.  Stokesii,  Soi 
Lias. 


Fig.  396. 


Ammonites  Braikenridgii,  Sow. 

Great  Oolite,  Scarborough. 
Inf.  Ool.  Dundry ;  Calvados ;  &c. 

Fig.  397. 


Ostrea  Marshii.    %  nat.  size. 
Middle  and  Lower  Oolite. 


Ammonites  striatitlus,  Sow. 

4  nat.  size. 
Inferior  Oolite  and  Lias. 


Such  facts  by  no  means  invalidate  the  general  rule,  that  certain 
fossils  are  good  chronological  tests  of  geological  periods ;  but  they 
serve  to  caution  us  against  attaching  too  much  importance  to  single 
species,  some  of  which  may  have  a  wider,  others  a  more  confined 
vertical  range.  We  have  before  seen  that,  in  the  successive  tertiary 
formations  there  are  species  common  to  older  and  newer  groups,  yet 
these  groups  are  distinguishable  from  one  another  by  a  comparison 
of  the  whole  assemblage  of  fossil  shells  proper  to  each. 


318  MINERAL    CHARACTER    OF    THE    LIAS.          [Cn.  XXI. 


CHAPTER  XXI. 

JURASSIC  GROUP  —  continued.     LIAS. 

Mineral  character  of  Lias — Name  of  Gryphite  limestone — Fossil  shells  and  fish — 
Radiata — Ichthyodorulites — Reptiles  of  the  Lias — Ichthyosaur  and  Plesiosaur 
— Marine  Reptile  of  the  Galapagos  Islands  —  Sudden  destruction  and  burial  of 
fossil  animals  in  Lias — Fluvio-marine  beds  in  Gloucestershire,  and  insect  lime- 
stone— Fossil  plants — Origin  of  the  Oolite  and  Lias,  and  of  alternating  cal- 
careous and  argillaceous  formations  —  Oolitic  coal-field  of  Virginia,  in  the 
United  States. 

LIAS.  —  The  English  provincial  name  of  Lias  has  been  very  generally 
adopted  for  a  formation  of  argillaceous  limestone,  marl,  and  clay, 
which  forms  the  base  of  the  Oolite,  and  is  classed  by  many  geologists 
as  part  of  that  group.  They  pass,  indeed,  into  each  other  in  some 
places,  as  near  Bath,  a  sandy  marl  called  the  marlstone  of  the  Lias 
being  interposed,  and  partaking  of  the  mineral  characters  of  the 
lias  and  the  inferior  oolite.  These  last-mentioned  divisions  have 
also  some  fossils  in  common,  such  as  the  Avicula  in&quivalvis 
(fig.  398.).  Nevertheless  the  Lias  may  be  traced  throughout  a  great 

Fig.  399. 


Fig.  398. 


Avicula  incequivalvis,  Sow.  Avicula  cygnipes,  Pliil. 

Lower  Oolite.  Marlstone,  Gloucestershire;  Lias,  Yorkshire. 

part  of  Europe  as  a  separate  and  independent  group,  of  considerable 
thickness,  varying  from  500  to  1000  feet,  containing  many  peculiar 
fossils,  and  having  a  very  uniform  lithological  aspect.  Although 
usually  conformable  to  the  oolite,  it  is  sometimes,  as  in  the  Jura, 
unconformable.  In  the  environs  of  Lons-le-Saulnier,  for  instance, 
in  the  department  of  Jura,  the  strata  of  lias  are  inclined  at  an  angle 
of  about  45°,  while  the  incumbent  oolitic  marls  are  horizontal. 

The  peculiar  aspect  which  is  most  characteristic  of  the  Lias 
in  England,  France,  and  Germany  is  an  alternation  of  thin  beds  of 
blue  or  grey  limestone  having  a  surface  which  becomes  light-brown 


CH.  XXI.] 


NAME    OP    "  GRYPHITE    LIMESTONE." 


319 


when  weathered,  these  beds  being  separated  by  dark-coloured  narrow- 
argillaceous  partings,  so  that  the  quarries  of  this  rock,  at  a  distance, 
assume  a  striped  and  riband-like  appearance.* 

The  Lias  comprises, -1.  the  Upper  Lias — thin  limestone  beds  with 
clay  and  shale  ;  2.  the  Marlstone — a  coarse  shelly  limestone  ;  and  3. 
the  Lower  Lias — consisting  of  limestone,  shells,  and  clay.  These 
divisions  have  certain  fossils  in  common,  and  in  some  places  pass 
the  one  into  the  other. 

Although  the  prevailing  colour  of  the  limestone  of  this  formation 
is  blue,  yet  some  beds  of  the  lower  lias  are  of  a  yellowish  white 
colour,  and  have  been  called  white  lias.  In  some  parts  of  France, 
near  the  Vosges  mountains,  and  in  Luxembourg,  M.  E.  de  Beaumont 
has  shown  that  the  lias  containing  Gryphcea  arcuata,  Plagiostoma 
giganteum  (see  fig.  400.),  and  other  characteristic  fossils  becomes 
arenaceous ;  and  around  the  Hartz,  in  Westphalia  and  Bavaria,  the 
inferior  parts  of  the  lias  are  sandy,  and  sometimes  afford  a  building- 
stone. 

The  name  of  Gryphite  limestone  has  sometimes  been  applied  to 
the  lias,  in  consequence  of  the  great  number  of  shells  which  it  con- 

Fig.  400. 


Fig.  401. 


Gryphcea  incurvn,  Sow. 
(G.  arcuata,  Lam.) 
Lias. 


Plagiostoma  (Lima)  giganteum,  Sow. 
Inf.  Ool.  and  Lias. 

tains  of  a  species  of  oyster,  or  Gryphaa  (fig.  401.,  see  also  fig.  30. 
p.  29.).  A  large  heavy  shell  called  Hippopodium  (fig.  402.),  allied 
to  Isocardia,  is  also  characteristic  of  the  lower  lias  shales.  The 
Lias  formation  is  also  remarkable  for  being  the  oldest  of  the  second- 
ary rocks  in  which  brachiopoda  of  the  genera  Spirifer  and  Leptcena 
(figs.  403,  404.)  occur :  no  less  than  nine  species  of  Spirifer s  are 
enumerated  by  Mr.  Davidson  as  belonging  to  the  lias.  These  pallio- 
branchiate  mollusca  predominate  greatly  in  strata  older  than  the  trias ; 
but,  so  far  as  we  yet  know,  they  did  not  survive  the  liassic  epoch. 
The  marine  beds  of  the  lias  also  abound  in  cephalopoda  of  the  genera 
Belemnites,  Nautilus,  and  Ammonites  (see  figs.  405,  406,  407.). 
Among  the  Crinoids  or  Stone-lilies  of  the  Lias,  Pentacrimis 


*  Conyb.  and  Phil.,  p.  261, 


320 


FOSSILS   OF    THE    LIAS. 


[Cn.  XXI. 


Fig.  402. 


Uippopodium  ponrlerosum,  Sow. 
i  diam.    Lias,  Cheltenham 


Fig.  405. 


Nautilus  truncatus.    Lias. 


Fig.  403. 


Leptcena  Mooref,  Dav. 
Upper  Lias,  Ilminster. 


Fig.  406. 


Ammonites  Nodott'anus  ? 

A.  striatulu.1,  Sow. 

Lias. 


Ammonites  bifrons,  Brug. 
A.  Walcotii,  Sow. 

Upper  Lias  shales. 


Briareus  (fig.  408.)  is  conspicuous.  Of  Ophioderma  Egertoni  (fig. 
409.),  referable  to  the  Ophiura  of  Miiller,  perfect  specimens  have 
been  met  with  in  the  marlstone  beds  of  Dorset  and  Yorkshire. 


CH.  XXI.]  FOSSILS    OP    THE   LIAS.  321 

Fig.  408.  Fig.  4C9. 


Extracrinus  Briareus.    %  nat.  size. 
(Body,  arms,  and  part  of  stem.) 

Lias,  Lyme  Regis. 


Opkioderma  Egertont,  E.  Forbes. 
Lias  Marlstone,  Lyme  Regis. 


The  Extracrinus  Briareus  (removed  by  Major  Austin  from  Pen- 
tacrinus  on  account  of  generic  differences)  occurs  in  tangled  masses, 
forming  thin  beds  of  considerable  extent,  in  the  lias  of  Dorset, 
Gloucestershire,  and  Yorkshire.  The  remains  are  often  highly 
charged  with  pyrites.  This  Crinoid,  with  its  innumerable  tenta- 
cular arms,  appears  to  have  been  frequently  attached  to  the  drift- 
wood of  the  liassic  sea,  in  the  same  manner  as  Barnacles  float 
about  at  the  present  day.  There  is  another  species  of  Extracrinus 
and  several  of  Pentacrinus  in  the  lias  ;  and  the  latter  genus  is 
found  in  nearly  all  the  formations  from  the  lias  to  the  London 
clay  inclusive.  It  is  represented  in  the  present  seas  by  the 
delicate  and  rare  Pentacrinus  Caput-medusce  of  the  Antilles;  and 
this  indeed  is  perhaps  the  only  surviving  member  of  the  great  and 
ancient  family  of  the  Crinoids,  so  widely  represented  throughout 
the  older  formations  by  the  genera  Taxocrinus,  Actinocrinus, 
Cyathocrinus,  Encrinus,  Apiocrinus,  and  many  others. 

The  fossil  fish  re- 
semble generically 
those  of  the  oolite, 
belonging  all,  ac- 
cording to  M.  Agas- 
siz,  to  extinct  ge- 
nera, and  differ- 
ing for  the  most 
part  from  the  ich- 
thyolites  of  the 
Cretaceous  period. 


Fig.  410. 


Scales  of  Lepidotus  gigas.    Agas. 
a.  Two  of  the  scales  detached. 


322 


FOSSILS    OF    THE   LIAS. 


[Cn.  XXI. 


Among  them  is  a  species  of  Lepidotus  (L.  gigas,  Agas.),  fig.  410., 
which  is  found  in  the  lias  of  England,  France,  and  Germany.*  This 
genus  was  before  mentioned  (p.  263.)  as  occurring  in  the  Wealden, 
and  is  supposed  to  have  frequented  both  rivers  and  coasts.  Another 
genus  of  Ganoids  (or  fish  with  hard,  shining,  and  enamelled  scales), 
called  JEchmodus  (see  fig.  411.),  is  almost  exclusively  Liassic.  The 
teeth  of  a  species  of  Acrodus,  also,  are  very  abundant  in  the  lias 
(fig.  412.). 

a  Fig.  411. 


Scales  of  JEchmodus 
Leachii. 


a*  Mchmodus.    Restored  outline. 


Fig.  412. 


c.  Scales  of  Dapedius 
monilifer. 


Acrodus  nobilis,  Agas.  <tooth) ;  commonly  called  "  fossil  leech." 
Lias,  Lyme  Regis  and  Germany. 

But  the  remains  of  fish  which  have  excited  more  attention  than 
any  others  are  those  large  bony  spines  called  ichthyodorulites 
(a,  fig.  413.),  which  were  once  supposed  by  some  naturalists  to  be 

Fig.  413.  b 


Hybodus  reficulatus,  Agas.    Lias,  Lyme  Regis. 

a.  Part  of  fin,  commonly  called  Ichthyodorulite. 

b.  Tooth. 


jaws,  and  by  others,  weapons  resembling  those  of  the  living  Balistes 
and  Silurus  ;  but  which  M.  Agassiz  has  shown  to  be  neither  the  one 
nor  the  other.  The  spines,  in  the  genera  last  mentioned,  articulate 
with  the  backbone,  whereas  there  are  no  signs  of  any  such  articu- 
lation in  the  ichthyodorulites.  These  last  appear  to  have  been  bony 


Agassiz,  Pois.  Fos.  vol.  ii.  tab.  28,  29. 


CH.  XXI.]  REPTILES   OF    THE   LIAS.  323 

spines  which  formed  the  anterior  part  of  the  dorsal  fin,  like  that  of 
the  living  genera   Cestracion  and    Chimcera  (see  a,  fig.  414.).     In 

Fig.  414. 


Chimeera  monstrosa.* 
a.  Spine  forming  anterior  part  of  the  dorsal  fin. 

both  of  these  genera,  the  posterior  concave  face  is  armed  with  small 
spines,  as  in  that  of  the  fossil  Hybodus  (fig.  413.),  one  of  the  shark 
family  found  fossil  at  Lyme  Regis.  Such  spines  are  simply  im- 
bedded in  the  flesh,  and  attached  to  strong  muscles.  "  They  serve," 
says  Dr.  Buckland,  "  as  in  the  Chimczra  (fig.  414.),  to  raise  and  de- 
press the  fin,  their  action  resembling  that  of  a  moveable  mast, 
raising  and  lowering  backwards  the  sail  of  a  barge."  f 

Reptiles  of  the  Lias.  —  It  is  not,  however,  the  fossil  fish  which 
form  the  most  striking  feature  in  the  organic  remains  of  the  Lias ; 
but  the  reptiles,  which  are  extraordinary  for  their  number,  size,  and 
structure.  Among  the  most  singular  of  these  are  several  species  of 
Ichthyosaurus  and  Plesiosaurus  (figs.  415,  416.).  The  genus  Ich- 
thyosaurus, or  fish-lizard,  is  not  confined  to  this  formation,  but  has 
been  found  in  strata  as  high  as  the  lower  chalk  of  England,  and  as 
low  as  the  trias  of  Germany,  a  formation  which  immediately  succeeds 
the  lias  in  the  descending  order.|  It  is  evident  from  their  fish-like 
vertebras,  their  paddles,  resembling  those  of  a  porpoise  or  whale,  the 
length  of  their  tail,  and  other  parts  of  their  structure,  that  the  habits 
of  the  Ichthyosaurs  were  aquatic.  Their  jaws  and  teeth  show  that 
they  were  carnivorous  ;  and  the  half-digested  remains  of  fishes  and 
reptiles,  found  within  their  skeletons,  indicate  the  precise  nature 
of  their  food.§ 

A  specimen  of  the  hinder  fin  or  paddle  of  Ichthyosaurus  communis 
was  discovered  in  1840  at  Barrow-on-Soar,  by  Sir  P.  Egerton,  which 
distinctly  exhibits  on  its  posterior  margin  the  remains  of  cartila- 
ginous rays  that  bifurcate  as  they  approach  the  edge,  like  those  in 
the  fin  of  a  fish.  (See  a,  fig.  417.)  It  had  previously  been  supposed, 
says  Prof.  Owen,  that  the  locomotive  organs  of  the  Ichthyosaurus 
were  enveloped,  while  living,  in  a  smooth  integument,  like  that  of 
the  turtle  and  porpoise,  which  has  no  other  support  than  is  afforded 
by  the  bones  and  ligaments  within ;  but  it  now  appears  that  the  fin 
was  much  larger,  expanding  far  beyond  its  osseous  framework,  and 

*  Agassiz,  Poissons  Fossiles,  vol.  iii.         f  Ibid.  p.  168. 
tab.  C  fig.  1.  §  Ibid.  p.  187. 

f  Bridgewater  Treatise,  p.  290. 

T  2 


324 


SAURIANS 


[Cn.  XXI. 


deviating  widely  in  its  fish-like  rays  from  the  ordinary  reptilian  type. 
In  fig.  417.  the  posterior  bones,  or  digital  ossicles  of  the  paddle,  are 
seen  near  b ;  and  beyond  these  is  the  dark  carbonized  integument 
of  the  terminal  half  of  the  fin,  the  outline  of  which  is  beautifully 
defined.*  Prof.  Owen  believes  that,  besides  the  fore-paddles,  these 
short-  and  stiff-necked  saurians  were  furnished  with  a  tail-fin  with- 
out radiating  bones,  and  purely  tegumentary,  expanding  in  a  vertical 
direction ;  an  organ  of  motion  which  enabled  them  to  turn  their 
heads  rapidly.f 

Mr.  Conybeare  was  enabled,  in  1824,  after  examining  many  skele- 


*  Geol.  Soc.  Transact.  Second  Series, 
vol.  vi.  p.  199.  pi.  xx. 


f  Geol.   Soc.  Trans.  Second  Series, 
vol.v.  p.  511. 


CH.  XXI.]  OF   THE   LIAS.  325 

Fig.  417. 


Posterior  part  of  hind  fin  or  paddle  of  Ichthyosaurus  communis. 

tons  nearly  perfect,  to  give  an  ideal  restoration  of  the  osteology  of 
this  genus,  and  of  that  of  the  Plesiosaurus.*  (See  figs.  415,  416.) 
The  latter  animal  had  an  extremely  long  neck  and  small  head,  with 
teeth  like  those  of  the  crocodile,  and  paddles  analogous  to  those  of 
the  Ichthyosaurus,  but  larger.  It  is  supposed  to  have  lived  in 
shallow  seas  and  estuaries,  and  to  have  breathed  air  like  the  Ichthyo- 
saur  and  our  modern  cetacea.f  Some  of  the  reptiles  above  men- 
tioned were  of  formidable  dimensions.  One  specimen  of  Ichthyo- 
saurus platyodon,  from  the  lias  at  Lyme,  now  in  the  British  Mu- 
seum, must  have  belonged  to  an  animal  more  than  24  feet  in 
length ;  and  another  of  the  Plesiosaurus,  in  the  same  collection,  is 
11  feet  long.  The  form  of  the  Ichthyosaurus  may  have  fitted  it 
to  cut  through  the  waves  like  the  porpoise  ;  but  it  is  supposed  that 
the  Plesiosaurus,  at  least  the  long-necked  species  (fig.  416.),  was 
better  suited  to  fish  in  shallow  creeks  and  bays  defended  from  heavy 
breakers. 

In  many  specimens  both  of  Ichthyosaur  and  Plesiosaur  the  bones  of 
the  head,  neck,  and  tail  are  in  their  natural  position,  while  those 
of  the  rest  of  the  skeleton  are  detached  and  in  confusion.  Mr.  Stutch- 
burg  has  suggested  that  their  bodies  after  death  became  inflated  with 
gases,  and,  while  the  abdominal  viscera  were  decomposing,  the  bones, 
though  disunited,  were  retained  within  the  tough  dermal  covering 
as  in  a  bag,  until  the  whole,  becoming  water-logged,  sank  to  the 
bottom.J  As  they  belonged  to  individuals  of  all  ages  they  are  sup- 
posed, by  Dr.  Buckland,  to  have  experienced  a  violent  death ;  and 
the  same  conclusion  might  also  be  drawn  from  their  having  escaped 
the  attacks  of  their  own  predacious  race,  or  of  fishes,  found  fossil  in 
the  same  beds. 

For  the  last  twenty  years,  anatomists  have  agreed  that  these  ex- 
tinct saurians  must  have  inhabited  the  sea  ;  and  it  was  urged  that, 
as  there  are  now  chelonians,  like  the  tortoise,  living  in  fresh  water, 
and  others,  as  the  turtle,  frequenting  the  ocean,  so  there  may  have 

*  Geol.  Trans.,  Second  Series,  vol.  i.  Trans.  1st  Ser.  vol.  v.  p.  559.  ;  and 
pi-  49.  Buckland,  Bridgew.  Treat.,  p.  203. 

f  Conybeare  and  De  la  Beche.  Geol.        %  Quart.  Geol.  Journ.  vol.  ii.  p.  411. 

T  3 


326  LIAS  —  SAURIANS.  [Cn.  XXI. 

been  formerly  some  saurians  proper  to  salt,  others  to  fresh  water. 
The  common  crocodile  of  the  Ganges  is  well  known  to  frequent 
equally  that  river  and  the  brackish  and  salt  water  near  its  mouth  ; 
and  crocodiles  are  said  in  like  manner  to  be  abundant  both  in  the 
rivers  of  the  Isla  de  Pinos  (or  Isle  of  Pines),  south  of  Cuba,  and  in 
the  open  sea  round  the  coast.  More  recently  a  saurian  has  been  dis- 
covered of  aquatic  habits  and  exclusively  marine.  This  creature  was 
found  in  the  Galapagos  Islands,  during  the  visit  of  H.  M.  S.  Beagle 
to  that  archipelago,  in  1835,  and  its  habits  were  then  observed  by 
Mr.  Darwin.  The  islands  alluded  to  are  situated  under  the  equator, 
nearly  600  miles  to  the  westward  of  the  coast  of  South  America. 
They  are  volcanic ;  some  of  them  being  3000  or  4000  feet  high ; 
and  one  of  them,  Albemarle  Island,  75  miles  long.  The  climate  is 
mild ;  very  little  rain  falls ;  and,  in  the  whole  archipelago,  there 
is  only  one  rill  of  fresh  water  that  reaches  the  coast.  The  soil  is  for 
the  most  part  dry  and  harsh,  and  the  vegetation  scanty.  The  birds, 
reptiles,  plants,  and  insects  are,  with  very  few  exceptions,  of  species 
found  no  where  else  in  the  world,  although  all  partake,  in  their 
general  form,  of  a  South  American  type.  Of  the  mammalia,  says 
Mr.  Darwin,  one  species  alone  appears  to  be  indigenous,  namely,  a 
large  and  peculiar  kind  of  mouse ;  but  the  number  of  lizards,  tor- 
toises, and  snakes  is  so  great,  that  it  may  be  called  a  land  of  reptiles. 
The  variety,  indeed,  of  species  is  small ;  but  the  individuals  of  each 
are  in  wonderful  abundance.  There  is  a  turtle,  a  large  tortoise 
(  Testudo  Indicus),  four  lizards,  and  about  the  same  number  of  snakes, 
but  no  frogs  or  toads.  Two  of  the  lizards  belong  to  the  family 
Iguanidcz  of  Bell,  and  to  a  peculiar  genus  (Amblyrhynchus)  esta- 
blished by  that  naturalist,  and  so  named  from  their  obtusely  trun- 
cated head  and  short  snout.*  Of  these  lizards  one  is  terrestrial  in 
its  habits,  and  burrows  in  the  ground,  swarming  everywhere  on  the 
land,  having  a  round  tail,  and  a  mouth  somewhat  resembling  in  form 
that  of  the  tortoise.  The  other  is  aquatic,  and  has  its  tail  flattened 
laterally  for  swimming  (see  fig.  418.)  "This  marine  saurian,"  says 
Mr.  Darwin,  "  is  extremely  common  on  all  the  islands  throughout 

Fig.  418. 


Amblyrhynchus  cristatus,  Bell.    Length  varying  from  3  to  4  feet.    The  only  existing  marine  lizard 

now  known. 

a.  Tooth,  natural  size  and  magnified. 
*  Au§Avs,  amblys,  blunt ;  and  £v7xos»  rhynchus,  snout. 


CH.  XXI.]  SUDDEN   DESTRUCTION   OF    SAUEIANS.  327 

the  archipelago.  It  lives  exclusively  on  the  rocky  sea-beaches,  and 
I  never  saw  one  even  ten  yards  inshore.  The  usual  length  is  about 
a  yard,  but  there  are  some  even  4  feet  long.  It  is  of  a  dirty  black 
colour,  sluggish  in  its  movements  on  the  land ;  but,  when  in  the 
water,  it  swims  with  perfect  ease  and  quickness  by  a  serpentine 
movement  of  its  body  and  flattened  tail,  the  legs  during  this  time 
being  motionless,  and  closely  collapsed  on  its  sides.  Their  limbs  and 
strong  claws  are  admirably  adapted  for  crawling  over  the  rugged  and 
fissured  masses  of  lava  which  everywhere  form  the  coast.  In  such 
situations,  a  group  of  six  or  seven  of  these  hideous  reptiles  may 
oftentimes  be  seen  on  the  black  rocks,  a  few  feet  above  the  surf, 
basking  in  the  sun  with  outstretched  legs.  Their  stomachs,  on  being 
opened,  were  found  to  be  largely  distended  with  minced  sea-weed,  of 
a  kind  which  grows  at  the  bottom  of  the  sea  at  some  little  distance 
from  the  coast.  To  obtain  this,  the  lizards  go  out  to  sea  in  shoals. 
One  of  these  animals  was  sunk  in  salt  water,  from  the  ship,  with 
a  heavy  weight  attached  to  it,  and  on  being  drawn  up  again  after 
an  hour  it  was  quite  active  and  unharmed.  It  is  not  yet  known  by 
the  inhabitants  where  this  animal  lays  its  eggs ;  a  singular  fact, 
considering  its  abundance,  and  that  the  natives  are  well  acquainted 
with  the  eggs  of  the  terrestrial  Amblyrhynchus,  which  is  also  herbi- 
vorous." * 

In  those  deposits  now  forming  by  the  sediment  washed  away  from 
the  wasting  shores  of  the  Galapagos  Islands  the  remains  of  saurians, 
both  of  the  land  and  sea,  as  well  as  of  chelonians  and  fish,  may  be 
mingled  with  marine  shells,  without  any  bones  of  land  quadrupeds  or 
batrachian  reptiles  ;  yet  even  here  we  should  expect  the  remains  of 
marine  mammalia  to  be  imbedded  in  the  new  j>trata,  for  there  are 
seals,  besides  several  kinds  of  cetacea,  on  the  Galapagian  shores ;  and, 
in  this  respect,  the  parallel  between  the  modern  fauna,  above  described, 
and  the  ancient  one  of  the  lias  would  not  hold  good. 

Sudden  destruction  of  saurians.  —  It  has  been  remarked,  and 
truly,  that  many  of  the  fish  and  saurians,  found  fossil  in  the  lias, 
must  have  met  with  sudden  death  and  immediate  burial ;  and  that  the 
destructive  operation,  whatever  may  have  been  its  nature,  was  often 
repeated. 

"  Sometimes,"  says  Dr.  Buckland,  "  scarcely  a  single  bone  or  scale 
has  been  removed  from  the  place  it  occupied  during  life ;  which  could 
not  have  happened  had  the  uncovered  bodies  of  these  saurians  been 
left,  even  for  a  few  hours,  exposed  to  putrefaction,  and  to  the  attacks 
of  fishes,  and  other  smaller  animals  at  the  bottom  of  the  sea."f  Not 
only  are  the  skeletons  of  the  Ichthyosaurs  entire,  but  sometimes  the 
contents  of  their  stomachs  still  remain  between  their  ribs,  as  before 
remarked,  so  that  we  can  discover  the  particular  species  of  fish  on 
which  they  lived,  and  the  form  of  their  excrements.  Not  unfre- 
quently  there  are  layers  of  these  coprolites,  at  different  depths  in  the 
lias,  at  a  distance  from  any  entire  skeletons  of  the  marine  lizards 

*  Darwin's  Journal,  chap.  xix.  t  Bridgew.  Treat.,  p.  125. 

Y  4 


328  FOSSILS    OF    THE   LIAS.  tCfl.  XXI. 

from  which  they  were  derived;  "as  if,"  says  Sir  H.  de  la  Beche, 
"  the  muddy  bottom  of  the  sea  received  small  sudden  accessions  of 
matter  from  time  to  time,  covering  up  the  coprolites  and  other  ex- 
uviae which  had  accumulated  during  the  intervals."  *  It  is  farther 
stated  that,  at  Lyme  Regis,  those  surfaces  only  of  the  coprolites 
which  lay  uppermost  at  the  bottom  of  the  sea  have  suffered  partial 
decay,  from  the  action  of  water  before  they  were  covered  and  pro- 
tected by  the  muddy  sediment  that  has  afterwards  permanently 
enveloped  them,  f 

Numerous  specimens  of  the  Calamary  or  pen-and-ink  fish  ( Geo- 
teuthis  Bollensis,  Schuble  sp.)  have  also  been  met  with  in  the  lias 
at  Lyme,  with  the  ink-bags  still  distended,  containing  the  ink  in 
a  dried  state,  chiefly  composed  of  carbon,  and  but  slightly  impreg- 
nated with  carbonate  of  lime.  These  cephalopoda,  therefore,  must, 
like  the  saurians,  have  been  soon  buried  in  sediment;  for,  if  long 
exposed  after  death,  the  membrane  containing  the  ink  would  have 
decayed,  f 

As  we  know  that  river-fish  are  sometimes  stifled,  even  in  their 
own  element,  by  muddy  water  during  floods,  it  cannot  be  doubted 
that  the  periodical  discharge  of  large  bodies  of  turbid  fresh  water  into 
the  sea  may  be  still  more  fatal  to  marine  tribes.  In  the  "  Principles 
of  Geology"  I  have  shown  that  large  quantities  of  mud  and  drowned 
animals  have  been  swept  down  into  the  sea  by  rivers  during  earth- 
quakes, as  in  Java,  in  1699 ;  and  that  undescribable  multitudes  of 
dead  fishes  have  been  seen  floating  on  the  sea  after  a  discharge  of 
noxious  vapours  during  similar  convulsions.  §  But,  in  the  intervals 
between  such  catastrophes,  strata  may  have  accumulated  slowly  in 
the  sea  of  the  lias,  some  being  formed  chiefly  of  one  description  of 
shell,  such  as  ammonites,  others  of  gryphites. 

From  the  above  remarks  the  reader  will  infer  that  the  lias  is  for 
the  most  part  a  marine  deposit.  Some  members,  however,  of  the 
series,  especially  in  the  lowest  part  of  it,  have  an  estuary  character, 
and  must  have  been  formed  within  the  influence  of  rivers.  In  Glou- 
cestershire, where  there  is  a  good  type  of  the  lias  of  the  West  of 
England,  it  has  been  divided  into  an  upper  mass  of  shale  with  a  base 
of  marlstone,  and  a  lower  series  of  shales  with  underlying  limestones 
and  shales.  We  learn  from  the  researches  of  the  Rev.  P.  B.  Brodie  ||, 
that  in  the  superior  of  these  two  divisions  numerous  remains  of  in- 
sects and  plants  have  been  detected  in  several  places,  mingled  with 
marine  shells;  but  in  the  inferior  division  similar  fossils  are  still 
more  plentiful.  One  band,  rarely  exceeding  a  foot  in  thickness,  has 
been  named  the  "  insect  limestone."  It  passes  upwards  into  a  shale 
containing  Cypris  and  Estheria,  and  is  charged  with  the  wing-cases 
of  several  genera  of  coleoptera,  and  with  some  nearly  entire  beetles,  of 
which  the  eyes  are  preserved.  The  nervures  of  the  wings  of  neurop- 

*  Geological  Researches,  p.  334.  §  See   Principles,  Index,  Lancerote, 

f  Buckland,  Bridgew.  Treat.,  p.  307.     Graham  Island,  Calabria. 
|  Ibid.  ||  A  History  of  Fossil  Insects,  &c. 

1846.     London. 


CH.  XXI.]  FOSSIL   PLANTS  —  LIAS.  329 

terous  insects  (fig.  419.)  are  beautifully 
perfect  in  this  bed.  Ferns,  with  leaves 
of  monocotyledonous  plants,  and  some 
apparently  brackish   and   freshwater 
shells,  accompany  the  insects  in  several 
places,  while  in  others  marine  shells 
Winogwe°rf  lirs?raeucesStersSh&.frTRehv!   predominate,  the  fossils  varying  appa- 
p.  B.  Brodie.)  rently  as  we  examine  the  bed  nearer  or 

farther  from  the  ancient  land,  or  the  source  whence  the  fresh  water  was 
derived.  There  are  two,  or  even  three,  bands  of  "  insect  limestone  "  in 
several  sections,  and  they  have  been  ascertained  by  Mr.  Brodie  to  retain 
the  same  lithological  and  zoological  characters  when  traced  from  the 
centre  of  Warwickshire  to  the  borders  of  the  southern  part  of  Wales. 
After  studying  300  specimens  of  these  insects  from  the  lias,  Mr.  West- 
wood  declares  that  they  comprise  both  wood-eating  and  herb-de- 
vouring beetles  of  the  Linnean  genera  Elater,  Carabus,  &c.,  besides 
grasshoppers  (  Gryllus),  and  detached  wings  of  dragon-flies  and  may- 
flies, or  insects  referable  to  the  Linnean  genera  Libellula,  Ephemera, 
Hemerobius,  and  Panorpa,  in  all  belonging  to  no  less  than  twenty- 
four  families.  The  size  of  the  species  is  usually  small,  and  such  as 
taken  alone  would  imply  a  temperate  climate ;  but  many  of  the  asso- 
ciated organic  remains  of  other  classes  must  lead  to  a  different 
conclusion. 

Fossil  plants. — Among  the  vegetable  remains  of  the  Lias,  several 
species  of  Zamia  have  been  found  at  Lyme 
Regis,  and  the  remains  of  coniferous  plants 
at  Whitby.    'Fragments  of  wood  are  com- 
mon, and  often  converted  into  limestone. 
That  some  of  this  wood,  though  now  petri- 
fied, was  soft  when  it  first  lay  at  the  bot- 
tom of  the  sea,  is  shown  by  a  specimen  now 
in  the  museum  of  the  Geological  Society  (see  fig.  420.),  which  has  the 
form  of  an  ammonite  indented  on  its  surface. 

M.  Ad.  Brongniart  enumerates  forty-seven  liassic  acrogens,  most 
of  them  ferns  ;  and  fifty  gymnogens,  of  which  thirty -nine  are  cycads, 
and  eleven  conifers.  Among  the  cycads  the  predominance  of  Zamites 
and  Nilssonia,  and  among  the  ferns  the  numerous  genera  with  leaves 
having  reticulated  veins  (as  in  fig.  385.  p.  315.),  are  mentioned  as 
botanical  characteristics  of  this  era.*  The  absence  as  yet  from  the 
Lias  and  Ooolite  of  all  signs  of  dicotyledonous  angiosperms  is  worthy 
of  notice.  The  leaves  of  such  plants  are  frequent  in  tertiary  strata, 
and  occur  in  the  Cretaceous,  though  less  plentifully  (see  above, 
p.  267.)  The  angiosperms  seem,  therefore,  to  have  been  at  the  least 
comparatively  rare  in  these  older  secondary  periods,  when  more 
space  was  occupied  by  the  Cycads  and  Conifers. 

Origin  of  the  Oolite  and  Lias. — If  we  now  endeavour  to  restore, 
in  imagination,  the  ancient  condition  of  the  European  area  at  the 

*  Tableau  des  Veg.  Fos.  1849,  p.  105. 


330  ORIGIN    OF    THE    OOLITE    AND   LIAS.  [Cn.  XXI. 

period  of  the  Oolite  and  Lias,  we  must  conceive  a  sea  in  which  the 
growth  of  coral-reefs  and  shelly  limestones,  after  proceeding  without 
interruption  for  ages,  was  liable  to  be  stopped  suddenly  by  the  depo- 
sition of  clayey  sediment.  Then,  again,  the  argillaceous  matter,  de- 
void of  corals,  was  deposited  for  ages,  and  attained  a  thickness  of 
hundreds  of  feet,  until  another  period  arrived  when  the  same  space 
was  again  occupied  by  calcareous  sand,  or  solid  rocks  of  shell  and 
coral,  to  be  again  succeeded  by  the  recurrence  of  another  period  of 
argillaceous  deposition.  Mr.  Conybeare  has  remarked  of  the  entire 
group  of  Oolite  and  Lias,  that  it  consists  of  repeated  alternations  of 
clay,  sandstone,  and  limestone,  following  each  other  in  the  same 
order.  Thus  the  clays  of  the  lias  are  followed  by  the  sands  of  the 
inferior  oolite,  and  these  again  by  shelly  and  coralline  limestone 
(Bath  oolite,  &c.)  ;  so,  in  the  middle  oolite,  the  Oxford  clay  is  fol- 
lowed by  calcareous  grit  and  coral  rag ;  lastly,  in  the  upper  oolite, 
the  Kimmeridge  clay  is  followed  by  the  Portland  sand  and  limestone.* 
The  clay  beds,  however,  as  Sir  H.  De  la  Beche  remarks,  can  be  fol- 
lowed over  larger  areas  than  the  sands  or  sandstones,  f  It  should 
also  be  remembered  that  while  the  oolitic  system  becomes  arenaceous 
and  resembles  a  coal-field  in  Yorkshire,  it  assumes  in  the  Alps  an 
almost  purely  calcareous  form,  the  sands  and  clays  being  omitted ; 
and  even  in  the  intervening  tracts  it  is  more  complicated  and  variable 
than  appears  in  ordinary  descriptions.  Nevertheless,  some  of  the 
clays  and  intervening  limestones  do  retain,  in  reality,  a  pretty  uni- 
form character  for  distances  of  from  400  to  600  miles  from  east  to 
west  and  north  to  south. 

According  to  M.  Thirria,  the  entire  oolitic  group  in  the  depart- 
ment of  the  Haute  Saone,  in  France,  may  be  equal  in  thickness  to 
that  of  England ;  but  the  importance  of  the  argillaceous  divisions  is 
in  the  inverse  ratio  to  that  which  they  exhibit  in  England,  where 
they  are  about  equal  to  twice  the  thickness  of  the  limestones,  whereas, 
in  the  part  of  France  alluded  to,  they  reach  only  about  a  third  of  that 
thickness.^  In  the  Jura  the  clays  are  still  thinner ;  and  in  the  Alps 
they  thin  out  and  almost  vanish. 

In  order  to  account  for  such  a  succession  of  events,  we  may  ima- 
gine, first,  the  bed  of  the  ocean  to  be  the  receptacle  for  ages  of  fine 
argillaceous  sediment,  brought  by  oceanic  currents,  which  may  have 
communicated  with  rivers,  or  with  part  of  the  sea  near  a  wasting 
coast.  This  mud  ceases,  at  length,  to  be  conveyed  to  the  same  region, 
either  because  the  land  which  had  previously  suffered  denudation 
is  depressed  and  submerged,  or  because  the  current  is  deflected  in 
another  direction  by  the  altered  shape  of  the  bed  of  the  ocean  and 
neighbouring  dry  land.  By  such  changes  the  water  becomes  once 
more  clear  and  fit  for  the  growth  of  stony  zoophytes.  Calcareous 
sand  is  then  formed  from  comminuted  shell  and  coral,  or,  in  some 
cases,  arenaceous  matter  replaces  the  clay ;  because  it  commonly 


*  Con.  and  Phil.,  p.  166.  f  Burat's  D  Aubuisson,  torn.  ii.  p.  456. 

f  Geol.  Researches,  p.  337. 


CH.  XXL]        OOLITE   AND  LIAS  OP  THE  UNITED  STATES.         331 

happens  that  the  finer  sediment,  being  first  drifted  farthest  from 
coasts,  is  subsequently  overspread  by  coarse  sand,  after  the  sea  has 
grown  shallower,  or  when  the  land,  increasing  in  extent,  whether  by 
upheaval  or  by  sediment  filling  up  parts  of  the  sea,  has  approached 
nearer  to  the  spots  first  occupied  by  fine  mud. 

In  order  to  account  for  another  great  formation,  like  the  Oxford 
clay,  again  covering  one  of  coral  limestone,  we  must  suppose  a  sink- 
ing down  like  that  which  is  now  taking  place  in  some  existing 
regions  of  coral  between  Australia  and  South  America.  The  oc- 
currence of  subsidences,  on  so  vast  a  scale,  may  have  caused  the 
bed  of  the  ocean  and  the  adjoining  land,  throughout  great  parts  of 
the  European  area,  to  assume  a  shape  favourable  to  the  deposition  of 
another  set  of  clayey  strata ;  and  this  change  may  have  been  suc- 
ceeded by  a  series  of  events  analogous  to  that  already  explained,  and 
these  again  by  a  third  series  in  similar  order.  Both  the  ascending 
and  descending  movements  may  have  been  extremely  slow,  like  those 
now  going  on  in  the  Pacific ;  and  the  growth  of  every  stratum  of 
coral,  a  few  feet  of  thickness,  may  have  required  centuries  for  its 
completion,  during  which  certain  species  of  organic  beings  disap- 
peared from  the  earth,  and  others  were  introduced  in  their  place ;  so 
that,  in  each  set  of  strata,  from  the  Lias  to  the  Upper  Oolite,  some 
peculiar  and  characteristic  fossils  were  embedded. 

Oolite  and  Lias  of  the  United  States. 

There  are  large  tracts  on  the  globe,  as  in  Russia  and  the  United 
States,  where  all  the  members  of  the  oolitic  series  are  unrepresented. 
In  the  state  of  Virginia,  however,  at  the  distance  of  about  13  miles 
eastward  of  Richmond,  the  capital  of  that  State,  there  is  a  regular 
coal-field  occurring  in  a  depression  of  the  granite  rocks  (see  section, 
fig.  421.),  which  Professor  W.  B.  Rogers  first  correctly  referred  to 

Fig.  421. 

1  '.  1 

Ii  li  II 

sfes. 


Section  showing  the  geological  position  of  the  James  River,  or  East  Virginian  Coal-field. 
A.  Granite,  gneiss,  &c.  B.  Coal-measures. 

C.  Tertiary  strata.  D.  Drift  or  ancient  alluvium. 

the  age  of  the  lower  part  of  the  Jurassic  group.  This  opinion  I 
was  enabled  to  confirm  after  collecting  a  large  number  of  fossil 
plants,  fish,  and  shells,  and  examining  the  coal-field  throughout  its 
whole  area.  It  extends  26  miles  from  north  to  south,  and  from  4 
to  12,  from  east  to  west.  The  plants  consist  chiefly  of  zamites,  cala- 
mites,  and  equisetums,  and  these  last  are  very  commonly  met  with  in 


332  OOLITE  AND  LIAS  [Cn.  XXI. 

a  vertical  position  more  or  less  compressed  perpendicularly.  It  is 
clear  that  they  grew  in  the  places  where  they  are  now  buried  in  strata 
of  hardened  sand  and  mud.  I  found  them  maintaining  their  erect 
attitude,  at  points  many  miles  distant  from  others,  in  beds  both  above 
and  between  the  seams  of  coal.  In  order  to  explain  this  fact  we  must 
suppose  such  shales  and  sandstones  to  have  been  gradually  accumu- 
lated during  the  slow  and  repeated  subsidence  of  the  whole  region. 

It  is  worthy  of  remark  that  the  Equisetum  columnare  of  these 
Virginian  rocks  appears  to  be  undistinguishable  from  the  species 
found  in  the  oolitic  sandstones  near  Whitby  in  Yorkshire,  where  it 
also  is  met  with  in  an  upright  position.  One  of  the  Yirginian  fossil 
ferns,  Pecopteris  Whitbyensis,  is  also  a  species  common  to  the  York- 
shire oolites.*  These  Virginian  coal-measures  are  composed  of  grits, 
sandstones,  and  shales,  exactly  resembling  those  of  older  or  primary 
date  in  America  and  Europe,  and  they  rival  or  even  surpass  the 
latter  in  the  richness  and  thickness  of  the  coal-seams.  One  of  these, 
the  main  seam,  is  in  some  places  from  30  to  40  feet  thick,  composed 
of  pure  bituminous  coal.  On  descending  a  shaft  800  feet  deep,  in 
the  Blackheath  mines  in  Chesterfield  county,  I  found  myself  in  a 
chamber  more  than  40  feet  high,  caused  by  the  removal  of  this  coal. 
Timber  props  of  great  strength  supported  the  roof,  but  they  were 
seen  to  bend  under  the  incumbent  weight.  The  coal  is  like  the 
finest  kinds  shipped  at  Newcastle,  and  when  analysed  yields  the  same 
proportions  of  carbon  and  hydrogen,  a  fact  worthy  of  notice  when 
we  consider  that  this  fuel  has  been  derived  from  an  assemblage  of 
plants  very  distinct  specifically, .  and  in  part  generically,  from  those 
which  have  contributed  to  the  formation  of  the  ancient  or  paleozoic 
coal. 

The  fossil  fish  of  these  Richmond  strata  belong  to  the  liassic  genus 
Tetragonolepis  (dEchmodus),  see  fig.  411.,  and  to  a  new  genus  which 
I  have  called  Dictyopyge.  Shells  are  very  rare,  as  usually  in  all 

Fig.  422.' 


a.  Posidonomya  or  Est heria .?  t  6.  Young  of  same. 

Oolitic  coal-shale,  Richmond,  Virginia. 

*  See  description  of  the  coal-field  by  f  Possibly,   as    suggested    by  Prof, 

the  author,  and  of  the  plants  by  C.  J.  F.  Morris  (Geol.  Journ.  vol.  iii.  p.  275.), 

Bunbury,  Esq.,  Quart.  Geol.  Journ,,  vol.  these  delicate  bivalves  may  prove  to  be- 

iii.  p.  281.  long  to  the  crustacean  genus  Estheria. 


CH.  XXI.]         OF    THE  UNITED   STATES    AND   INDIA.  333 

coal-bearing  deposits,  but  a  species  of  Posidonomya  is  in  such  pro- 
fusion in  some  shaly  beds  as  to  divide  them  like  the  plates  of  mica 
in  micaceous  shales  (see  fig.  422.). 

In  India,  especially  in  Cutch,  a  formation  occurs  clearly  referable 
to  the  oolitic  and  liassic  type,  as  shown  by  the  shells,  corals,  and 
plants ;  and  there  also  coal  has  been  procured  from  one  member  of 
the  group. 


334 


NEW   RED    SANDSTONE. 


[Cn.  XXII. 


CHAPTER  XXII. 


TRIAS  OR  NEW  RED  SANDSTONE  GROUP. 

Distinction  between  New  and  Old  Red  Sandstone — Between  Upper  and  Lower 
New  Red  —  The  Trias  and  its  three  divisions  —  Most  largely  developed  in  Ger- 
many— Keuper  and  its  fossils  —  Muschelkalk  and  fossils — Fossil  plants  of  the 
Banter  —  Triassic  group  in  England — Bone-bed  of  Axmouth  and  Aust  —  Red 
Sandstone  of  Warwickshire  and  Cheshire  — Footsteps  of  Cheirotherium  in  England 
and  Germany — Osteology  of  the  Labyrinthodon  —  Identification  of  this  Ba- 
trachian  with  the  Cheirotherium — Triassic  mammifer —  Origin  of  Red  Sandstone 
and  Rock-salt  —  Hypothesis  of  saline  volcanic  exhalations — Theory  of  the  pre- 
cipitation of  salt  from  inland  lakes  or  lagoons — Saltness  of  the  Red  Sea — New 
Red  Sandstone  in  the  United  States — Fossil  footprints  of  birds  and  reptiles  in 
the  valley  of  the  Connecticut — Antiquity  of  the  Red  Sandstone  containing  them. 

BETWEEN  the  Lias  and  the  Coal  (or  Carboniferous  group)  there  is 
interposed,  in  the  midland  and  western  counties  of  England,  a  great 
series  of  red  loams,  shales,  and  sandstones,  to  which  the  name  of  the 
"New  Red  Sandstone  formation"  was  first  given,  to  distinguish  it 
from  other  shales  and  sandstones  called  the  "  Old  Red"  (c.  fig.  423.), 
often  identical  in  mineral  character,  which  lie  immediately  beneath 
the  coal  (b). 

Fig.  423. 


a.  New  red  sandstone. 


b.  Coal. 


c.  Old  red. 


The  name  of  "  Red  Marl"  has  been  incorrectly  applied  to  the  red 
clays  of  this  formation,  as  before  explained  (p.  13.),  for  they  are 
remarkably  free  from  calcareous  matter.  The  absence,  indeed,  of 
carbonate  of  lime,  as  well  as  the  scarcity  of  organic  remains,  together 
with  the  bright  red  colour  of  most  of  the  rocks  of  this  group,  causes 
a  strong  contrast  between  it  and  the  Jurassic  formations  before  de- 
scribed. 

Before  the  distinctness  of  the  fossil  remains  characterizing  the 
upper  and  lower  part  of  the  English  New  Red  had  been  clearly 
recQgnized,  it  was  found  convenient  to  have  a  common  name  for 
all  the  strata  intermediate  in  position  between  the  Lias  and  Coal ; 
and  the  term  "Poikilitic"  was  proposed  by  Messrs.  Cony beare  and 
Buckland*,  from  Trot/ctXoc,  poikilos,  variegated,  some  of  the  most 
characteristic  strata  of  this  group  having  been  called  variegated  by 

*  Buckland,  Bridg.  Treat.,  vol.  ii.  p.  38. 


CH.  XXII.]      KEUPER    AND    MUSCHELKALK   FORMATIONS.        335 

Werner,  from  their  exhibiting  spots  and  streaks  of  light-blue,  green, 
and  buff  colour,  in  a  red  base. 

A  single  term,  thus  comprehending  both  Upper  and  Lower  New 
Red,  or  the  Triassic  and  Permian  groups  of  modern  classifications, 
may  still  be  useful  in  describing  districts  where  we  have  to  speak  of 
masses  of  red  sandstone  and  shale,  referable,  in  part,  to  both  these 
eras,  but  which,  in  the  absence  of  fossils,  it  is  impossible  to  divide. 


TRIAS  OR  UPPER  NEW  RED  SANDSTONE  GROUP. 

The  accompanying  table  will  explain  the  subdivisions  generally 
adopted  for  the  uppermost  of  the  two  systems  above  alluded  to,  and 
the  names  given  to  them  in  England  and  on  the  Continent. 


Synonyms. 


German.  French. 

fa.  Saliferous    and    gyp-~l 

seous     shales     and  >  Keuper      ,.,.  t.»    Marnes  irisees. 
Trias  or  Upper  |  sandstone       -         -  J 


I  shall  first  describe  this  group  as  it  occurs  in  South-western  and 
North-western  Germany,  for  it  is  far  more  fully  developed  there 
than  in  England  or  France.  It  has  been  called  the  Trias  by  German 
writers,  or  the  Triple  Group,  because  it  is  separable  into  three  distinct 
formations,  called  the  "  Keuper,"  the  "  Muschelkalk,"  and  the  "Bun- 
ter-sandstein." 

The  Keuper,  the  first  or  newest  of  these,  is  1000  feet  thick  in 
Wiirtemberg,  and  is  divided  by  Alberti  into  salidstone,  gypsum,  and 
carbonaceous  slate-clay.*     Remains  of  Reptiles,  called  Nothosaurus 
Fitr  424  and  Phytosaurus,  have  been  found  in  it  with 

Labyrinthodon  ;  the  detached  teeth,  also,  of 
placoid  fish  and  of  rays,  and  of  the  genera 
Saurichthys  and  Gyrolepis  (figs.  433,  434., 
p.  338.).  The  plants  of  the  Keuper  are 
generically  very  analogous  to  those  of  the 
lias  and  oolite,  consisting  of  ferns,  equise- 
taceous  plants,  cycads,  and  conifers,  with 

Equisetites  columnaris.   (Syn.  Equi-    a    few    doubtful    monocotyledons.       A   few 
setum  columnare.)     Fragment  of  .  ,  -.-,       •      .-.  7 

stem,  and  a  srnal!  portion  of  same    SpCClOS,     SUCll     as     J^qUlSetlteS     COlUmnariS, 

are  common  to  this  group  and  the  oolite. 

The  Muschelkalk  consists  chiefly  of  a  compact,  greyish  limestone, 
but  includes  beds  of  dolomite  in  many  places,  together  with  gypsum 
and  rock-salt.  This  limestone,  a  rock  wholly  unrepresented  in  Eng- 
land, abounds  in  fossil  shells,  as  the  name  implies.  Among  the  ce- 
phalopoda there  are  no  belemnties,  and  no  ammonites  with  foliated 
sutures,  as  in  the  incumbent  lias  and  oolite,  but  a  genus  allied  to  the 
Ammonite,  called  Ceratites  by  De  Haan,  in  which  the  descending 

*  Monog.  des  Bunten  Sandsteins. 


336 


MUSCHELKALK   AND   FOSSILS. 

a  Fig.  425.  b 


[Cn.  XXII. 


Ceratites  nodosus.    Muschelkalk. 

a.  Side  view.  b.  Front  view. 

c.  Partially  denticulated  outline  of  the  septa  dividing  the  chambers. 

lobes  (see  «,  b,  c,  fig.  425.)  terminate  in  a  few  small  denticulations 
pointing  inwards.  Among  the  bivalve  shells,  the  Posidonia  minuta, 
Goldf.  (Posidonomya  minuta,  Bronn),  see  fig.  426.,  is  abundant,  ranging 
through  the  Keuper,  Muschelkalk,  and  Bunter-sandstein ;  and  Avi- 
cula  socialis,  fig.  427.,  having  a  similar  range,  is  very  characteristic 
of  the  Muschelkalk  in  Germany,  France,  and  Poland. 


Fig.  426. 


Fig.  427. 


Posidonia  minuta,  a.  Avicula  socialis  ft.  Side  view  of  same. 

Goldf.   (Posido-  Characteristic  of  the  Muschelkalk. 

nomya   minuta, 
Bronn.) 

The  abundance  of  the  heads  and  stems  of  lily  encrinites,  Encrinus 
Fig.  428.  liliiformis,  fig.  428.  (or  Encrinites  moniliformis), 

show  the  slow  manner  in  which  some  beds  of  this 
limestone  have  been  formed  in  clear  sea-water. 
The  star-fish  called  Aspidura  loricata,  fig.  429., 

Fig.  420. 


Encrinus  liliiformis,  Schlott.    Syn.  E.  moniltformis. 
Body,  arms,  and  part  of  stem. 
a.  Section  of  stem. 
Muschelkalk. 


Aspidura  loricata,  Agas. 
a.  Upper  side. 
b-  Lower  side. 
Muschelkalk. 


CH.  XXII.]  THE   BUNTER-SANDSTEIN.  337 

is  as  yet  peculiar  to  the  Muschelkalk.  In  the  same  formation  are 
found  ganoid  fish  with  heterocercal  tails,  of  the  genus  Placodus.  (See 
fig.  430.) 


Fig.  430. 


Fig.  431. 


Palatal  teeth  of  Placodus  gigas. 
Muschelkalk. 


a.  Voltzia  heterophylla.    (Syn.  Voltzia 

brevifolia.) 

b.  portion  of  same  magnified  to  show 

fructification.    Sulzbad. 
Bunter-sandstein. 


The  Bunter-sandstein  consists  of  various  coloured  sandstones, 
dolomites,  and  red-clays,  with  some  beds,  especially  in  the  Hartz,  of 
calcareous  pisolite  or  roe-stone,  the  whole  sometimes  attaining  a 
thickness  of  more  than  1000  feet.  The  sandstone  of  the  Vosges, 
according  to  Von  Meyer,  is  proved,  by  the  presence  of  Labyrin- 
thodon,  to  belong  to  this  lowest  member  of  the  Triassic  group.  At 
Sulzbad  (or  Soultz-les-bains),  near  Strasburg,  on  the  flanks  of  the 
Vosges,  many  plants  have  been  obtained  from  the  "  bunter,"  espe- 
cially conifers  of  the  extinct  genus  Voltzia,  peculiar  to  this  period, 
in  which  even  the  fructification  has  been  preserved.  (See  fig.  431.) 

Out  of  thirty  species  of  ferns,  cycads,  conifers,  and  other  plants, 
enumerated  by  M.  Ad.  Brongniart,  in  1849,  as  coming  from  the 
"  gres  bigarre,"  or  Bunter,  not  one  is  common  to  the  Keuper.*  This 
difference,  however,  may  arise  partly  from  the  fact  that  the  flora  of 
"  the  Bunter  "  has  been  almost  entirely  derived  from  one  district  (the 
neighbourhood  of  Strasburg),  and  its  peculiarities  may  be  local. 

The  footprints  of  a  reptile  (Labyrinihodori)  have  been  observed  on 
the  clays  of  this  member  of  the  Trias,  near  Hildburghausen,  in  Sax- 
ony, impressed  on  the  upper  surface  of  the  beds,  and  standing  out  as 
casts  in  relief  from  the  under  sides  of  incumbent  slabs  of  sandstone. 
To  these  I  shall  again  allude  in  the  sequel ;  they  attest,  as  well  as 
the  accompanying  ripple-marks,  and  the  cracks  which  traverse  the 
clays,  the  gradual  deposition  of  the  beds  of  this  formation  in  shallow 
water,  and  sometimes  between  high  and  low  water. 

Triassic  Group  in  England. 

In  England  the  Lias  is  succeeded  by  conformable  strata  of  red  and 
green  marl,  or  clay.  There  intervenes,  however,  both  in  the  neigh- 
bourhood of  Axmouth,  in  Devonshire,  and  in  the  cliffs  of  Westbury 


*  Tableau  des  Genres  de  Veg.  Fos.,  Diet.  Univ.  1849. 
z 


338  TRIASSIC   GROUP   IN   ENGLAND.  [Cn.  XXII. 

and  Aust,  in  Gloucestershire,  on  the  banks  of  the  Severn,  a  dark- 
coloured  stratum,  well  known  by  the  name  of  the  "  bone-bed."  It 
abounds  in  the  remains  of  saurians  and  fish,  and  was  formerly  classed 
as  the  lowest  bed  of  the  Lias ;  but  Sir  P.  Egerton  has  shown  that  it 
should  be  referred  to  the  Upper  New  Red  Sandstone,  for  it  contains 
an  assemblage  of  fossil  fish  which  are  either  peculiar  to  this  stratum 
or  belong  to  species  well  known  in  the  Muschelkalk  of  Germany. 
These  fish  belong  to  the  genera  Acrodus,  Hybodus,  Gyrolepis,  and 
Saurichthys. 

Among  those  common  to  the  English  bone-bed  and  the  Muschel- 
kalk of  Germany  are  Hybodus  plicatilis  (fig.  432.),  Saurichthys  api- 
calis  (fig.  433.),  Gyrolepis  tenuistriatus  (fig.  434.),  and  G.  Albertii. 
Remains  of  saurians  have  also  been  found  in  the  bone-bed,  and  plates 
of  an  Encrinus. 

Fig.  433.  Fig.  434. 

* 

Tig.  432. 


Hybodus  plicatilis.    Teeth.    Bone-bed, 
Aust  and  Axmouth. 

Saurichthys  apicalis.  Gyrolepis  tenuistriatus. 

Tooth;    nat.  size, and  Scale;    nat.  size,    and 

magnified.     Axmouth.  magnified.    Axmouth. 

The  strata  of  red  and  green  marl,  which  follow  the  bone -bed  in 
the  descending  order  at  Axmouth  and  Aust,  are  destitute  of  organic 
remains ;  as  is  the  case,  for  the  most  part,  in  the  corresponding  beds 
in  almost  every  part  of  England.  But  fossils  have  been  found  at  a 
few  localities  in  sandstones  of  this  formation,  in  Worcestershire  and 
Warwickshire,  and  among  them  the  bivalve  shell  called  Posidonia 
minuta,  Goldf.,  before  mentioned  (fig.  426.  p.  336.). 

The  upper  member  of  the  English  "New  Red"  containing  this 
shell,  in  those  parts  of  England,  is,  according  to  Messrs.  Murchison 
and  Strickland,  600  feet  thick,  and  consists  chiefly  of  red  marl  or 
slate,  with  a  band  of  sandstone.  Ichthyodorulites,  or  spines  of 
Hybodus,  teeth  of  fishes,  and  footprints  of  reptiles  were  observed  by 
the  same  geologists  in  these  strata  * ;  and  the  remains  of  a  saurian, 
called  Rhynchosaurus,  have  been  found  in  this  portion  of  the  Trias 
at  Grinsell,  near  Shrewsbury. 

In  Cheshire  and  Lancashire  the  gypseous  and  saliferous  red  shales 
and  clays  of  the  Trias  are  between  1000  and  1500  feet  thick.  In 
some  places  lenticular  masses  of  rock-salt  are  interpolated  between 
the  argillaceous  beds,  the  origin  of  which  will  be  spoken  of  in  the 
sequel. 

The  lower  division  or  English  representative  of  the  "  Bunter " 

*  Geol.  Trans.,  Sec,  Ser.,  vol.  v.  p.  318.  &c. 


CH.  XXII.]      FOSSIL  FOOTSTEPS  IN  NEW  KED  SANDSTONE.      339 

attains  a  thickness  of  600  feet  in  the  counties  last  mentioned.  Be- 
sides red  and  green  shales  and  red  sandstones,  it  comprises  much 
soft  white  quartzose  sandstone,  in  which  the  trunks  of  silicified  trees 
have  been  met  with  at  Allesley  Hill,  near  Coventry.  Several  of 
them  were  a  foot  and  a  half  in  diameter,  and  some  yards  in  length, 
decidedly  of  coniferous  wood,  and  showing  rings  of  annual  growth.* 
Impressions,  also,  of  the  footsteps  of  animals  have  been  detected  in 
Lancashire  and  Cheshire  in  this  formation.  Some  of  the  most  re- 
markable occur  a  few  miles  from  Liverpool,  in  the  whitish  quartzose 
sandstone  of  Storton  Hill,  on  the  west  side  of  the  Mersey.  They 
bear  a  close  resemblance  to  tracks  first  observed  in  a  member  of  the 
Upper  New  Red  Sandstone,  at  the  village  of  Hesseberg,  near  Hild- 
burghausen,  in  Saxony,  to  which  I  have  already  alluded.  For  many 
years  these  footprints  have  been  referred  to 
Fig.  435.  a  iarge  unknown  quadruped,  provisionally 

named  Cheirotherium  by  Professor  Kaup, 
because  the  marks  both  of  the  fore  and  hind 
feet  resembled  impressions  made  by  a  human 
hand.  (See  fig.  435.)  The  footmarks  at 
Hesseberg  are  partly  concave,  and  partly  in 
relief;  the  former,  or  the  depressions,  are 
seen  upon  the  upper  surface  of  the  sandstone 
slabs,  but  those  in  relief  are  only  upon  the 
lower  surfaces,  being  in  fact  natural  casts, 
formed  in  the  subjacent  footprints  as  in 
moulds.  The  larger  impressions,  which  seem 
to  be  those  of  the  hind  foot,  are  generally 
8  inches  in  length,  and  5  in  width,  and  one  was  12  inches  long. 
Near  each  large  footstep,  and  at  a  regular  distance  (about  an  inch 

Fig.  43a 


Single  footstep  of  Cheirothe- 
rium. Bunter  Sandstein, 
Saxony ;  one  eighth  of  nat. 
size. 


Line  of  footsteps  on  slab  of  sandstone.    Hildburghausen,  in  Saxony.     g| 

and  a  half),  before  it,  a  smaller  print  of  a  fore  foot,  4  inches  long  and 
3  inches  wide,  occurs.  The  footsteps  follow  each  other  in  pairs,  each 
pair  in  the  same  line,  at  intervals  of  14  inches  from  pair  to  pair. 
The  large  as  well  as  the  small  steps  show  the  great  toes  alternately 
on  the  right  and  left  side ;  each  step  makes  the  print  of  five  toes,  the 
first  or  great  toe  being  bent  inwards  like  a  thumb.  Though  the  fore 
and  hind  foot  differ  so  much  in  size,  they  are  nearly  similar  in  form. 
The  similar  footmarks  afterwards  observed  in  a  rock  of  corre- 
sponding age  at  Storton  Hill  were  imprinted  on  five  thin  beds  of 
clay,  superimposed  one  upon  the  other  in  the  same  quarry,  and  sepa- 
rated by  beds  of  sandstone.  On  the  lower  surface  of  the  sandstone 


*  Buckland,  Proc.  Geol.  Soc.  vol.  ii.  p.  439.;  and  Murchison  and  Strickland, 
Geol.  Trans.,  Second  Ser.,  vol.  v.  p.  347. 

z  2 


340  FOSSIL   REMAINS  [Cn.  XXII. 

strata,  the  solid  casts  of  each  impression  are  salient,  in  high  relief, 
and  afford  models  of  the  feet,  toes,  and  claws  of  the  animals  which 
trod  on  the  clay.  On  the  same  surfaces  Mr.  J.  Cunningham  dis- 
covered (1839)  distinct  casts  of  rain-drop  markings. 

As  neither  in  Germany  nor  in  England  any  bones  or  teeth  had 
been  met  with  in  the  same  identical  strata  as  the  footsteps,  anato- 
mists indulged,  for  several  years,  in  various  conjectures  respecting 
the  mysterious  animals  from  which  they  might  have  been  derived. 
Professor  Kaup  suggested  that  the  unknown  quadruped  might  have 
been  allied  to  the  Marsupialia  ;  for  in  the  kangaroo  the  first  toe  of 
the  fore  foot  is  in  a  similar  manner  set  obliquely  to  the  others,  like  a 
thumb,  and  the  disproportion  between  the  fore  and  hind  feet  is  also 
very  great.  But  M.  Link  conceived  that  some  of  the  four  species  of 
animals  of  which  the  tracks  had  been  found  in  Saxony  might  have 
been  gigantic  Batraehians ;  and  Dr.  Buckland  designated  some  of 
the  footsteps  as  those  of  a  small  web-footed  animal,  probably  croco- 
dilian. 

In  the  course  of  these  discussions  several  naturalists  of  Liverpool, 
in  their  report  on  the  Storton  quarries,  declared  their  opinion  that 
each  of  the  thin  seams  of  clay  in  which  the  sandstone  casts  were 
moulded  had  formed  successively  a  surface  above  water,  over  which 
the  Cheirotherium  and  other  animals  walked,  leaving  impressions  of 
their  footsteps,  and  that  each  layer  had  been  afterwards  submerged 
by  a  sinking  down  of  the  surface,  so  that  a  new  beach  was  formed  at 
low  water  above  the  former,  on  which  other  tracks  were  then  made. 
The  repeated  occurrence  of  ripple-marks  at  various  heights  and 
depths  in  the  red  sandstone  of  Cheshire  had  been  explained  in  the 
same  manner.  It  was  also  remarked  that  impressions  of  such  depth 
and  clearness  could  only  have  been  made  by  animals  walking  on  the 
land,  as  their  weight  would  have  been  insufficient  to  make  them  sink 
so  deeply  in  yielding  clay  under  water.  They  must  therefore  have 
been  air-breathers. 

When  the  inquiry  had  been  brought  to  this  point,  the  reptilian 
remains  discovered  in  the  Trias,  both  of  Germany  and  England,  were 
earefull|-  examined  by  Prof.  Owen.     He  found,  after  a  microscopic 
investigation  of  the  teeth  from  the  German  sandstone  called  Keuper, 
and  from  the  sandstone  of  Warwick  and  Leamington  (fig.  437.), 
that  neither  of  them  could  be  referred  to  true  saurians,  although  they 
had  been  named  Mastodonsaurus  and  Phytosaurus 
by  Jager.     It  appeared  that  they  were  of  the  Ba- 
trachian  order,  and  attested  the  former  existence 
of  frogs  of  gigantic  dimensions  in  comparison  with 
any  now  living.    Both  the  Continental  and  English 
fossil  teeth  exhibited  a  most  complicated  texture, 
differing  from  that  previously  observed  in  any  rep- 
Tooth  of  Labyrintho-  tile,  whether  recent  or  extinct,  but  most  nearly  ana- 

don;  nat.  size.    War-  .  _  J  „ 

wick  sandstone.          logons  to  the  Ichthyosaurus.     A  section  ot  one  ot 
these  teeth  exhibits  a  series  of  irregular  folds,  re- 
sembling the  labyrinthic  windings  of  the  surface  of  the  brain  ;  and 


CH.  XXII.]  OF   LABYR1NTHODON.  341 

from  this  character  Prof,  Owen  has  proposed  the  name  Labyrintho- 
don  for  the  new  genus.  The  annexed'  representation  (fig.  438.)  of 
part  of  one  is  given  from  his  "  Odontography,"  plate  64  A.  The 
entire  length  of  this  tooth  is  supposed  to  have  been  about  three 
inches  and  a  half,  and  the  breadth  at  the  base  one  inch  and  a  half. 

Fig.  438. 


Transverse  section  of  tooth  of  Labyrinthodon  Jaegeri,  Owen  (Mastodonsaurus  Jaegeri, 

Meyer) ;  nat.  size,  and  a  segment  magnified. 
a.  Pulp  cavity,  from  which  the  processes  of  pulp  and  dentine  radiate. 

When  Prof.  Owen  had  satisfied  himself,  from  an  inspection  of  the 
cranium,  jaws,  and  teeth,  that  a  gigantic  Batracfyian  had  existed  at 
the  period  of  the  Trias  or  Upper  New  Red  Sandstone,  he  soon  found, 
from  the  examination  of  various  bones  derived  from  the  same  forma- 
tion, that  he  could  define  three  species  of  Labyrinthodon,  and  that  in 
this  genus  the  hind  extremities  were  much  larger  than  the  anterior 
ones.  This  circumstance,  coupled  with  the  fact  of  the  Labyrinthodon 
having  existed  at  the  period  when  the  Cheirotherian  footsteps  were 
made,  was  the  first  step  towards  the  identification  of  those  tracks 
with  the  newly  discovered  Batrachian.  It  was  at  the  same  time 
observed  that  the  footmarks  of  Cheirotherium  were  more  like  those 
of  toads  than  of  any  other  living  animal ;  and,  lastly,  that  the  size  of 
the  three  species  of  Labyrinthodon  corresponded  with  the  size  of 
three  different  kinds  of  footprints  which  had  already  been  supposed 
to  belong  to  three  distinct  Cheirotheria.  It  was  moreover  inferred, 
with  confidence,  that  the  Labyrinthodon  was  an  air-breathing  reptile 
from  the  structure  of  the  nasal  cavity,  in  which  the  posterior  outlets 
were  at  the  back  part  of  the  mouth,  instead  of  being  directly  under 
the  anterior  or  external  nostrils.  It  must  have  respired  air  after 
the  manner  of  saurians,  and  may  therefore  have  imprinted  on  the 
shore  those  footsteps,  which,  as  we  have  seen,  could  not  have  origi- 
nated from  an  animal  walking  under  water. 

It  is  true  that  the  structure  of  the  foot  is  still  wanting,  and  that  a 

Z  3 


342  FOSSIL   REMAINS   OF   LABYRINTHODON.       [Cn.  XXII. 

more  connected  and  complete  skeleton  is  required  for  demonstration  ; 
but  the  circumstantial  evidence  above  stated  is  strong  enough  to  pro- 
duce the  conviction  that  the  Cheirotherium  and  Labyrinthodon  are 
one  and  the  same. 

In  order  to  show  the  manner  in  which  one  of  these  formidable 
Batrachians  may  have  impressed  the  mark  of  its  feet  upon  the 
shore,  Prof.  Owen  has  attempted  a  restoration,  of  which  a  reduced 
copy  is  annexed. 

Fig.  439. 


Restored  outline  of  Labyrinthodon  pacliygnathus,  Owen. 

The  only  bones  of  this  species  at  present  known  are  those  of  the 
head,  the  pelvis,  and  part  of  the  scapula,  which  are  shown  by  stronger 
lines  in  the  above  figure.  There  is  reason  for  believing  that  the 
head  was  not  smooth  externally,  but  protected  by  bony  scutella. 
This  character  and  the  presence  of  strong  conical  teeth  implanted  in 
sockets,  together  with  the  elongated  form  of  the  head,  induce  many 
able  anatomists,  such  as  Von  Meyer  and  Mantell,  to  regard  the  Laby- 
rinthodons  as  more  allied  to  crocodiles  than  to  frogs.  But  the  double 
occipital  condyles,  the  position  of  some  of  the  teeth  on  the  vomer  and 
palatine  bones,  and  other  characters,  are  considered  by  Messrs. 
Jager  and  Owen  to  give  them  superior  claims  to  be  classed  as  ba- 
trachians.  That  they  occupy  an  intermediate  place  is  clear,  but  too 
little  is  yet  known  of  the  entire  skeleton  to  enable  us  to  determine 
the  exact  amount  of  their  affinity  to  one  or  other  of  the  above-named 
great  divisions  of  reptiles. 

Triassic  Mammifer  (Microlestes  antiquus,  Plieninger). — In  the 
year  1847,  Professor  Plieninger,  of  Stuttgart,  published  a  descrip- 
tion of  two  fossil  molar  teeth,  referred  by  him  to  a  warm-blooded 
quadruped*,  which  he  obtained  from  a  bone-breccia  in  Wiirtemberg 
occurring  between  the  lias  and  the  keuper.  As  the  announcement  of 
so  novel  a  fact  has  never  met  with  the  attention  it  deserved,  we  are 
indebted  to  Dr.  Jager,  of  Stuttgart,  for  having  recently  reminded  us 
of  it  in  his  Memoir  on  the  Fossil  Mammalia  of  Wiirtemberg.  f 

Fig.  440.  represents  the  tooth  first  found,  taken  from  the  plate  pub- 
lished in  1847,  by  Professor  Plieninger ;  and  fig.  441.  is  a  drawing  of 
the  same  executed  from  the  original  by  Mr.  Hermann  von  Meyer, 

*  Wurtembergisch.  Naturwissen  Jah-  Nat.  Cur.  1850,  p.  902.  For  figures,  see 
reshefte,  3  Jahr.  Stuttgart,  1847.  ibid,  plate  xxi.  figs.  14,  15,  16,  17. 

f  Nov.  Act.  Acad.  Caesar.  Leopold. 


CH.  XXII.]  FOSSIL       AMMIFER   IN   TRIAS.  343 

which  he  has  been  kind  enough  to  send  me.     Fig.  442.  is  a  second 
and  larger  molar,  copied  from  Dr.  Jager's  plate  Ixxi.,  fig.  15. 


Fig.  440. 


Fig.  441. 


Fig.  442. 


Microlestes  antiquus,  Plieninger.    Molar  tooth  magni-  Microlestes  antiquus, 

fied.     Upper  Trias,  Diegerloch,  near  Stuttgart,  Wiir-  Plien. 

temberg.  View  of  same  molar 

a.  View  of  inner  side  ?  b.  Same,  outer  side  ?  as  No.  440.  From  a 

c.  Same  in  profile.  d.  Crown  of  same.  drawing    by    Her- 

man von  Meyer. 

a.  View  of  inner 

side? 

b.  Crown  of  same. 

Professor  Plieninger  inferred  in  1847,  from  the 
double  fangs  of  this  tooth  and  their  unequal  size,  and 
from  the  form  and  number  of  the  protuberances  or 
cusps  on  the  flat  crowns,  that  it  was  the  molar  of  a 
Mammifer ;  and  considering  it  as  predaceous,  probably 
insectivorous,  he  calls  it  Microlestes,  from  jut/cpoc, 
little,  and  Anornc,  a  beast  of  prey.  Soon  afterwards, 

Molar  of  Microles-    ,        „          ,    ,,  -i    ,       ,1          1^,1  i         -,.      ' 

tesf  Plien.  4  times   he  lound  the  second  tooth,  also  at  the  same  locality, 
44oargeFrome  the   Diegerloch,  about  two  miles  to  the  south-east  of  Stutt- 
loch,  stfutt?arf.er"  gart.     Some  of  its  cusps  are  broken,  but  there  seem  to 
have  been  six  of  them  originally.     From  its  agree- 
ment in  general  characters,  it  is  supposed  by  Professor  Plieninger  to 
be  referable  to  the  same  animal,  but  as  it  is  fouriimes  as  big,  it  may 
perhaps  have  belonged  to  another  allied  species.      This  molar  is 
attached  to  the  matrix  consisting  of  sandstone,  whereas  the  tooth, 
fig.  440.,  is  isolated.     Several  fragments  of  bone,  differing  in  struc- 
ture from  that  of  the  associated  saurians  and  fish,  and  believed  to  be 
mammalian,  were  imbedded  near  them  in  the  same  rock. 

Mr.  Waterhouse,  of  the  British  Museum,  after  studying  the  annexed 
figs.  440,  441,  442.,  and  the  descriptions  of  Prof.  Plieninger,  observes, 
that  not  only  the  double  roots  of  the  teeth,  and  their  crowns  present- 
ing several  cusps,  resemble  those  of  Mammalia,  but  the  cingulum 
also,  or  ridge  surrounding  the  base  of  that  part  of  the  body  of  the 
tooth  which  was  exposed  or  above  the  gum,  is  a  character  distin- 
guishing them  from  fish  and  reptiles.  "The  arrangement  of  the 
six  cusps  or  tubercles  in  two  rows,  in  fig.  440.,  with  a  groove  or  de- 
pression between  them,  and  the  oblong  form  of  the  tooth,  lead  him, 
he  says,  to  regard  it  as  a  molar  of  the  lower  jaw.  Both  the  teeth 
differ  from  those  of  the  Stonesfield  Mammalia,  but  do  not  supply 
sufficient  data  for  determining  to  what  order  they  belonged. 

Professor  Plieninger  has  sent  me  a  cast  of  the  smaller  tooth,  which 
exhibits  well  the  characteristic  mammalian  test,  the  double  fang ;  but 
Prof.  Owen,  to  whom  I  have  shown  it,  is  not  able  to  recognise  its 
affinity  with  any  mammalian  type,  recent  or  extinct,  known  to  him. 

4 


344  ORIGIN   Or    RED    SANDSTONE  [Cn.  XXII. 

It  has  already  been  stated  that  the  stratum  in  which  the  above- 
mentioned  fossils  occur  is  intermediate  between  the  lias  and  the 
uppermost  member  of  the  trias.  That  it  is  really  triassic  may  be 
deduced  from  the  following  considerations.  In  Wiirtemberg  there 
are  two  "bone-beds,"  one  of  great  extent,  and  very  rich  in  the 
remains  of  fish  and  reptiles,  which  intervenes  between  the  muschel- 
kalk  and  keuper,  the  other,  containing  the  Microlestes,  less  extensive 
.and  fossiliferous,  which  rests  on  the  keuper,  or  superior  member  of 
the  trias,  and  is  covered  by  the  sandstone  of  the  lias.  The  last- 
mentioned  breccia,  therefore,  occupies  nearly  the  same  place  as  the 
well-known  English  "  bone-bed "  of  Axmouth  and  Aust-cliff  near 
Bristol,  which  is  shown  above,  p.  338.,  to  include  characteristic 
species  of  muschelkalk  fish,  of  the  genus  Saurichthys,  Hybodus,  and 
Gyrolepis.  In  both  the  Wiirtemberg  bone-beds  these  three  genera  are 
also  found,  and  one  of  the  species,  Saurichthys  Mougeotii,  is  common 
to  both  the  lower  and  upper  breccias,  as  is  also  a  remarkable  reptile 
called  Nothosaurus  mirabilis.  The  saurian  called  Belodon  by  H. 
Von  Meyer,  of  the  Thecodont  family,  is  another  Triassic  form,  asso- 
ciated at  Diegerloch  with  Microlestes. 

Previous  to  this  discovery  of  Professor  Plieninger,  the  most  ancient 
of  known  fossil  Mammalia  were  those  of  the  Stonesfield  slate,  above 
described,  p.  312.,  no  representative  of  this  class  having  as  yet  been 
met  with  in  the  Fuller's  earth,  or  inferior  Oolite,  nor  in  any  member 
of  the  Lias. 

Origin  of  Red  Sandstone  and  Rock  Salt. 

We  have  seen  that,  in  various  parts  of  the  world,  red  and  mottled 
clays  and  sandstones,  of  several  distinct  geological  epochs,  are  found 
associated  with  salt,  gypsum,  magnesian  limestone,  or  with  one  or  all 
of  these  substances.  There  is,  therefore,  in  all  likelihood,  a  general 
cause  for  such  a  coincidence.  Nevertheless,  we  must  not  forget  that 
there  are  dense  masses  of  red  and  variegated  sandstones  and  clays, 
thousands  of  feet  in  thickness,  and  of  vast  horizontal  extent,  wholly 
devoid  of  saliferous  or  gypseous  matter.  There  are  also  deposits  of 
gypsum  and  of  muriate  of  soda,  as  in  the  blue  clay  formation  of 
Sicily,  without  any  accompanying  red  sandstone  or  red  clay. 

To  account  for  deposits  of  red  mud  and  red  sand,  we  have  simply 
to  suppose  the  disintegration  of  ordinary  crystalline  or  metamorphic 
schists.  Thus,  in  the  eastern  Grampians  of  Scotland,  in  the  north 
of  Forfarshire,  for  example,  the  mountains  of  gneiss,  mica-schist,  and 
clay-slate  are  overspread  with  alluvium,  derived  from  the  disinte- 
gration of  those  rocks ;  and  the  mass  of  detritus  is  stained  by  oxide 
of  iron,  of  precisely  the  same  colour  as  the  Old  Red  Sandstone  of  the 
adjoining  Lowlands.  Now  this  alluvium  merely  requires  to  be  swept 
down  to  the  sea,  or  into  a  lake,  to  form  strata  of  red  sandstone  and 
red  marl,  precisely  like  the  mass  of  the  "  Old  Red  "  or  "  New  Red  " 
systems  of  England,  or  those  tertiary  deposits  of  Auvergne  (see 
p.  199.),  before  described,  which  are  in  lithological  characters  quite 


CH.  XXII.]  AND  KOCK  SALT.  345 

undistinguishable.  The  pebbles  of  gneiss  in  the  Eocene  red  sand- 
stone of  Auvergne  point  clearly  to  the  rocks  from  which  it  has  been 
derived.  The  red  colouring  matter  may,  as  in  the  Grampians,  have 
been  furnished  by  the  decomposition  of  hornblende  or  mica,  which 
contain  oxide  of  iron  in  large  quantity. 

It  is  a  general  fact,  and  one  not  yet  accounted  for,  that  scarcely 
any  fossil  remains  are  preserved  in  stratified  rocks  in  which  this 
oxide  of  iron  abounds  ;  and  when  we  find  fossils  in  the  New  or  Old 
Red  Sandstone  in  England,  it  is  in  the  gray,  and  usually  calcareous 
beds,  that  they  occur. 

The  gypsum  ?.nd  saline  matter,  occasionally  interstratified  with 
such  red  clays  and  sandstones  of  various  ages,  primary,  secondary, 
and  tertiary,  have  been  thought  by  some  geologists  to  .be  of  volcanic 
origin.  Submarine  and  subaerial  exhalations  often  occur  in  regions 
of  earthquakes  and  volcanos  far  from  points  of  actual  eruption,  and 
charged  with  sulphur,  sulphuric  salts,  and  with  common  salt  or 
muriate  of  soda.  In  a  word,  such  "  solfataras  "  are  vents  by  which 
all  the  products  which  issue  in  a  state  of  sublimation  from  the  craters 
of  active  volcanos  obtain  a  passage  from  the  interior  of  the  earth  to 
the  surface.  That  such  gaseous  emanations  and  mineral  springs, 
impregnated  with  the  ingredients  before  enumerated,  and  often  in- 
tensely heated,  .continue  to  flow  out  unaltered  in  composition  and 
temperature  for  ages,  is  well  known.  But  before  we  can  decide  on 
their  real  instrumentality  in  producing  in  the  course  of  ages  beds  of 
gypsum,  salt,  and  dolomite,  we  require  to  know  more  respecting  the 
chemical  changes  actually  in  progress  in  seas  where  volcanic  agency 
is  at  work. 

The  origin  of  rock-salt,  however,  is  a  problem^of  so  much  interest 
in  theoretical  geology  as  to  demand  the  discussion  of  another  hypo- 
thesis advanced  on  the  subject ;  namely,  that  which  attributes  the 
precipitation  of  the  salt  to  evaporation,  whether  of  inland  lakes  or  of 
lagoons  communicating  with  the  ocean. 

At  Northwich,  in  Cheshire,  two  beds  of  salt,  in  great  part  unmixed 
with  earthy  matter,  attain  the  extraordinary  thickness  of  90  and 
even  100  feet.  The  upper  surface  of  the  highest  bed  is  very  uneven, 
forming  cones  and  irregular  figures.  Between  the  two  masses  there 
intervenes  a  bed  of  indurated  clay,  traversed  with  veins  of  salt. 
The  highest  bed  thins  off  towards  the  south-west,  losing  15  feet  in 
thickness  in  the  course  of  a  mile.*  The  horizontal  extent  of  these 
particular  masses  in  Cheshire  and  Lancashire  is  not  exactly  known  ; 
but  the  area,  containing  saliferous  clays  and  sandstones,  is  supposed 
to  exceed  150  miles  in  diameter,  while  the  total  thickness  of  the 
trias  in  the  same  region  is  estimated  by  Mr.  Ormerod  at  more  than 
1700  feet.  Ripple-marked  sandstones,  and  the  footprints  of  animals, 
before  described,  are  observed  at  so  many  levels  that  we  may  safely 
assume  the  whole  area  to  have  undergone  a  slow  and  gradual  de- 
pression during  the  formation  of  the  Red  Sandstone.  The  evidence 

*  Ormerod,  Quart.  Geol.  Joura.  1848,  vol.  iv.  p.  277. 


346  RUNN   OF   CUTCH.  [Cn.  XXII. 

of  such  a  movement,  wholly  independent  of  the  presence  of  salt 
itself  is  very  important  in  reference  to  the  theory  under  consider- 
ation. 

In  the  "  Principles  of  Geology  "  (chap.  27.),  I  published  a  map, 
furnished  to  me  by  the  late  Sir  Alexander  Burnes,  of  that  singular 
flat  region  called  the  Runn  of  Cutch,  near  the  delta  of  the  Indus, 
which  is  7000  square  miles  in  area,  or  equal  in  extent  to  about  one- 
fourth  of  Ireland.  It  is  neither  land  nor  sea,  but  is  dry  during  a 
part  of  every  year,  and  again  covered  by  salt  water  during  the 
monsoons.  Some  parts  of  it  are  liable,  after  long  intervals,  to  be 
overflowed  by  river-water.  Its  surface  supports  no  grass,  but  is 
encrusted  over,  here  and  there,  by  a  layer  of  salt,  about  an  inch 
in  depth,  caused  by  the  evaporation  of  sea-water.  Certain  tracts 
have  been  converted  into  dry  land  by  upheaval  during  earthquakes 
since  the  commencement  of  the  present  century,  and,  in  other  di- 
rections, the  boundaries  of  the  Runn  have  been  enlarged  by  sub- 
sidence. That  successive  layers  of  salt  might  be  thrown  down,  one 
upon  the  other,  over  thousands  of  square  miles,  in  such  a  region,  is 
undeniable.  The  supply  of  brine  from  the  ocean  would  be  as  in- 
exhaustible as  the  supply  of  heat  from  the  sun  to  cause  evaporation. 
The  only  assumption  required  to  enable  us  to  explain  a  great  thick- 
ness of  salt  in  such  an  area  is,  the  continuance,  for  an  indefinite 
period,  of  a  subsiding  movement,  the  country  preserving  all  the  time 
a  general  approach  to  horizontality.  Pure  salt  could  only  be  formed 
in  the  central  parts  of  basins,  where  no  sand  could  be  drifted  by  the 
wind,  or  sediment  be  brought  by  currents.  Should  the  sinking  of 
the  ground  be  accelerated,  so  as  to  let  in  the  sea  freely,  and  deepen 
the  water,  a  temporary  suspension  of  the  precipitation  of  salt  would 
be  the  only  result.  On  the  other  hand,  if  the  area  should  dry  up, 
ripple-marked  sands  and  the  footprints  of  animals  might  be  formed, 
where  salt  had  previously  accumulated.  According  to  this  view  the 
thickness  of  the  salt,  as  well  as  of  the  accompanying  beds  of  mud 
and  sand,  becomes  a  mere  question  of  time,  or  requires  simply  a 
repetition  of  similar  operations. 

Mr.  Hugh  Miller,  in  an  able  discussion  of  this  question,  refers  to 
Dr.  Frederick  Parrot's  account,  in  his  journey  to  Ararat  (1836),  of 
the  salt  lakes  of  Asia.  In  several  of  these  lakes  west  of  the  river 
Manech,  "  the  water,  during  the  hottest  season  of  the  year,  is  covered 
on  its  surface  with  a  crust  of  salt  nearly  an  inch  thick,  which  is  col- 
lected with  shovels  into  boats.  The  crystallization  of  the  salt  is 
effected  by  rapid  evaporation  from  the  sun's  heat  and  the  supersatura- 
tion  of  the  water  with  muriate  of  soda ;  the  lake  being  so  shallow  that 
the  little  boats  trail  on  the  bottom  and  leave  a  furrow  behind  them,  so 
that  the  lake  must  be  regarded  as  a  wide  pan  of  enormous  super- 
ficial extent,  in  which  the  brine  can  easily  reach  the  degree  of  con- 
centration required." 

Another  traveller,  Major  Harris,  in  his  "  Highlands  of  Ethiopia," 
describes  a  salt  lake,  called  the  Bahr  Assal,  near  the  Abyssinian 
frontier,  which  once  formed  the  prolongation  of  the  Gulf  of  Tadjara, 


CH.XXII.]  SALTNESS    OF    THE   RED    SEA.  347 

but  was  afterwards  cut  off  from  the  gulf  by  a  broad  bar  of  lava  or  of 
land  upraised  by  an  earthquake.  "  Fed  by  no  rivers,  and  exposed  in 
a  burning  climate  to  the  unmitigated  rays  of  the  sun,  it  has  shrunk 
into  an  elliptical  basin,  seven  miles  in  its  transverse  axis,  half  filled 
with  smooth  water  of  the  deepest  crerulian  hue,  and  half  with  a  solid 
sheet  of  glittering  snow-white  salt,  the  offspring  of  evaporation." 
"  If,"  says  Mr.  Hugh  Miller,  "  we  suppose,  instead  of  a  barrier  of 
lava,  that  sand-bars  were  raised  by  the  surf  on  a  flat  arenaceous  coast 
during  a  slow  and  equable  sinking  of  the  surface,  the  waters  of  the 
outer  gulf  might  occasionally  topple  over  the  bar,  and  supply  fresh 
brine  when  the  first  stock  had  been  exhausted  by  evaporation."  * 

We  may  add  that  the  permanent  impregnation  of  the  waters  of  a 
large  shallow  basin  with  salt,  beyond  the  proportion  which  is  usual 
in  the  ocean,  would  cause  it  to  be  uninhabitable  by  molluscs  or  fish,  as 
is  the  case  in  the  Dead  Sea,  and  the  muriate  of  soda  might  remain  in 
excess,  even  though  it  were  occasionally  replenished  by  irruptions  of 
the  sea.  Should  the  saline  deposit  be  eventually  submerged,  it  might, 
as  we  have  seen  from  the  example  of  the  Runn  of  Cutch,  be  covered 
by  a  freshwater  formation  containing  fluviatile  organic  remains ;  and 
in  this  way  the  apparent  anomaly  of  beds  of  sea-salt  and  clays  devoid 
of  marine  fossils,  alternating  with  others  of  freshwater  origin,  may  be 
explained. 

Dr.  G.  Buist,  in  a  recent  communication  to  the  Bombay  Geographical 
Society  (vol.  ix.),  has  asked  how  it  happens  that  the  Red  Sea  should  not 
exceed  the  open  ocean  in  saltness,  by  more  than  T^  th  per  cent.  The 
Red  Sea  receives  no  supply  of  water  from  any  quarter  save  through 
the  Straits  of  Babelmandeb  ;  and  there  is  not  a  single  river  or  rivulet 
flowing  into  it  from  a  circuit  of  4000  miles  of  shore.  The  countries 
around  are  all  excessively  sterile  and  arid,  and  composed,  for  the 
most  part,  of  burning  deserts.  From  the  ascertained  evaporation  in 
the  sea  itself,  Dr.  Buist  computes  that  nearly  8  feet  of  pure  water 
must  be  carried  off  from  the  whole  of  its  surface  annually,  this  being 
probably  equivalent  to  x^th  part  of  its  whole  volume.  The  Red  Sea, 
therefore,  ought  to  have  1  per  cent,  added  annually  to  its  saline  con- 
tents ;  and  as  these  constitute  4  per  cent,  by  weight,  or  2^  per  cent, 
in  volume  of  its  entire  mass,  it  ought,  assuming  the  average  depth  to 
be  800  feet,  which  is  supposed  to  be  far  beyond  the  truth,  to  have 
been  converted  into  one  solid  salt  formation  in  less  than  3000  years.f 
Does  the  Red  Sea  receive  a  supply  of  water  from  the  ocean,  through 
the  narrow  Straits  of  Babelmandeb,  sufficient  to  balance  the  loss  by 
evaporation  ?  And  is  there  an  undercurrent  of  heavier  saline  water 
annually  flowing  outwards  ?  If  not,  in  what  manner  is  the  excess  of 
salt  disposed  of?  An  investigation  of  this  subject  by  our  nautical 
surveyors  may  perhaps  aid  the  geologist  in  framing  a  true  theory  of 
the  origin  of  rock-salt. 

*  Hugh  Miller,  First  Impressions  of  f  Buist,  Trans,  of  Bombay  Geograph. 
England,  1847,  pp.  183.  214.  Soc.  1850,  vol.  ix,  p.  38. 


348         NEW   RED   SANDSTONE    OP   THE   U.  STATES.       [Cn.  XXII. 

On  the  New  Red  Sandstone  of  the  Valley  of  the  Connecticut  River  in 
the  United  States. 

In  a  depression  of  the  granitic  or  hypogene  rocks  in  the  States  of 
Massachusetts  and  Connecticut,  strata  of  red  sandstone,  shale,  and 
conglomerate  are  found  occupying  an  area  more  than  150  miles  in 
length  from  north  to  south,  and  about  5  to  10  miles  in  breadth,  the 
beds  dipping  to  the  eastward  at  angles  varying  from  5  to  50  degrees. 
The  extreme  inclination  of  50  degrees  is  rare,  and  only  observed  in 
the  neighbourhood  of  masses  of  trap  which  have  been  intruded  into 
the  red  sandstone  while  it  was  forming,  or  before  the  newer  parts  of 
the  deposit  had  been  completed.  Having  examined  this  series  of 
rocks  in  many  places,  I  feel  satisfied  that  they  were  formed  in  shallow 
water,  and  for  the  most  part  near  the  shore,  and  that  some  of  the 
beds  were  from  time  to  time  raised  above  the  level  of  .the  water,  and 
laid  dry,  while  a  newer  series,  composed  of  similar  sediment,  was 
forming.  The  red  flags  of  thin-bedded  sandstone  are  often  ripple- 
marked,  and  exhibit  on  their  under-sides  casts  of  cracks  formed  in 
the  underlying  red  and  green  shales.  These  last  must  have  shrunk 
by  drying  before  the  sand  was  spread  over  them.  On  some  shales  of 
the  finest  texture  impressions  of  rain-drops  may  be  seen,  and  casts  of 
them  in  the  incumbent  argillaceous  sandstones.  Having  observed 
similar  markings  produced  by  showers,  of  which  the  precise  date  was 
known,  on  the  recent  red  mud  of  the  Bay  of  Fundy,  and  casts  in 
relief  of  the  same  on  layers  of  dried  mud  thrown  down  by  subsequent 
tides  *,  I  feel  no  doubt  in  regard  to  the  origin  of  some  of  the  ancient 
Connecticut  impressions.  I  have  also  seen  on  the  mud-flats  of  the 
Bay  of  Fundy  the  footmarks  of  birds  (  Tringa  minuta),  which  daily 
run  along  the  borders  of  that  estuary  at  low  water,  and  which  I  have 
described  in  my  Travels,  j"  Similar  layers  of  red  mud,  now  hardemed 
and  compressed  into  shale,  are  laid  open  on  the  banks  of  the  Connec- 
ticut, and  retain  faithfully  the  impressions  and  casts  of  the  feet  of 
numerous  birds  and  reptiles  which  walked  over  them  at  the  time  when 
they  were  deposited,  probably  in  the  Triassic  Period. 

According  to  Professor  Hitchcock,  the  footprints  of  no  less  than 
thirty-two  species  of  bipeds,  and  twelve  of  quadrupeds,  have  been 
already  detected  in  these  rocks.  Thirty  of  these  are  believed  to  be 
those  of  birds,  four  of  lizards,  two  of  chelonians,  and  six  of  batrachians. 
The  tracks  have  been  found  in  more  than  twenty  places,  scattered 
through  an  extent  of  nearly  80  miles  from  north  to  south,  and  they  are 
repeated  through  a  succession  of  beds  attaining  at  some  points  a 
thickness  of  more  than  1000  feet,  which  may  have  been  thousands  of 
years  in  forming.  J 

As  considerable  scepticism  is  naturally  entertained  in  regard  to 

*  Principles  of  Geology,  9th  ed.  J  Hitchcock,  Mem.  of  Amer.  Acad. 
p.  203.  New  Ser.  vol.  iii.  p.  129. 

t  Travels  in  North  America,  vol.  ii. 
p.  168. 


CH.  XXII.] 


FOSSIL  FOOTPRINTS. 


349 


Fig.  443. 


the  nature  of  the  evidence  derived  from  footprints,  it  may  be  well  to 
enumerate  some  facts  respecting  them  on  which  the  faith  of  the  geo- 
logist may  rest.  When  I  visited  the  United  States  in  1842,  more 
than  2000  impressions  had  been  observed  by  Professor  Hitchcock*, 
in  the  district  alluded  to,  and  all  of  them  were  indented  on  the  upper 
surface  of  the  layers,  while  the  corresponding  casts,  standing  out  in 
relief,  were  always  on  the  lower  surfaces  or  planes  of  the  strata.  If 
we  follow  a  single  line  of  marks  we  find  them  uni- 
form in  size,  and  nearly  uniform  in  distance  from 
each  other,  the  toes  of  two  successive  footprints 
turning  alternately  right  and  left  (see  fig.  443.). 
Such  single  lines  indicate  a  biped;  and  there  is 
generally  such  a  deviation  from  a  straight  line,  in 
any  three  successive  prints,  as  we  remark  in  the 
tracks  left  by  birds.  There  is  also  a  striking  rela- 
tion between  the  distance  separating  two  footprints 
in  one  series  and  the  size  of  the  impressions;  in 
other  words,  an  obvious  proportion  between  the 
length  of  the  stride  and  the  dimension  of  the 
creature  which  walked  over  the  mud.  If  the  marks 
are  small,  they  may  be  half  an  inch  asunder;  if 
gigantic,  as,  for  example,  where  the  toes  are  20 
inches  long,  they  are  occasionally  4  feet  and  a  half 
apart.  The  bipedal  impressions  are  for  the  most 
part  trifid,  and  show  the  same  number  of  joints  as 
exist  in  the  feet  of  living  tridactylous  birds.  Now, 
such  birds  have  three  phalangeal  bones  for  the 
inner  toe,  four  for  the  middle,  and  five  for  the  outer 
one  (see  fig.  443.) ;  but  the  impression  of  the  ter- 
minal joint  is  that  of  the  nail  only.  The  fossil 
footprints  exhibit  regularly,  where  the  joints  are 
seen,  the  same  number ;  and  we  see  in  each  con- 
Footprints  of  a  bird,  tinuous  line  of  tracks  the  three-jointed  and  five- 
ieyfof  "the  Connec-  jointed  toes  placed  alternately  outwards,  first  on  the 
Seine.  (liem.Dof  <>ne  side  and  then  on  the  other.  In  some  specimens, 
184?.)' Acad<  vol>  1V'  besides  impressions  of  the  three  toes  in  front,  the 
rudiment  is  seen  of  the  fourth  toe  behind.  It  is 
not  often  that  the  matrix  has  been  fine  enough  to  retain  impres- 
sions of  the  integument  or  skin  of  the  foot k,  but  in  one  fine  specimen 
found  at  Turner's  Falls  on  the  Connecticut,  by  Dr.  Deane,  these 
markings  are  well  preserved,  and  have  been  recognized  by  Prof.  Owen 
as  resembling  the  skin  of  the  ostrich,  and  not  that  of  reptiles,  f  Much 
care  is  required  to  ascertain  the  precise  layer  of  a  laminated  rock  on 
which  an  animal  has  walked,  because  the  impression  usually  extends 
downwards  through  several  laminse ;  and  if  the  upper  layer  originally 


*  See  also  Mem.  Amer.  Ac.  vol.  iii. 
1848. 

t  This  specimen  was  in  the  late 
Dr.  Mantell's  museum,  and  indicated  a 


bird  of  a  size  intermediate  between  the 
small  and  the  largest  of  the  Connecticut 
species. 


350  FOSSIL   FOOTPRINTS  [Cn.  XXII. 

trodden  upon  is  wanting,  the  mark  of  one  or  more  joints,  or  even  in 
some  cases  an  entire  toe,  which  sank  less  deep  into  the  soft  ground, 
may  disappear,  and  yet  the  remainder  of  the  footprint  be  well 
defined. 

The  size  of  several  of  the  fossil  impressions  of  the  Connecticut  red 
sandstone  so  far  exceeds  that  of  any  living  ostrich,  that  naturalists  at 
first  were  extremely  adverse  to  the  opinion  of  their  having  been  made 
by  birds,  until  the  bones  and  almost  entire  skeleton  of  the  Dinornis 
and  of  other  feathered  giants  of  New  Zealand  were  discovered.  Their 
dimensions  have  at  least  destroyed  the  force  of  this  particular  ob- 
jection. The  magnitude  of  the  impressions  of  the  feet  of  a  heavy 
animal,  which  has  walked  on  suft  mud,  increases  for  some  distance 
below  the  surface  originally  trodden  upon.  In  order,  therefore,  to 
guard  against  exaggeration,  the  casts  rather  than  the  mould  are 
relied  on.  These  casts  show  that  some  of  the  fossil  bipeds  had  feet 
four  times  as  large  as  the  ostrich,  but  not  perhaps  much  larger  than 
the  Dinornis. 

The  eggs  of  another  gigantic  bird,  called  JEpiornis,  which  has 
probably  been  exterminated  by  man,  have  recently  been  discovered 
in  an  alluvial  deposit  in  Madagascar.  The  egg  has  six  times  the 
capacity  of  that  of  the  ostrich ;  but,  judging  from  the  large  size  of 
the  egg  of  the  Apterix,  Prof.  Owen  does  not  believe  that  the  jEpiornis 
exceeded,  if  indeed  it  equalled,  the  Dinornis  in  stature. 

Among  the  supposed  bipedal  tracks,  a  single  distinct  example  only 
has  been  observed  of  feet  in  which  there  are  four  toes  directed  for- 
wards. In  this  case  a  series  of  four  footprints  is  seen,  each  22 
inches  long  and  12  wide,  with  joints  much  resembling  those  in  the 
toes  of  birds.  Professor  Agassiz  has  suggested  that  it  might  have 
belonged  to  a  gigantic  bipedal  batrachian.  Other  naturalists  have 
called  our  attention  to  the  fact,  that  some  quadrupeds,  when  walking, 
place  the  hind  foot  so  precisely  on  the  spot  just  quitted  by  the  fore 
foot,  as  to  produce  a  single  line  of  imprints,  like  those  of  a  biped ; 
and  Mr.  Waterhouse  Hawkins  has  remarked  that  certain  species  of 
frogs  and  lizards  in  Australia  have  the  two  outer  toes  so  slightly 
developed  and  so  much  raised  that  they  might  leave  tridactylous 
footprints  on  mud  and  sand.  Another  osteologist,  Dr.  Leidy,  in  the 
United  States,  observed  to  me  that  the  pterodactyl  was  a  bipedal 
reptile  approaching  the  bird  so  nearly  in  the  structure  and  shape  of 
its  wing-bones  and  tibiae,  that  some  of  these  last,  obtained  from  the 
Chalk  and  Wealden  in  England,  had  been  mistaken  by  the  highest 
authorities  for  true  birds'  bones.  May  not  the  foot,  therefore,  of  a 
pterodactyl  have  equally  resembled  that  of  a  bird  ?  Be  this  as  it 
may,  the  greater  number  of  the  American  impressions  agree  so 
precisely  in  form  and  size  with  the  footmarks  of  known  living 
birds,  especially  with  those  of  waders,  that  we  shall  act  most  in 
accordance  with  known  analogies  by  referring  most  of  them  at 
present  to  feathered,  rather  than  to  featherless  bipeds. 

No  bones  have  as  yet  been  met  with,  whether  of  pterodactyl  or 
bird,  in  the  rocks  of  the  Connecticut,  but  there  are  numerous  copro- 


CH.  XXII.]      IN   THE   VALLEY   OP    THE    CONNECTICUT.  351 

lites  ;  and  an  ingenious  argument  has  been  derived  by  Dr.  Dana  from 
the  analysis  of  these  bodies,  and  the  proportion  they  contain  of  uric 
acid,  phosphate  of  lime,  carbonate  of  lime,  and  organic  matter,  to 
show  that,  like  guano,  they  are  the  droppings  of  birds,  rather  than  of 
reptiles. 

Some  of  the  quadrupedal  footprints  which  accompany  those  of  birds 
are  analogous  to  European  Cheirotheria,  and  with  a  similar  dispro- 
portion between  the  hind  and  fore  feet.  Others  resemble  that  re- 
markable reptile,  the  Rhyncosaurus  of  the  English  Trias,  a  creature 
having  some  relation  in  its  osteology  both  to  chelonians  and  birds. 
Other  imprints,  again,  are  like  those  of  turtles. 

Mr.  Darwin,  in  his  "  Journal  of  a  Voyage  in  the  Beagle,"  informs  us 
that  the  "  South  American  ostriches,  although  they  live  on  vegetable 
matter,  such  as  roots  and  grass,  are  repeatedly  seen  at  Bahia  Blanca 
(lat.  39°  S.),  on  the  coast  of  Buenos  Ayres,  coming  down  at  low 
water  to  the  extensive  mud-banks  which  are  then  dry,  for  the  sake, 
as  the  Gauchos  say,  of  feeding  on  small  fish."  They  readily  take  to 
the  water,  and  have  been  seen  at  the  bay  of  San  Bias,  and  at  Port 
Valdez,  in  Patagonia,  swimming  from  island  to  island.*  It  is  there- 
fore evident,  that  in  our  times  a  South  American  mud-bank  might 
be  trodden  simultaneously  by  ostriches,  alligators,  tortoises,  and 
frogs ;  and  the  impressions  left,  in  the  nineteenth  century,  by  the 
feet  of  these  various  tribes  of  animals,  would  not  differ  from  each 
other  more  entirely  than  do  those  attributed  to  birds,  saurians, 
chelonians,  and  batrachians  in  the  rocks  of  the  Connecticut. 

To  determine  the  exact  age  of  the  red  sandstone  and  shale  con- 
taining these  ancient  footprints  in  the  United  States,  is  not  possible 
at  present.  No  fossil  shells  have  yet  been  found  in  the  deposit,  nor 
plants  in  a  determinable  state.  The  fossil  fish  are  numerous  and 
very  perfect ;  but  they  are  of  a  peculiar  type,  which  was  originally 
referred  to  the  genus  Palceoniscus,  but  has  since,  with  propriety, 
been  ascribed,  by  Sir  Philip  Egerton,  to  a  new  genus.  To  this  he 
has  given  the  name  of  Ischypterus,  from  the  great  size  and  strength 
of  the  fulcral  rays  of  the  dorsal  fin  (from  to-^ug,  strength,  and  Trrepov, 
a  fin).  They  differ  from  Palceoniscus,  as  Mr.  Redfield  first  pointed 
out,  by  having  the  vertebral  column  prolonged  to  a  more  limited 
extent  into  the  upper  lobe  of  the  tail,  or,  in  the  language  of  M. 
Agassiz,  they  are  less  heterocercal.  The  teeth  also,  according  to  Sir 
P.  Egerton,  who,  in  1844,  examined  for  me  a  fine  series  of  specimens 
which  I  procured  at  Durham,  Connecticut,  differ  from  those  of 
Palceoniscus  in  being  strong  and  conical. 

That  the  sandstones  containing  these  fish  are  of  older  date  than 
the  strata  containing  coal,  before  described  (p.  331.)  as  occurring  near 
Richmond  in  Virginia,  is  highly  probable.  These  were  shown  to  be 
as  old  at  least  as  the  oolite  and  lias.  The  higher  antiquity  of  the 
Connecticut  beds  cannot  be  proved  by  direct  superposition,  but  may 
be  presumed  from  the  general  structure  of  the  country.  That 

*  Journal  of  Voyage  of  Beagle,  &c.  2d  edition,  p.  89.  1845. 


352  ANTIQUITY   OF   CONNECTICUT   BEDS.  [Cn.  XXII. 

structure  proves  them  to  be  newer  than  the  movements  to  which  the 
Appalachian  or  Alleghany  chain  owes  its  flexures,  and  this  chain 
includes  the  ancient  coal-formation  among  its  contorted  rocks.  The 
unconformable  position  of  this  New  Red  with  ornithichnites  on  the 
edges  of  the  inclined  primary  or  paleozoic  rocks  of  the  Appalachians 
is  seen  at  4.  of  the  section,  fig.  505.  p.  392.  The  absence  of  fish  with 
decidedly  heterocercal  tails  may  afford  an  argument  against  the 
Permian  age  of  the  formation ;  and  the  opinion  that  the  red  sandstone 
is  triassic,  seems,  on  the  whole,  the  best  that  we  can  embrace  in  the 
present  state  of  our  knowledge. 


CH.  XXIII.J      DIVISION   OF   THE   PEKMIAN   GROUP.  353 


CHAPTER  XXIU. 

PERMIAN   OR  MAGNESIAN  LIMESTONE   GROUP. 

Fossils  of  Magnesian  Limestone  and  Lower  New  Red  distinct  from  the  Triassic  — 
Term  Permian  —  English  and  German  equivalents  — Marine  shells  and  corals  of 
English  Magnesian  limestone  —  Palaeoniscus  and  other  fish  of  the  marl-slate — 
Thecodont  Saurians  of  dolomitic  conglomerate  of  Bristol — Zechstein  and  Koth- 
liegendes  of  Thuringia — Permian  Flora — Its  generic  affinity  to  the  Carboni- 
ferous—  Psaronites  or  tree-ferns. 

WHEN  the  use  of  the  term  "Poikilitic"  was  explained  in  the  last 
chapter,  I  stated,  that  in  some  parts  of  England  it  is  scarcely  possible 
to  separate  the  red  marls  and  sandstones  so  called  (originally  named 
"  the  New  Red")  into  two  distinct  geological  systems.  Nevertheless, 
the  progress  of  investigation,  and  a  careful  comparison  of  English 
rocks  between  the  lias  and  the  coal  with  those  occupying  a  similar 
geological  position  in  Germany  and  Russia,  have  enabled  geologists 
to  divide  the  Poikilitic  formation ;  and  has  even  shown  that  the 
lowermost  of  the  two  divisions  is  more  closely  connected,  by  its  fossil 
remains,  with  the  carboniferous  group  than  with  the  trias.  If, 
therefore,  we  are  to  draw  a  line  between  the  secondary  and  primary 
fossiliferous  strata,  as  between  the  tertiary  and  secondary,  it  must 
run  through  the  middle  of  what  was  once  called  the  "  New  Red,"  or 
Poikilitic  group.  The  inferior  half  of  this  group  will  rank  as 
Primary  or  Paleozoic,  while  its  upper  member  will  form  the  base  of 
the  Secondary  series.  For  the  lower,  or  Magnesian  Limestone  di- 
vision of  English  geologists,  Sir  R.  Murchison  proposed,  in  1841,  the 
name  of  Permian,  from  Perm,  a  Russian  government  where  these 
strata  are  more  extensively  developed  than  elsewhere,  occupying  an 
area  twice  the  size  of  France,  and  containing  an  abundant  and  varied 
suite  of  fossils. 

Prof.  King,  in  his  valuable  monograph*  of  the  Permian  fossils  of 
England,  has  given  a  table  of  the  following  six  members  of  the  Per- 
mian system  of  the  north  of  England,  with  what  he  conceives  to  be 
the  corresponding  formations  in  Thuringia. 

North  of  England.  Thuringia. 

1.  Crystalline  or  concretionary,  and         1.  Stinkstein. 

non-crystalline  limestone. 

2.  Brecciated  and  pseudo-brecciated        2.  Kauchwacke. 

limestone. 

3.  Fossiliferous  limestone.  3.  Dolomite,  or  Upper  Zechstein. 

4.  Compact  limestone.  4.  Zechstein,  or  Lower  Zechstein. 

5.  Marl-slate.  5.  Mergel-schiefer,  or  Kupferschiefer. 

6.  Inferior  sandstones  of  various  co-        6.  Rothliegendes. 

lours. 

*  Palseontographical  Society,  1850,  London. 
A  A 


354  PERMIAN   LIMESTONES.  [Cn.  XXIII. 

I  shall  proceed,  therefore,  to  treat  briefly  of  these  subdivisions, 
beginning  with  the  highest,  and  referring  the  reader,  for  a  fuller 
description  of  the  lithological  character  of  the  whole  group,  as  it 
occurs  in  the  north  of  England,  to  a  valuable  memoir  by  Professor 
Sedgwick,  published  in  1835.* 

Crystalline  or  concretionary  limestone  (No.  1.).  —  This  formation 
is  seen  upon  the  coast  of  Durham  and  Yorkshire,  between  the  Wear 
and  the  Tees.  Among  its  characteristic  fossils  are  Schizodus  Schlo- 
theimi  (fig.  444.)  and  Mytilus  septifer  (fig.  446.). 


Fig.  444. 


Fig.  445. 


Fig.  446. 


Schixodns  Schlotheimi,  Geinitz. 
Crystalline  limestone,  Permian. 


The  hinge  of  Schizodus 

truncatus,  King. 

Permian. 


Mytilus  septifer,  King. 
Syn.  Modiola  acuminata, 

James  Sow. 

Permian  crystalline  lime- 
stone. 


These  shells  occur  at  Hartlepool  and  Sunderland,  where  the  rock 
assumes  an  oolitic  and  botroidal  character.  Some  of  the  beds  in  this 
division  are  ripple -marked ;  and  Mr.  King  imagines  that  the  absence 
of  corals  and  the  character  of  the  shells  indicate  shallow  water.  In 
some  parts  of  the  coast  of  Durham,  where  the  rock  is  not  crystalline, 
it  contains  as  much  as  forty-four  per  cent,  of  carbonate  of  magnesia, 
mixed  with  carbonate  of  lime.  In  other  places, — for  it  is  extremely 
variable  in  structure,  —  it  consists  chiefly  of  carbonate  of  lime,  and 
has  concreted  into  globular  and  hemispherical  masses,  varying  from 
the  size  of  a  marble  to  that  of  a  cannon-ball,  and  radiating  from  the 
centre.  Occasionally  earthy  and  pulverulent  beds  pass  into  compact 
limestone  or  hard  granular  dolomite.  The  stratification  is  very 
irregular,  in  some  places  well-defined,  in  others  obliterated  by  the 
concretionary  action  which  has  re-arranged  the  materials  of  the  rocks 
subsequently  to  their  original  deposition.  Examples  of  this  are  seen 
at  Pontefract  and  Ripon  in  Yorkshire. 

The  brecciated  limestone  (No.  2.)  contains  no  fragments  of  foreign 
rocks,  but  seems  composed  of  the  breaking-up  of  the  Permian  lime- 
stone itself,  about  the  time  of  its  consolidation.  Some  of  the  angular 
masses  in  Tynemouth  Cliff  are  2  feet  in  diameter.  This  breccia 
is  considered  by  Professor  Sedgwick  as  one  of  the  forms  of  the 
preceding  limestone,  No.  1.,  rather  than  as  regularly  underlying  it. 
The  fragments  are  angular  and  never  water-worn,  and  appear  to 
have  been  re-cemented  on  the  spot  where  they  were  formed.  It  is, 
therefore,  suggested  that  they  may  have  been  due  to  those  internal 
movements  of  the  mass  which  produced  the  concretionary  structure  ; 
but  the  subject  is  very  obscure,  and  after  studying  the  phenomenon 
in  the  Marston  Rocks,  on  the  coast  of  Durham,  I  found  it  impossible 


*  Trans.  Geol.  Soc.  Lond.,  Second  Series,  vol.  iii.  p.  37. 


CH.  XXIII.  J          PERMIAN   COMPACT   LIMESTONES. 


355 


to  form  any  positive  opinion  on  the  subject.  The  well-known  brec- 
ciated  limestones  of  the  Pyrenees  appeared  to  me  to  present  the 
nearest  analogy,  but  on  a  much  smaller  scale. 

The  fossiliferous  limestone  (No.  3.)  is  regarded  by  Mr.  King  as  'a 
deep-water  formation,  from  the  numerous  delicate  bryozoa  which  it 
includes.  One  of  these,  Fenestella  retiformis  (fig.  447.),  is  a  very 

Fig.  447. 


a.  Fenestella  relfformis,  Schlot.  sp. 

Syu.  Gorgoma  injundibuliformis,  Goldf.;  Reteporaflustracea,  Phillips. 
b.  Part  of  the  same  highly  magnified. 

Magnesian  limestone,  Humbleton  Hill,  near  Sunderland.* 

variable  species,  and  has  received  many  different  names.  It  some- 
times attains  a  large  size,  measuring  8  inches  in  width.  The  same 
zoophyte,  or  rather  mollusk,  with  several  other  British  species,  is 
also  found  abundantly  in  the  Permian  of  Germany. 

Shells  of  the  genera  Productus  (fig.  448.)  and  Strophalosia  (the 
latter  an  allied  form  with  teeth  in  the  hinge),  which  do  not  occur  in 


Fig.  448. 


Fig.  449. 


Prodnctus  horrfdus,  Sowerby 

(including  P.  calvus,  Sow.) 

Sunderland  and  Durham,  in  Magnesian 

Limestone;    Zechstein  and    Kupfer- 

schieier,  Germany. 


Spirffer  vndulalus,  Sow.  Min.  Con. 
Syn.  Triogonotreta  undulala,  King's 

Monogr. 
Magnesian  Limestone. 


strata  newer  than  the  Permian,  are  abundant  in  this  division  of  the 
series  in  the  ordinary  yellow  magnesian  limestone.  They  are  accom- 
panie'd  by  certain  species  of  Spirifer  (fig.  449.),  and  other  brachiopoda 
of  the  true  primary  or  paleozoic  type.  Some  of  this  same  tribe  of 
shells,  such  as  Athyris  Roissyi,  allied  to  Terebratula,  are  specifically 
the  same  as  fossils  of  the  carboniferous  rocks.  Avicula,  Area,  and 
Schizodus  (see  above,  figs.  444,  445,  446.),  and  other  lamellibran- 
chiate  bivalves,  are  abundant,  but  spiral  univalves  are  very  rare. 

The  compact  limestone  (No.  4.)  also  contains  organic  remains, 
especially  bryozoa,  and  is  intimately  connected  with  the  preceding. 


King's  Monograph,  pi.  2. 

AA   2 


356 


FOSSIL   FISH   OF   PERMIAN   MARL-SLATE.      [Cn.  XXIII. 


Beneath  it  lies  the  marl-slate  (No.  5.),  which  consists  of  hard,  cal- 
careous shales,  marl-slate,  and  thin-bedded  limestones.  At  East 
Thickley,  in  Durham,  where  it  is  thirty  feet  thick,  this  slate  has 
yielded  many  fine  specimens  of  fossil  fish  of  the  genera  Pal&oniscus, 
Pygopterus,  Ccelacanthus,  and  Platysomus,  genera  which  are  all 
found  in  the  coal-measures  of  the  carboniferous  epoch,  and  which 
therefore,  says  Mr.  King,  probably  lived  at  no  great  distance  from 
the  shore.  But  the  Permian  species  are  peculiar,  and,  for  the  most 
part,  identical  with  those  found  in  the  marl-slate  or  copper-slate  of 
Thuringia. 

Fig.  450. 


Restored  outline  of  a  fish  of  the  genus  Paleeoniscus,  Agass. 
PalcBothrissum,  Blainville. 

The  PalcBoniscus  above  mentioned  belongs  to  that  division  of 
fishes  which  M.  Agassiz  has  called  "  Heterocercal,"  which  have  their 
tails  unequally  bilobate,  like  the  recent  shark  and  sturgeon,  and  the 
vertebral  column  running  along  the  upper  caudal  lobe.  (See  fig. 
451.)  The  "Homocercal"  fish,  which  comprise  almost  all  the 


Fig.  451. 


Fig.  452. 


Shad.  (Clupea,  Herring  tribe.) 
Homocercal. 


8000  species  at  present  known  in  the  living  creation,  have  the  tail- 
fin  either  single  or  equally  divided ;  and  the  vertebral  column  stops 
short,  and  is  not  prolonged  into  either  lobe.  (See  fig.  452.) 

Now  it  is  a  singular  fact,  first  pointed  out  by  Agassiz,  that  the 
heterocercal  form,  which  is  confined  to  a  small  number  of  genera  in 
the  existing  creation,  is  universal  in  the  Magnesian  limestone,  and 
all  the  more  ancient  formations.  It  characterizes  the  earlier  periods 
of  the  earth's  history,  when  the  organization  of  fishes  made  a  greater 
approach  to  that  of  saurian  reptiles  than  at  later  epochs.  In  all  the 
strata  above  the  Magnesian  limestone  the  homocercal  tail  pre- 
dominates. 

A  full  description  has  been  given  by  Sir  Philip  Egerton  of  the 


CH.  XXIII.] 


DOLOMITIC    CONGLOMERATE. 


357 


species  of  fish  characteristic  of  the  marl-slate,  in  Prof.  King's  mono- 
graph before  referred  to,  where  figures  of  the  ichthyolites,  which  are 
very  entire  and  well  preserved,  will  be  found.  Even  a  single  scale 
is  usually  so  characteristically  marked  as  to  indicate  the  genus,  and 
sometimes  even  the  particular  species.  They  are  often  scattered 
through  the  beds  singly,  and  may  be  useful  to  a  geologist  in  de- 
termining the  age  of  the  rock. 


Fig.  453. 


Scales  of  fish.    Magnesian  limestone. 
Fig.  454.  Fig.  455. 


Fig.  456. 


Fig.  453.  PaUeoniscua  comptus,  Agassiz.     Scale  magnified.    Marl-slate. 
Fig.  454.  PalcBoniscus  elegans,  Sedg.     Under  surface  of  scale  magnified.    Marl-slate. 
Fig.  455.  Palceoniscus  glaphyrus,  Ag.    Under  surface  of  scale  magnified.     Marl-slate. 
Fig.  456.  Ccelacanlhus  granulatus,  Ag.    Granulated  surface  of  scale  magnified.    Marl-slate. 


Fig.  457. 


Fig.  458. 


Pygopterus  mandibularis,  Ag.    Marl-slate. 

«.  Outside  of  scale  magnified. 
b.  Under  surface  of  same. 


Acrolepis  Sedgwickii,  Ag. 

Outside  of  scale  magnified. 

Marl-slate. 


The  inferior  sandstones  (No.  6.  Tab.  p.  353.),  which  lie  beneath 
the  marl-slate,  consist  of  sandstone  and  sand,  separating  the  mag- 
nesian  limestone  from  the  coal,  in  Yorkshire  and  Durham.  In  some 
instances,  red  marl  and  gypsum  have  been  found  associated  with  these 
beds.  They  have  been  classed  with  the  magnesian  limestone  by 
Professor  Sedgwick,  as  being  nearly  co-extensive  with  it  in  geogra- 
phical range,  though  their  relations  are  very  obscure.  In  some 
regions  we  find  it  stated  that  the  imbedded  plants  are  all  specifically 
identical  with  those  of  the  carboniferous  series ;  and,  if  so,  they 
probably  belong  to  that  epoch  ;  for  the  true  Permian  flora  appears, 
from  the  researches  of  MM.  Murchison  and  de  Verneuil  in  Russia, 
and  of  Colonel  von  Gutbier  in  Saxony,  to  be,  with  few  exceptions, 
distinct  from  that  of  the  coal  (see  p.  359.). 

Dolomitic  conglomerate  of  Bristol. — Near  Bristol,  in  Somersetshire, 
and  in  other  counties  bordering  the  Severn,  the  unconformable  beds  of 
the  Lower  New  Red,  resting  immediately  upon  the  Coal-measures, 
consist  of  a  conglomerate  called  "  dolomitic,"  because  the  pebbles  of 
older  rocks  are  cemented  together  by  a  red  or  yellow  base  of  dolomite 

AA  3 


358  THECODOXT   SAURIANS.  [Cn.  XXIII. 

or  magnesian  limestone.  This  conglomerate  or  breccia,  for  the  im- 
bedded fragments  are  sometimes  angular,  occurs  in  patches  over  the 
whole  of  the  downs  near  Bristol,  filling  up  the  hollows  and  irregu- 
larities in  the  mountain  limestone,  and  being  principally  composed 
at  every  spot  of  the  debris  of  those  rocks  on  which  it  immediately 
rests.  At  one  point  we  find  pieces  of  coal-shale,  in  another  of 
mountain  limestone,  recognizable  by  its  peculiar  shells  and  zoophytes. 
Fractured  bones,  also,  and  teeth  of  saurians  are  dispersed  through 
some  parts  of  the  breccia. 

These  saurians  (which  until  the  discovery  of  the  Archegosaurus 
in  the  coal  were  the  most  ancient  examples  of  fossil  reptiles)  are  all 
distinguished  by  having  the  teeth  implanted  deeply  in  the  jaw-bone, 
and  in  distinct  sockets,  instead  of  being  soldered,  as  in  frogs,  to  a 
simple  alveolar  parapet.  In  the  dolomitic  conglomerate  near  Bristol 
the  remains  of  species  of  two  genera  have  been  found,  called  Theco- 
dontosaurus  and  Palceosaurus  by  Dr.  Riley  and  Mr.  Stutchbury  * ; 
the  teeth  of  which  are  conical,  compressed,  and  with  finely  serrated 
edges  (figs.  459  and  460.). 

Teeth  of  Saurians.    Dolomitic  conglomerate  ;  Redland,  near  Bristol.' 
Fig.  459.  Fig.  460. 


Tooth  of  Palesosaurus  (flf    M     Tooth  of  Thecodontosaurus, 

platyodon,  nat.  size.  fft  3  times  magnified. 


Sir  Henry  de  la  Beche  has  shown  that,  in  consequence  of  the 
isolated  position  of  the  breccia  containing  these  fossils,  it  is  very 
difficult  to  determine  to  what  precise  part  of  the  Poikilitic  series  they 
belong.^  Some  observers  suspect  them  to  be  triassic ;  but,  until  the 
evidence  in  support  of  that  view  is  more  conclusive,  we  may  con- 
tinue to  hold  the  opinion  of  their  original  discoverers. 

In  Russia,  also,  Thecodont  saurians  of  several  genera  occur,  in 
beds  of  the  Permian  age,  while  others,  named  Protorosaurus,  are  met 
with  in  the  Zechstein  of  Thuringia.  This  family  of  reptiles  is  allied 
to  the  living  monitor,  and  its  appearance  in  a  primary  or  paleozoic 
formation,  observes  Prof.  Owen,  is  opposed  to  the  doctrine  of  the 
progressive  development  of  reptiles  from  fish,  or  from  simpler  to  more 
complex  forms ;  for,  if  they  existed  at  the  present  day,  these  monitors 
would  take  rank  at  the  head  of  the  Lacertian  order.  J 

We  learn  from  the  writings  of  Sir  R.  Murchison  §  that  in  Russia 
the  Permian  rocks  are  composed  of  white  limestone,  with  gypsum  and 

*  Geol.  Trans.,  Second  Series,  vol.  v.  $  Owen,  Report  on  Reptiles,  British 

p.  349.,  plate  29.,  figures  2.  and  5.  Assoc.,  Eleventh  Meeting,  1841,  p.  197. 

•j-  Memoirs  of  Geol.  Survey  of  Great  §  Russia  and  the  Ural  Mountains, 

Britain,  vol.  i.  p.  268.  1845  ;  and  Siluria,  ch.xii.  1854. 


CH.  XXIII.] 


PERMIAN   FLORA. 


359 


white  salt ;  and  of  red  and  green  grits,  occasionally  with  copper-ore ; 
also  magnesian  limestones,  marlstones,  and  conglomerates. 

The  country  of  Mansfeld,  in  Thuringia,  may  be  called  the  classic 
ground  of  the  Lower  New  Red,  or  Magnesian  Limestone,  or  Permian 
formation,  on  the  Continent.  It  consists  there  principally  of,  first, 
the  Zechstein,  corresponding  to  the  upper  portion  of  our  English 
series ;  and,  secondly,  the  marl-slate,  with  fish  of  species  identical 
with  those  of  the  bed  so  called  in  Durham.  This  slaty  marlstone  is 
richly  impregnated  with  copper-pyrites,  for  which  it  is  extensively 
worked.  Magnesian  limestone,  gypsum,  and  rock-salt  occur  among 
the  superior  strata  of  this  group.  At  its  base  lies  the  Rothliegendes, 
supposed  to  correspond  with  the  Inferior  or  Lower  New  Red  Sand- 
stone above  mentioned,  which  occupies  a  similar  place  in  England 
between  the  marl-slate  and  coal.  Its  local  name  of  "  Rothliegendes," 
red-Iyer,  or  "  Roth-todt-liegendes,"  red-dead-Iyer,  was  given  by  the 
workmen  in  the  German  mines  from  its  red  colour,  and  because  the 
copper  has  died  out  when  they  reach  this  rock,  which  is  not  metal- 
liferous. It  is,  in  fact,  a  great  deposit  of  red  sandstone  and  con- 
glomerate, with  associated  porphyry,  basaltic  trap,  and  amygdaloid. 

Permian  Flora.  —  We  learn  from  the  recent  investigation  of 
Colonel  von  Gutbier,  that  in  the  Permian  rocks  of  Saxony  no  less 
than  sixty  species  of  fossil  plants  have  been  met  with,  forty  of  which 


Fig.  461. 


Fig.  462. 


Walchia  piniformis,  Sternb.    Permian,  Saxony.    (Gutbier,  pi.  x.) 
a.  branch.       6.  twig  of  the  same.       c.  leaf  magnified. 

have  not  yet  been  found  elsewhere.  Two  or  three  of  these,  as  Cala- 
mites  gigas,  Sphenopteris  erosa,  and  S.  lobata,  are  also  met  with  in 
the  government  of  Perm  in  Russia.  Seven  others,  and 
among  them  Neuropteris  Loshii,  Pecopteris  arbor  escens, 
and  P.  similis,  with  several  species  of  Walchia  (see 
fig.  461.),  a  genus  of  Conifers,  called  Lycopodites  by 
some  authors,  are  common  to  the  coal-measures. 

Among    the    genera   also    enumerated    by    Colonel 
rpon  ot-  Gutbier   are   the   fruit   called    Cardiocarpon  (see  fig. 

tontx.  Gutbier.  f  \  « 

Permian^&ixony.  462.),  Asteroptiyllites,  and  Annularia,  so  characteristic 

of  the  carboniferous  period ;  also  Lepidodendron,  which 

is   common   to   the   Permian   of  Saxony,    Thuringia,    and   Russia, 

A  A  4 


360 


PERMIAN   FLORA. 


[Cn.  XXIII. 


Fig.  463.. 


although  not  abundant.  Noeggerathia  (see  fig.  463.),  supposed  by 
A.  Brongniart  to  be  allied  to  Cycas,  is  another  link  between  the 
Permian  and  Carboniferous  vegetation.  Coni- 
ferae,  of  the  Araucarian  division,  also  occur; 
but  these  are  likewise  met  with  both  in  older 
and  newer  rocks.  The  plants  called  Sigillaria 
and  Stigmaria,  so  marked  a  feature  in  the  car- 
boniferous period,  are  as  yet  wanting. 

Among  the  remarkable  fossils  of  the  roth- 
liegendes,  or  lowest  part  of  the  Permian  in 
Saxony  and  Bohemia,  are  the  silicified  trunks  of 
tree-ferns  called  generically  Psaronius.  Their 
bark  was  surrounded  by  a  dense  mass  of  air- 
roots,  which  often  constituted  a  great  addition  to 
the  original  stem,  so  as  to  double  or  quadruple  its 
diameter.  The  same  remark  holds  good  in 
regard  to  certain  living  extra-tropical  arbores- 
cent ferns,  particularly  those  of  New  Zealand. 

Psaronites  are  also  found  in  the  uppermost 
coal  of  Autun  in  France,  and  in  the  upper  coal- 
measures  of  the  State  of  Ohio  in  the  United 
States,  but  specifically  different  from  those  of 
the  rothliegendes.  They  serve  to  connect  the 
Permian  flora  with  the  more  modern  portion  of 
the  preceding  or  carboniferous  group.  Upon  the  whole,  it  is  evident 
that  the  Permian  plants  approach  much  nearer  to  the  carboniferous 
flora  than  to  the  triassic ;  and  the  same  may  be  said  of  the  Permian 
fauna. 


Noeggerathia  cunetfolia* 
Ad.  Brongniart.* 


*  Murchison's  Kussia,  vol.  ii.  pi.  A.  fig.  3« 


CH.  XXIV.]  THE  CARBONIFEROUS  GROUP.  361 


CHAPTER  XXIV 

THE  COAL,  OR  CARBONIFEROUS  GROUP. 

Carboniferous  strata  in  the  south-west  of  England  —  Superposition  of  Coal-measures 
to  Mountain  limestone  —  Departure  from  this  type  in  North  of  England  and 
Scotland  —  Carboniferous  series  in  Ireland  —  Section  in  South  Wales  —  Under- 
clays  with  Stigmaria  —  Carboniferous  Flora  —  Ferns,  Lepidodendra,  Equisetaceae, 
Calamites,  Asterophyllites,  Sigillariae,  Stigmatise  —  Coniferse  —  Sternbergia  — 
Trigonocarpon  —  Grade  of  Coniferse  in  the  Vegetable  Kingdom  —  Absence  of 
Angiosperms  —  Coal,  how  formed  —  Erect  fossil  trees  —  Farkfield  Colliery  — 
St.  Etienne  Coal-field  —  Oblique  trees  or  snags  —  Fossil  forests  in  Nova  Scotia  — 
Rain-prints  —  Purity  of  the  Coal  explained  —  Time  required  for  the  accumu- 
lation of  the  Coal-measures  —  Brackish-water  and  marine  strata  —  Crustaceans 
of  the  Coal  —  Origin  of  Clay-iron-stone. 

THE  next  group  which  we  meet  with  in  the  descending  order  is  the 
Carboniferous,  commonly  called  "The  Coal;"  because  it  contains 
many  beds  of  that  mineral,  in  a  more  or  less  pure  state,  interstratified 
with  sandstones,  shales,  and  limestones.  The  coal  itself,  even  in 
Great  Britain  and  Belgium,  where  it  is  most  abundant,  constitutes 
but  an  insignificant  portion  of  the  whole  mass.  In  the  north  of 
England,  for  example,  the  thickness  of  the  coal-bearing  strata  has 
been  estimated  by  Prof.  Phillips  at  3000  feet,  while  the  various  coal- 
seams,  20  or  30  in  number,  do  not  in  the  aggregate  exceed  60  feet. 

The  carboniferous  formation  assumes  various  characters  in  dif- 
ferent parts  even  of  the  British  Islands.  It  usually  comprises  two 
very  distinct  members  :  1st,  that  usually  called  the  Coal-measures,  of 
mixed  freshwater,  terrestrial,  and  marine  origin,  often  including 
seams  of  coal  ;  2dly,  that  named  in  England  the  Mountain  or  Car- 
boniferous Limestone,  of  purely  marine  origin,  and  containing  corals, 
shells,  and  encrinites. 

In  the  south-western  part  of  our  island,  in  Somersetshire  and  South 
Wales,  the  three  divisions  usually  spoken  of  by  English  geologists 
are: 

/Strata  of  shale,  sandstone,  and  grit,  with  occasional  seams 
\     of  coal,  from  600  to  12,000  feet  thick. 
f  A  coarse  quartzose  sandstone  passing  into  a  conglomerate, 
2.  Millstone-grit    <      sometimes  used  for  millstones,  with  beds  of  shale  ;  usually 
devoid  of  coal  ;  occasionally  above  600  feet  thick. 

1  calcareous  rock  containing  marine  shells  and  corals  ; 

devoid  of  coal  ;  thickness  variable,  sometimes  900  feet. 


I 
C 


The  millstone  -grit  may  be  considered  as  one  of  the  coal-sandstones 
of  coarser  texture  than  usual,  with  some  accompanying  shales,  in 
which  coal-plants  are  occasionally  found.  In  the  north  of  England 


362  COAL-MEASURES.  [Cn.  XXIV. 

some  bands  of  limestone,  with  pectens,  oysters,  and  other  marine  shells, 
occur  in  this  grit,  just  as  in  the  regular  coal-measures,  and  even  a 
few  seams  of  coal.  I  shall  treat,  therefore,  of  the  whole  group  as 
consisting  of  two  divisions  only,  the  Coal-measures  and  the  Moun- 
tain Limestone.  The  latter  is  found  in  the  southern  British  coal- 
fields, at  the  base  of  the  system,  or  immediately  in  contact  with  the 
subjacent  Old  Red  Sandstone ;  but  as  we  proceed  northwards  to 
Yorkshire  and  Northumberland  it  begins  to  alternate  with  true  coal- 
measures,  the  two  deposits  forming  together  a  series  of  strata  about 
1000  feet  in  thickness.  To  this  mixed  formation  succeeds  the  great 
mass  of  genuine  mountain  limestone.*  Farther  north,  in  the  Fife- 
shire  coal-field  in  Scotland,  we  observe  a  still  wider  departure  from 
the  type  of  the  south  of  England,  or  a  more  complete  intercalation  of 
dense  masses  of  marine  limestones  with  sandstones  and  shales  con- 
taining coal. 

In  Ireland  a  series  of  shales  and  slates,  constituting  the  base  of  the 
Mountain  Limestone,  attain  so  great  a  thickness,  often  upwards  of 
1000  feet,  as  to  be  classed  as  a  separate  division.  Under  these  slates 
is  a  Yellow  Sandstone,  also  considered  as  carboniferous  from  its 
marine  fossils,  although  passing  into  the  underlying  Devonian.  A 
similar  sandstone  of  much  less  thickness  occurs  in  the  same  position 
in  Gloucestershire  and  South  Wales. 

The  following  are  the  subdivisions  adopted  in  the  geological  map 
of  Ireland,  constructed  by  Mr.  Griffiths  :  — 

Thickness  in  Feet. 

1.  Coal-measures,  Upper  and  Lower       -  1000  to  2200 

2.  Millstone-grit  -       350  to  1800 

3.  Mountain  limestone,  Upper,  Middle  (or  Calp),  and 

Lower         -  -     1200  to  6400 

4.  Carboniferous  slate     -  -  -  700  to  1200 

5.  Yellow   sandstone   (of  Mayo,   &c.)  with   shales   and 

limestone    ------      400  to  2000 


COAL  -MEASURE  S. 

In  South  Wales  the  coal-measures  have  been  ascertained  by  actual 
measurement  to  attain  the  extraordinary  thickness  of  12,000  feet ;  the 
beds  throughout,  with  the  exception  of  the  coal  itself,  appearing  to 
have  been  formed  in  water  of  moderate  depth,  during  a  slow,  but  per- 
haps intermittent,  depression  of  the  ground,  in  a  region  to  which 
rivers  were  bringing  a  never-failing  supply  of  muddy  sediment  and 
sand.  The  same  area  was  sometimes  covered  with  vast  forests,  such 
as  we  see  in  the  deltas  of  great  rivers  in  warm  climates,  which  are 
liable  to  be  submerged  beneath  fresh  or  salt  water  should  the  ground 
sink  vertically  a  few  feet. 

In  one  section  near  Swansea,  in  South  Wales,  where  the  total 
thickness  of  strata  is  3246  feet,  we  learn  from  Sir  H.  De  la  Beche 
that  there  are  ten  principal  masses  of  sandstone.  One  of  these  is 

*  Sedgwick,  GeoL  Trans.,  Second  Series,  vol.  iv.;  and  Phillips,  Geol.  of  Yorksh. 
part  2. 


CH.  XXIV.]  CARBONIFEROUS   FLORA.  363 

500  feet  thick,  and  the  whole  of  them  make  together  a  thickness  of 
2125  feet.  They  are  separated  by  masses  of  shale,  varying  in  thickness 
from  10  to  50  feet.  The  intercalated  coal-beds,  sixteen  in  number, 
are  generally  from  1  to  5  feet  thick,  one  of  them,  which  has  two  or 
three  layers  of  clay  interposed,  attaining  9  feet.*  At  other  points  in 
the  same  coal-field  the  shales  predominate  over  the  sandstones.  The 
horizontal  extent  of  some  seams  of  coal  is  much  greater  than  that  of 
others,  but  they  all  present  one  characteristic  feature,  in  having,  each 
of  them,  what  is  called  its  underclay.  These  underclays,  co-extensive 
with  every  layer  of  coal,  consist  of  arenaceous  shale,  sometimes  called 
fire-stone,  because  it  can  be  made  into  bricks  which  stand  the  fire  of 
a  furnace.  They  vary  in  thickness  from  6  inches  to  more  than  10 
feet ;  and  Mr.  Logan  first  announced  to  the  scientific  world  in  1841 
that  they  were  regarded  by  the  colliers  in  South  Wales  as  an  essen- 
tial accompaniment  of  each  of  the  one  hundred  seams  of  coal  met 
with  in  their  coal-field.  They  are  said  to  form  the  floor  on  which 
the  coal  rests  ;  and  some  of  them  have  a  slight  admixture  of  carbona- 
ceous matter,  while  others  are  quite  blackened  by  it. 

All  of  them,  as  Mr.  Logan  pointed  out,  are  characterized  by 
inclosing  a  peculiar  species  of  fossil  vegetable  called  Stigmaria,  to 
the  exclusion  of  other  plants.  It  was  also  observed  that,  while  in  the 
overlying  shales  or  "roof"  of  the  coal,  ferns  and  trunks  of  trees 
abound  without  any  Stiffmaria,  and  are  flattened  and  compressed, 
those  singular  plants  of  the  underclay  very  often  retain  their  natural 
forms,  branching  freely,  and  sending  out  their  slender  leaf-like 
rootlets,  formerly  thought  to  be  leaves,  through  the  mud  in  all  di- 
rections. Several  species  of  Stigmaria  had  long  been  known  to 
botanists,  and  described  by  them,  before  their  position  under  each 
seam  of  coal  was  pointed  out,  and  before  their  true  nature  as  the 
roots  of  trees  was  recognized.  It  was  conjectured  that  they  might 
be  aquatic,  perhaps  floating  plants,  which  sometimes  extended  their 
branches  and  leaves  freely  in  fluid  mud,  and  which  were  finally  en- 
veloped in  the  same  mud. 

CARBONIFEROUS   FLORA. 

These  statements  will  suffice  to  convince  the  reader  that  we  cannot 
arrive  at  a  satisfactory  theory  of  the  origin  of  coal  until  we  under- 
stand the  true  nature  of  Stigmaria  ;  and  in  order  to  explain  what  is 
now  known  of  this  plant,  and  of  others  which  have  contributed  by 
their  decay  to  produce  coal,  it  will  be  necessary  to  offer  a  brief  pre- 
liminary sketch  of  the  whole  carboniferous  flora,  an  assemblage  of 
fossil  plants  with  which  we  are  better  acquainted  than  with  any  other 
which  flourished  antecedently  to  the  tertiary  epoch.  It  should  also 
be  marked  that  Goppert  has  ascertained  that  the  remains  of  every 
family  of  plants  scattered  through  the  coal-measures  are  sometimes 
met  with  in  the  pure  coal  itself,  a  fact  which  adds  greatly  to  the  geo- 
logical interest  attached  to  this  flora. 

*  Memoirs  of  Geol.  Survey,  vol.  i.  p.  195. 


364 


FERNS    OF    CARBONIFEROUS   PERIOD.       [Cn.  XXIV. 


Ferns.  —  The  number  of  species  of  carboniferous  plants  hitherto 
described  amounts,  according  to  M.  Ad.  Brongniart,  to  about  500. 
These  may  perhaps  be  a  fragment  only  of  the  entire  flora,  but  they 
are  enough  to  show  that  the  state  of  the  vegetable  world  was  then 
extremely  different  from  that  now  prevailing.  We  are  struck  at 
the  first  glance  with  the  similarity  of  many  of  the  ferns  to  those  now 
living,  and  the  dissimilarity  of  almost  all  the  other  fossils  except  the 


Fig.  464. 


Fig.  465. 


Pecopteris  lonchitica. 
(Foss.  Flo.  153.) 


a.  Sphenopteris  crenata. 

b.  Part  of  the  same, 


(Foss.  Flo.  101 .) 


magnified. 


Fig.  466. 


coniferse.  Among  the  ferns,  as  in  the 
case  of  Pecopteris  for  example  (fig.  464.), 
it  is  not  always  easy  to  decide  whether 
they  should  be  referred  to  different 
genera  from  those  established  for  the 
classification  of  living  species  ;  whereas, 
in  regard  to  most  of  the  other  contem-1 
porary  tribes,  with  the  exception  of  the 
coniferae,  it  is  often  difficult  to  guess  the 
family,  or  even  the  class,  to  which  they 
belong.  The  ferns  of  the  carboniferous 
period  are  generally  without  organs  of 
fructification,  but  in  some  specimens 
these  are  well  preserved.  In  the  general 
absence  of  such  characters,  they  have 
been  divided  into  genera  distinguished 
chiefly  ty  the  branching  of  the  fronds, 
and  the  way  in  which  the  veins  of  the  leaves  are  disposed.  The 
larger  portion  are  supposed  to  have  been  of  the  size  of  ordinary 


CH.  XXIV.]  FERNS  —  LEPIDODENDRON.  365 

European  ferns,  but  some  were  decidedly  arborescent,  especially  the 
group  called  Caulopteris,  by  Lindley,  and  the  Psaronius  of  the  upper 
or  newest  coal-measures,  before  alluded  to  (p.  360.). 

All  the  recent  tree-ferns  belong  to  one  tribe  (Polypodiacece),  and 
to  a  small  number  only  of  genera  in  that  tribe,  in  which  the  surface 
of  the  trunk  is  marked  with  scars,  or  cicatrices,  left  after  the  fall  of 
the  fronds.  These  scars  resemble  those  of  Caulopteris  (see  fig.  466.). 
No  less  than  250  ferns  have  already  been  obtained  from  the  coal- 
strata;  and,  even  if  we  make  some  reduction  on  the  ground  of 
varieties  which  have  been  mistaken,  in  the  absence  of  their  fructi- 
fication, for  species,  still  the  result  is  singular,  because  the  whole  of 
Europe  affords  at  present  no  more  than  60  indigenous  species. 

Fig.  468. 


Living  tree-ferns  of  different  genera.    (Ad.  Brong.) 

Fig.  467.    Tree-fern  from  Isle  of  Bourbon. 
Fig.  468.     Cyathea  glnuca,  Mauritius. 
Fig.  469.    Tree-fern  from  Brazil. 

Lepidodendron. — About  40  species  of  fossil  plants  of  the  Coal 
have  been  referred  to  this  genus.  They  consist  of  cylindrical  stems 
or  trunks,  covered  with  leaf-scars.  In  their  mode  of  branching,  they 
are  always  dichotomous  (see  fig.  471.).  They  are  considered  by 
Brongniart  and  Hooker  to  belong  to  the  Lycopodiacece,  plants  of 
this  family  bearing  cones,  with  similar  sporangia  and  spores 
(fig.  474.).  Most  of  them  grew  to  the  size  of  large  trees.  The 
figures  470 — 472.  represent  a  fossil  Lepidodendron,  49  feet  long,  found 
in  Jarrow  Colliery,  near  Newcastle,  lying  in  shale  parallel  to  the 
planes  of  stratification.  Fragments  of  others,  found  in  the  same 
shale,  indicate,  by  the  size  of  the  rhomboidal  scars  which  cover 
them,  a  still  greater  magnitude.  The  living  club-mosses,  of  which 
there  are  about  200  species,  are  abundant  in  tropical  climates,  where 
one  species  is  sometimes  met  with  attaining  a  height  of  3  feet.  They 
usually  creep  on  the  ground,  but  some  stand  erect,  as  the  L.  densum. 
from  New  Zealand  (fig.  473.). 


366 


Fig.  470. 


LEPIDODENDRON. 

Fig.  471. 


[CH.  XXIV. 


Lepidodendron  Sternbergii.    Coal-measures,  near  Newcastle. 

Fig.  470.  Branching  trunk,  49  feet  long,  supposed  to  have  belonged  to  L  Stern- 
bergii.   (Foss.  Flo.  203.) 

Fig.  471.  Branching  stem  with  bark  and  leaves  of  L.  Sternbergii.    (Foss.  Flo.  4.) 
Fig.  472.  Portion  of  same  nearer  the  root ;  natural  size.    (Ibid.) 


a.  Lycopodium  densum  /  banks  of  R.  Thames,  New  Zealand. 

b.  branch,  natural  size.  c.  part  of  same,  magnified. 

In  the  carboniferous  strata  of  Coalbrook  Dale,  and  in  many  other 
coal-fields,  elongated  cylindrical  bodies,  called  fossil  cones,  named 
Lepidostrobus  by  M.  Adolphe  Brongniart,  are  met  with.     (See  fig. 
474.)     They  often  form  the  nucleus  of  concretionary  balls  of  clay- 
Fig.  474. 


«.  Lepidostrobus  ornalus,  Brong.     Shropshire;  half  natural  size 

6.  Portion  of  a  section  showing  the  large  sporangia  in  their  natural  position,  and  each 

supported  by  its  bract  or  scale, 
c.  Spores  in  these  sporangia,  highly  magnified.    (Hooker,  Mem.   Geol.  Survey,  vol.  ii. 

part  2.  p.  440.) 

ironstone,  and  are  well  preserved,  exhibiting  a  conical  axis,  around 
which  a  great  quantity  of  scales  were  compactly  imbricated.  The 
opinion  of  M.  Brongniart  is  now  generally  adopted,  that  the  Lepi- 
dostrobus is  the  fruit  of  Lepidodendron  ;  indeed,  it  is  not  uncommon 


OH.  XXIV.] 


EQUISETACE.E  —  CALAMITES. 


367 


in  Coalbrook  Dale  and  elsewhere  to  find  these  strobili  or  fruits  termi- 
nating the  tip  of  a  branch  of  a  well  characterized  Lepidodendron. 

Equisetacece.  —  To  this  family  belong  two  fossil  species  of  the  Coal, 
one  called  Equisetum  infundibuliforme  by  Brongniart,  and  found  also 
in  Nova  Scotia,  which  has  sheaths,  regularly  toothed,  ribbed,  and 
overlapping  like  those  on  the  young  fertile  stems  of  Equisetum  flu- 
viatile.  It  was  much  larger  than  any  living  "  Horsetail. "  The 
Equisetum  giganteum,  discovered  by  Humboldt  and  Bonpland  in 
South  America,  attained  a  height  of  about  5  feet,  the  stem  being  an 
inch  in  diameter ;  but  more  recently  Gardner  has  met  with  one  in 
Brazil  15  feet  high,  and  Meyen  gives  the  height  of  E.  Bogotense  in 
Chili  as  15  to  20  feet. 

Calamites.  —  The  fossil  plants  so  called  were  originally  classed  by 
most  botanists  as  cryptogamous,  being  regarded  as  gigantic  Equiseta  ; 


Fig.  475. 


Fig.  476. 


Calamites  cann&formis,  Schlot. 
(Koss.  Flo.  79.)  Common  in 
English  coal. 


Calamites  Suckowii,  Brong.; 
natural  size.  Common  in 
coal  throughout  Europe. 


Fig.  477. 


for,  like  the  common  "  horsetail,"  they  usually  ex- 
hibit little  more  than  hollow  jointed  stems,  furrowed 
externally.  (See  figs.  475,  476,  477.) 

Mr.  Salter  stated  to  me  many  years  ago  his  con- 
viction that  the  calamite  as  frequently  represented 
by  paleontologists  was  in  an  inverted  position, 
and  that  the  conical  part  given  as  the  top  of  the 
stem  was  in  truth  the  root.  This  point  Mr.  Dawson 
and  I  had  opportunities  of  testing  in  Nova  Scotia, 
where  we  saw  many  erect  calamites,  having  their 
radical  termination  as  in  the  annexed  figure  (fig. 
477.).  The  scars,  from  which  whorls  of  vessels 
have  proceeded,  are  observed  at  the  upper,  not  the 
lower  end  of  each  joint  or  internode.*  The  speci- 
men, fig.  475.,  therefore,  is  no  doubt  the  lower  end  of 
the  plant,  and  I  have  therefore  reversed  its  position 
as  given  in  the  work  of  Lindley  and  Hutton. 

M.  Adolphe  Brongniart,  following  up  the  discoveries  of  Germar 

and  Corda,  has  shown  in  his  "  Genres  de  Vegetaux  Fossiles,"  1849, 

that  many  Calamites  cannot  belong  to  the  Equiseta,  nor  probably  to 

any  tribe  of  flowerless  plants.     He  conceives  that  they  are  more 

*  See  Dawson,  Geol.  Quart.  Journal,  1854,  vol.  x.  p.  35. 

*AA8 


Radical  termination 
of  a  Calamite.  Nova 
Scotia. 


368 


CALAMITES. 


[CH.  xxiv. 


nearly  allied  to  the  Gymnospermous  Dicotyledons.  They  possessed 
a  central  pith,  surrounded  by  a  ligneous  cylinder,  which  was  divided 
by  regular  medullary  rays.  This  cylinder  was  surrounded  in  turn 
by  a  thick  bark.  Of  fossil  stems  having  this  structure  Brongniart 
formed  his  genus  Calamodendron,  which  includes  many  species 
referred  by  Cotta,  Petzholdt,  and  Unger  to  the  genus  Calamitea. 
The  Calamodendron  is  described  as  smooth  externally,  its  pith  being 
articulated  and  marked  with  deep  external  vertical  stride,  agreeing 
in  short  with  what  geologists  commonly  call  a  Calamite.  Since  the 
appearance  of  Brongniart's  essay,  Mr.  E.  W.  Binney  has  made  many 
important  discoveries  on  the  same  subject  ;  and  Mr.  J.  S.  Dawes  has 
published  (Quart.  Journ.  Geol.  Soc.  Lond.  1851,  vol.  vii.  p.  196.) 

a  more  complete  account  of  this 
singular  fossil.  Their  views  have 
been  confirmed  by  Prof.  Wil- 
liamson of  Manchester,  who  has 
communicated  to  me  a  specimen, 
figured  in  the  annexed  cut  (fig. 
478.),  in  which  we  see  an  in- 
ternal pith  answering  in  cha- 
racter to  the  Calamodendron 
and  yet  having  outside  of  it  an- 


Fig. 478. 


other  jointed  cylinder  vertically 
grooved  on  its  outer  surface,  so 
that  in  the  same  stem  we  have 
one  calamite  enveloping  an- 
other. Yet  that  they  both 
formed  part  of  the  same  plant 
is  proved  by  the  following  cir- 
cumstances :  —  1st.  Near  each 

Portion  of  a  Calamite,  near  the  base,  showing  the   n~^n^n4.i^n  nft\*n  -nltl*     nA'    4-' 
external  cylinder,  connected  by  radiating  vessels   articulation  Ot  the  pith  radiating 
with  the  cast  ot  the  pith.     Its  position  inverted   cnnlrpc    arp    QPPTI    -fn  mrinAorl    anrl 

to  allow  the  light  to  enter  the  cavity.  spores  are  seen  to  proceed.  and 

Communicated  by  Prof.  w.  c.  wmiamson.      penetrate    the    ligneous    zone. 

One  complete  whorl  or  circle  of  these  radii  is  visible  in  the  annexed 
figure  near  the  bottom  of  the  hollow  cavity,  whilst  another  and 
superior  whorl  is  incomplete  ;  several  radii,  corresponding  to  the 
first,  remaining,  while  the  rest  have  been  broken  away,  their  place 
being  shown  by  scars  which  they  have  left.  2dly.  In  addition  to 
these  whorls,  called  medullary  by  Prof.  Williamson,  there  are  seen 
in  other  specimens  a  set  of  true  or  ordinary  medullary  rays.  3dly. 
The  woody  zone,  penetrated  both  by  the  spoke-like  vessels  before- 
mentioned  and  by  the  medullary  rays,  is  usually  reduced  to  brown 
carbonaceous  matter,  preserving  merely  a  tendency  to  break  in  longi- 
tudinal slips,  but  in  some  specimens  its  fibrous  tissue  is  retained,  and 
resembles  that  of  Dadoxylon.  4thly.  Outside  of  this  zone  again  is 
another  cylinder,  supposed  to  have  been  originally  a  thick  cellular 
bark,  nearly  equal  to  one-third  of  the  whole  stem  in  diameter,  grooved 
and  jointed  externally  like  the  pith. 

Jn  conclusion,  I  may  remark  that  these  discoveries  make  it  more 


CH.  XXIV.]  ASTEROPHYLLITES — SIGILLARIA.  369 

and  more  doubtful  to  what  family  the  greater  number  of  Calamites 
should  be  referred.  Their  internal  organization,  says  Prof.  Wil- 
liamson, was  very  peculiar;  for  while  they  exhibit  remarkable 
affinities  with  gymnospermous  dicotyledons,  the  arrangement  of 
their  tissues  differs  widely  from  that  of  all  known  forms  of  gymno- 
sperms. 

Aster ophyllites. —  The  graceful  plant  represented  in  the  annexed 
figure  is  supposed  by  M.  Brongniart  to  be  a  branch  of  the  Calamo- 
dendron,  and  he  infers  from  its  pith  and  medullary  rays  that  it  was 
dicotyledonous.  It  appears  to  have  been  allied,  by  the  nature  of  its 

Fig.  479. 


Aster  ophyllites  foliosa.    (Foss.  Flo.  25.)    Coal-measures,  Newcastle. 


tissue,  to  the  gymnogens,  and  to  Sigillaria.  But  under  the  head  of 
Asterophyllites  many  vegetable  fragments  have  been  grouped  which 
probably  belong  to  different  genera.  They  have,  in  short,  no  cha- 
racter in  common,  except  that  of  possessing  narrow,  verticillate, 
one-ribbed  leaves.  Dr.  Newberry,  of  Ohio,  has  discovered  in  the 
coal  of  that  country  fossil  stems  which  in  their  upper  part  bear 
wedge-shaped  leaves  corresponding  to  Sphenophyllum,  while  below 
the  leaves  are  stalk -like  and  capillary,  and  would  have  been  called 
Asterophyllites  if  found  detached.  From  this  he  infers  that  Spheno- 
phyllum  was  an  aquatic  plant,  the  superior  and  floating  leaves  of 
which  were  broad,  and  possessed  a  compound  nervation,  while  the 
inferior  or  submersed  leaves  were  linear  and  one-ribbed.  "  This 
supposition,"  he  adds,  "is  further  strengthened  by  the  extreme 
length  and  tenuity  of  the  branches  of  this  apparently  herbaceous 
plant,  which  would  seem  to  have  required  the  support  of  a  denser 
medium  than  air."* 

Sigillaria. — A  large  portion  of  the  trees  of  the  carboniferous 
period  belonged  to  this  genus,  of  which  about  thirty -five  species  are 
known.  The  structure,  both  internal  and  external,  was  very  pe- 
culiar, and,  with  reference  to  existing  types,  very  anomalous.  They 
were  formerly  referred,  by  M.  Ad.  Brongniart,  to  ferns,  which  they 
resemble  in  the  scalariform  texture  of  their  vessels,  and,  in  some 
degree,  in  the  form  of  the  cicatrices  left  by  the  base  of  the  leaf- 

*  Annals  of  Science,  Cleveland,  Ohio,  1853,  p.  97. 
B  B 


370 


SIGILLARIA    AND    STIGMARIA. 


[Cn.  XXIV. 


stalks  which  have  fallen  off  (see  fig.  480.).     But  with  these  points 
of  analogy  to  cryptogamia,  they  combine  an  internal  organization 
Fig.  480.  much  resembling  that  of  cycads,  and  some 

of  them  are  ascertained  to  have  had  long 
linear  leaves,  quite  unlike  those  of  ferns. 
They  grew  to  a  great  height,  from  30  to 
60,  or  even  70  feet,  with  regular  cylin- 
drical stems,  and  without  branches,  al- 
though some  species  were  dichotomous 
towards  the  top.  Their  fluted  trunks, 
from  1  to  5  feet  in  diameter,  appear  to 
have  decayed  more  rapidly  in  the  interior 
than  externally,  so  that  they  became 
hollow,  when  standing ;  and  when  thrown 
prostrate  on  the  mud,  they  were  squeezed 
down  and  flattened.  Hence,  we  find  the 
bark  of  the  two  opposite  sides  (now  con- 
verted into  bright  shining  coal)  to  con- 
stitute two  horizontal  layers,  one  upon 
the  other,  half  an  inch,  or  an  inch,  in  thickness.  These  same 
trunks,  when  they  are  placed  obliquely  or  vertically  to  the  planes 
of  stratification,  retain  their  original  rounded  form,  and  are  uncom- 
pressed, the  cylinder  of  bark  having  been  filled  with  sand,  which 
now  affords  a  cast  of  the  interior. 

Dr.  Hooker  still  inclines  to  the  belief  that  the  Sigillarice  may  have 
been  cryptogamous,  though  more  highly  developed  than  any  flower- 
less  plants  now  living.  The  scalariform  structure  of  their  vessels 
agrees  precisely  with  that  of  ferns. 

Stigmaria.  —  This  fossil,  the  importance  of  which  has  already  been 
pointed  out,  was  formerly  conjectured  to  be  an  aquatic  plant.  It  is 
now  ascertained  to  be  the  root  of  Sigillaria.  The  connection  of  the 
roots  with  the  stem,  previously  suspected,  on  botanical  grounds,  by 
Brongniart,  was  first  proved,  by  actual  contact,  in  the  Lancashire 
coal-field,  by  Mr.  Binney.  The  fact  has  lately  been  shown,  even 
more  distinctly,  by  Mr.  Richard  Brown,  in  his  description  of  the 

Fig.  4S1. 


Sigillaria  Icevigata,  Brong. 


Stigmaria  attached  to  a  trunk  of  Sigillaria* 

*  The  trunk  in  this  case  is  referred    markings  assumed  by  Sigillaria  near  its 
!>y  Mr.  Brown  to  Lepidodendron,  but  his    base, 
illustrations  seem  to  show  the    usual 


CH.  XXIV.] 


CONIFERS    OF    COAL    PERIOD. 


371 


Stigmarice  occurring  in  the  underclays  of  the  coal-seams  of  the 
Island  of  Cape  Breton,  in  Nova  Scotia. 

In  a  specimen  of  one  of  these,  represented  in  the  annexed  figure 
(fig.  481.),  the  spread  of  the  roots  was  16  feet,  and  some  of  them  sent 
out  rootlets,  in  all  directions,  into  the  surrounding  clay. 

In  the  sea-cliffs  of  the  South  Joggins  in  Nova  Scotia  I  examined 
several  erect  Sigillarice,  in  company  with  Mr.  Dawson,  and  we  found 
that  from  the  lower  extremities  of  the  trunk  they  sent  out  Stig- 
marice  as  roots.  All  the  stools  of  the  fossil  trees  dug  out  by  us 
divided  into  four  parts,  and  these  again  bifurcated,  forming  eight 
roots,  which  were  also  dichotomous  when  traceable  far  enough. 

The  manner  of  attachment  of  the  fibres  to  the  stem  resembles 
that  of  a  ball  and  socket  joint,  the  base  of  each  rootlet  being  con- 
cave, and  fitting  on  to  a  tubercle  (see  figs.  482.  and  483.).  Rows  of 

Fig.  483. 


Fig.  482. 


Surface  of  another  individual  of 
same  species,  showing  form  of 
tubercles.  (Fuss.  Flo.  34.) 


Stigmariaficoides,  Brong.    One  fourth  of  nat.  size.    (Foss.  Flo. 32.) 

these  tubercles  are  arranged  spirally  round  each  root,  which  has 
always  a  medullary  cavity  and  woody  texture,  much  resembling  that 
of  Sigillaria,  the  structure  of  the  vessels  being,  like  it,  scalariform. 

Conifer CB.  —  The  coniferous  trees  of  this  period  are  referred  to  five 
genera ;  the  woody  structure  of  some  of  them  showing  that  they  were 
allied  to  the  Araucarian  division  of  pines,  more  than  to  any  of  our 
common  European  firs.  Some  of  their  trunks  exceeded  44  feet  in 
height.  Many,  if  not  all  of  them,  seem  to  have  differed  from  living 
Coniferce  in  having  large  piths  ;  for  Professor  Williamson  has  demon- 
strated the  fossil  of  the  coal-measures  called  Sternbergia  to  be  the 
pith  of  these  trees,  or  rather  the  cast  of  cavities  formed  by  the 
shrinking  or  partial  absorption  of  the  original  medullary  axis  (see 
figs.  484.  and  485.).  This  peculiar  type  of  pith  is  observed  in  living 
plants  of  very  different  families,  such  as  the  common  Walnut  and 
the  White  Jasmine,  in  which  the  pith  becomes  so  reduced  as  simply 
to  form  a  thin  lining  of  the  medullary  cavity,  across  which  trans- 
verse plates  of  pith  extend  horizontally,  so  as  to  divide  the  cylin- 
drical hollow  into  discoid  interspaces.  When  these  last  have  been 
filled  up  with  inorganic  matter,  they  constitute  an  axis  to  which,  before 
their  true  nature  was  known,  the  provisional  name  of  Sternbergia 
(d,  d}  fifr.  484.)  was  given. 

B  B  2 


372 


CONIFERS    OF   THE   COAL   PERIOD.        [Cn.  XXIV. 

Fig.  484. 


Fig.  484.  Fragment  of  coniferous  wood,  Dadoxylon, 
Endlicher,  fractured  longitudinally ;  from  Coal- 
brook  Dale.  W.  C.  Williamson.* 

«.  bark. 

b.  woody  zone  or  fibre  (pleurenchyma). 

c.  medulla  or  pith.  , 

d.  cast  of  hoilow  pith,  or  "  Sternbergia." 


Magnified  portion  of  fig.  484. ;  transverse  section. 
c.  pith.  b,  b.  woody  fibre.  e>  e.  medullary  rays. 

In  the  above  specimen  the  structure  of  the  wood  (b,  figs.  484.  and 
485.)  is  coniferous,  and  the  fossil  is  referable  to  Endlicher's  fossil 
genus  Dadoxylon. 

The  fossil  named  Trigonocarpon  (figs.  486.  and  487.),  formerly 


Fig.  487. 


Fig.  486. 


Trigonocarpum  ovatum,  Lindley  and  Hutton. 
Peel  Quarry,  Lancashire. 


Trigonocarpum  olivceforme,  -Lindley,  with 
its  fleshy  envelope.  Felling  Colliery, 
Newcastle. 

supposed  to  be  the  fruit  of  a  palm,  may  now,  according  to  Dr. 
Hooker,  be  referred,  like  the  Sternbergia,  to  the  Conifers.  Its  geo- 
logical importance  is  great,  for  so  abundant  is  it  in  the  Coal 
Measures,  that  in  certain  localities  the  fruit  of  some  species  may  be 
procured  by  the  bushel ;  nor  is  there  any  part  of  the  formation  where 
they  do  not  occur,  except  the  underclays  and  limestone.  The  sand- 
stone, ironstone,  shales,  and  coal  itself,  all  contain  them.  Mr.  Binney 

Manchester  Philos.  Mem.  vol.  ix.  1851. 


CH.  XXIV.]        GRADE   OF   THE   CARBONIFEROUS   FLORA.         373 

has  at  length  found  in  the  clay-ironstone  of  Lancashire  several 
specimens  displaying  structure,  and  from  these,  says  Dr.  Hooker,  we 
learn  that  the  Trigonocarpon  belonged  to  that  large  section  of  existing 
coniferous  plants  which  bear  fleshy  solitary  fruits,  and  not  cones. 
It  resembled  very  closely  the  fruit  of  the  Chinese  genus  Salisburia, 
one  of  the  Yew  tribe,  or  Taxoid  conifers.  In  five  of  the  fossil 
specimens  there  is  evidence  of  four  distinct  integuments,  and  of  a 
large  internal  cavity  filled  with  carbonate  of  lime  and  magnesia,  and 
probably  once  occupied  by  the  albumen  and  embryo  of  the  seed.  The 
general  form  of  the  fossil  when  perfect  is  an  elongated  ovoid,  rather 
larger  than  a  hazle-nut.  The  exterior  integument  is  very  thick  and 
cellular,  and  was  no  doubt  once  fleshy  (see  fig.  487.).  It  alone  is 
produced  beyond  the  seed,  and  forms  the  beak.  The  second  coat 
was  thinner,  but  hard,  and  marked  by  three  ridges.  This  coat, 
being  all  that  commonly  remains  in  a  fossil  state,  has  suggested  the 
name  of  Trigonocarpon.  Within  this  were  the  third  and  fourth 
coats,  both  of  which  are  very  delicate  membranes,  and  may  possibly 
have  been  two  plates  belonging  to  one  membrane. 

Grade  of  the  Carboniferous  Flora.  —  On  the  whole,  these  fruits, 
says  Dr.  Hooker,  are  referable  to  "  a  highly  developed  type,  ex- 
hibiting extensive  modifications  of  elementary  organs  for  the  pur- 
pose of  their  adaptation  to  special  functions,  and  these  modifications 
are  as  great,  and  the  adaptation  as  special,  as  any  to  be  found 
amongst  analogous  fruits  in  the  existing  vegetable  world."*  Pro- 
fessor Williamson,  in  his  paper  on  Sternbergia,  has  likewise  re- 
marked that  its  structure  was  complex,  and  that  "  at  a  period  so 
early  as  the  carboniferous  all  the  now-existing  forms  of  vegetable 
tissue  appear  to  have  been  created."  These -observations  deserve 
notice,  because  a  question  has  arisen — whether  the  Coniferce  hold  a 
high  or  a  low  position  among  flowering  plants,  —  a  point  bearing 
directly  on  the  theory  of  progressive  development.  By  some  botanists 
all  the  Gymnospermous  Dicotyledons  are  regarded  as  inferior  in 
grade  to  the  Angiosperms.  Others  hold,  with  Dr.  Hooker,  that  the 
Gymnosperms  are  not  inferior  in  rank,  having  every  typical  cha- 
racter of  the  dicotyledons  highly  developed.  Thus  Coniferae  have 
flowers,  and  are  propagated  by  seeds  which  are  developed  through 
the  mutual  action  of  the  stamens  and  ovules;  they  have  distinct 
embryos,  and  germinate  in  a  definite  manner.  The  seed-vessel  (or 
ovary)  is  not  closed,  but  this  is  also  the  case  in  some  genera  of 
angiosperms,  in  which  the  ovary  is  open  before  or  after  impreg- 
nation, so  that  this  character  cannot  be  relied  on  as  constituting  a 
fundamental  difference  in  structural  development.  The  Coniferse 
are  exogenous,  and  have  the  same  distinctions  of  pith,  wood,  bark, 
and  medullary  rays  as  have  the  angiospermous  trees.  Whether  the 
woody  fibre  with  discs  characteristic  of  Coniferae  be  a  more  or  a  less 
complex  tissue  than  the  spiral  vessels,  is  a  controverted  point.  As 
the  spiral  vessels  occur  in  the  young  shoots,  and  are  lost  in  the 

*  Proceedings  of  the  Koyal  Society,  voL  vii.  March,  1854,  p.  28. 

BB   3 


374  GRADE    OF    THE    CARBONIFEROUS   FLORA.       [Cn.  XXIT. 

mature  growth  of  some  plants,  and  as  they  appear  in  many  acrogens, 
they  do  not  seem  to  mark  'a  high  development.  In  fine,  there  is 
much  ambiguity  in  deciding  what  should  or  should  not  be  called 
high  or  low  in  vegetable  structure,  and  physiologists  entertain  very 
different  abstract  ideas  as  to  the  perfection  of  certain  organs  and 
their  relative  functional  importance,  even  where  the  function  is 
clearly  ascertained.  It  is  enough  for  the  geologist  to  know,  that 
fossil  Coniferae  abound  in  the  oldest  rocks  yielding  a  considerable 
number  of  vegetable  remains,  and  that  plants  of  this  order  lay 
claim,  if  not  to  the  highest,  at  least  to  so  high  a  place  in  the  scale  of 
vegetable  life,  as  to  preclude  us  from  characterizing  the  carbo- 
niferous flora  as  consisting  of  imperfectly  developed  plants. 

Although  our  data  are  confessedly  too  defective  to  entitle  us  to 
generalize  respecting  the  entire  vegetable  creation  of  this  era,  yet  we 
may  affirm  that  so  far  as  it  is  known  it  differed  widely  from  any 
flora  now  existing.  The  comparative  rarity  of  Monocotyledons  and 
of  Dicotyledonous  Angiosperms  seems  clear,  and  the  abundance 
of  Ferns  and  Lycopods  may  justify  Adolphe  Brongniart  in  calling 
the  primary  periods  the  age  of  Acrogens.*  ("  Le  regne  des  Aero- 
gens.")  As  to  the  Sigillariae  and  Calamites,  they  seem  to  have  been 
distinct  from  all  tribes  of  now-existing  plants.  That  the  abundance 
of  ferns  implies  a  moist  atmosphere,  is  admitted  by  all  botanists; 
but  no  safe  conclusion,  says  Hooker,  can  be  drawn  from  the  Coniferae 
alone,  as  they  are  found  in  hot  and  dry  and  in  cold  and  dry  climates, 
in  hot  and  moist  and  in  cold  and  moist  regions.  In  New  Zealand 
the  ConiferEe  attain  their  maximum  in  numbers,  constituting  ^nd 
part  of  all  the  flowering  plants  ;  whereas  in  a  wide  district  around 
the  Cape  of  Good  Hope  they  do  not  form  T^n^h  of  the  pheno- 
gamic  flora.  Besides  the  conifers,  many  species  of  ferns  flourish  in 
New  Zealand,  some  of  them  arborescent,  together  with  many  lyco- 
podiums  ;  so  that  a  forest  in  that  country  may  make  a  nearer  approach 
to  the  carboniferous  vegetation  than  any  other  now  existing  on  the 
globe. 

Angiosperms.  —  Some  of  the   grass-like  leaves  termed  Poacites, 
Fig  488  having  fine  longitudinal  striae,   are  conjectured 

to  belong  to  Monocotyledons;  but  the  determi- 
nation is  doubtful,  as  some  of  them  may  be  the 
leaves  of  Lepidodendra,  others  the  stems  of 
Ferns.  The  curious  plants  called  Antholithes 
by  Lindley  have  usually  been  considered  to  be 
flower-spikes,  having  what  seems  a  calyx  and 
linear  petals  (see  fig.  488.).  But  Dr.  Hooker 
suggests  that  these  may  be  rather  tufts  of  scarcely 
opened  buds  with  the  young  leaves  just  burst- 
ing. He  suggests  that  they  may  be  coniferous, 
although  he  cannot  connect  them  with  any  known 
s  Col-  f°ssil  conifer. 

liery,  Newcastle. 

*  For  terminology  of  classification  of  plants,  see  above,  note,  p.  267. 


CH.  XXIV.]  COAL  —  ERECT  FOSSIL   TREES.  375 

Coal,  how  formed — Erect  trees.  — I  shall  now  consider  the  manner 
in  which  the  above-mentioned  plants  are  imbedded  in  the  strata,  and 
how  they  may  have  contributed  to  produce  coal.  Professor  Goppert, 
after  examining  the  fossil  vegetables  of  the  coal-fields  of  Germany, 
has  detected,  in  beds  of  pure  coal,  remains  of  plants  of  every  family 
hitherto  known  to  occur  fossil  in  the  coal.  Many  seams,  he  remarks, 
are  rich  in  Sigillarice,  Lepidodendra,  and  Stigmarice,  the  latter  in 
such  abundance,  as  to  appear  to  form  the  bulk  of  the  coal.  In  some 
places,  almost  all  the  plants  were  calamites,  in  others  ferns.*  "  Some 
of  the  plants  of  our  coal,"  says  Dr.  Buckland,  "  grew  on  the  iden- 
tical banks  of  sand,  silt,  and  mud  which,  being  now  indurated  to 
stone  and  shale,  form  the  strata  that  accompany  the  coal;  whilst 
other  portions  of  these  plants  have  been  drifted  to  various  distances 
from  the  swamps,  savannahs,  and  forests  that  gave  them  birth,  par- 
ticularly those  that  are  dispersed  through  the  sandstones,  or  mixed 
with  fishes  in  the  shale  beds."  "  At  Balgray,  three  miles  north  of 
Glasgow,"  says  the  same  author,  "I  saw  in  the  year  1824,  as  there 
still  may  be  seen,  an  unequivocal  example  of  the  stumps  of  several 
stems  of  large  trees,  standing  close  together  in  their  native  place,  in 
a  quarry  of  sandstone  of  the  coal-formation."  f 

Between  the  years  1837  and  1840,  six  fossil  trees  were  discovered 
in  the  coal-field  of  Lancashire,  where  it  is  intersected  by  the  Bolton 
railway.  They  were  all  in  a  vertical  position,  with  respect  to  the 
plane  of  the  bed,  which  dips  about  15°  to  the  south.  The  distance 
between  the  first  and  the  last  was  more  than  100  feet,  and  the  roots 
of  all  were  imbedded  in  a  soft  argillaceous  shale.  In  the  same  plane 
with  the  roots  is  a  bed  of  coal,  eight  or  ten  inches  thick,  which  has 
been  ascertained  to  extend  across  the  railway,  or  to  the  distance  of  at 
least  ten  yards.  Just  above  the  covering  of  the  roots,  yet  beneath 
the  coal-seam,  so  large  a  quantity  of  the  Lepidostrobus  variabilis  was 
discovered  inclosed  in  nodules  of  hard  clay,  that  more  than  a  bushel 
was  collected  from  the  small  openings  around  the  base  of  the  trees 
(see  figure  of  this  genus,  p.  366.).  The  exterior  trunk  of  each  was 
marked  by  a  coating  of  friable  coal,  varying  from  one  quarter  to  three 
quarters  of  an  inch  in  thickness ;  but  it  crumbled  away  on  removing 
the  matrix.  The  dimensions  of  one  of  the  trees  is  15^  feet  in  circum- 
ference at  the  base,  7^-  feet  at  the  top,  its  height  being  1 1  feet.  All 
the  trees  have  large  spreading  roots,  solid  and  strong,  sometimes 
branching,  and  traced  to  a  distance  of  several  feet,  and  presumed  to 
extend  much  farther.  Mr.  Hawkshaw,  who  has  described  these 
fossils,  thinks  that,  although  they  were  hollow  when  submerged,  they 
may  have  consisted  originally  of  hard  wood  throughout ;  for  solid 
dicotyledonous  trees,  when  prostrated  in  tropical  forests,  as  in  Vene- 
zuela, on  the  shore  of  the  Caribbean  Sea,  were  observed  by  him  to  be 
destroyed  in  the  interior,  so  that  little  more  is  left  than  an  outer 
shell,  consisting  chiefly  of  the  bark.  This  decay,  he  says,  goes  on 

*  Quart.  GeoL  Journ.,  vol.  v.,  Mem.,        f  Anniv.  Address  to  Geol.  Soc.5 1840. 
p.  17. 

BB  4 


376  COAL  —  ERECT   FOSSIL    TREES.  [Cn.  XXIV. 

most  rapidly  in  low  and  flat  tracts,  in  which  there  is  a  deep  rich  soil 
and  excessive  moisture,  supporting  tall  forest-trees  and  large  palms, 
below  which  bamboos,  canes,  and  minor  palms  flourish  luxuriantly. 
Such  tracts,  from  their  lowness,  would  be  most  easily  submerged,  and 
their  dense  vegetation  might  then  give  rise  to  a  seam  of  coal.* 

In  a  deep  valley  near  Capel-Coelbren,  branching  from  the  higher 
part  of  the  Swansea  valley,  four  stems  of  upright  Sigillarice  were 
seen  in  1838,  piercing  through  the  coal-measures  of  S.  Wales ;  one 
of  them  was  2  feet  in  diameter,  and  one  13  feet  and  a  half  high,  and 
they  were  all  found  to  terminate  downwards  in  a  bed  of  coal.  "  They 
appear,"  says  Sir  H.  De  la  Beche,  "  to  have  constituted  a  portion  of  a 
subterranean  forest  at  the  epoch  when  the  lower  carboniferous  strata 
were  formed."  f 

In  a  colliery  near  Newcastle,  say  the  authors  of  the  Fossil  Flora, 
a  great  number  of  Sigillarice  were  placed  in  the  rock  as  if  they  had 
retained  the  position  in  which  they  grew.  Not  less  than  thirty,  some 
of  them  4  or  5  feet  in  diameter,  were  visible  within  an  area  of  50 
yards  square,  the  interior  being  sandstone,  and  the  bark  having  been 
converted  into  coal.  The  roots  of  one  individual  were  found  im- 
bedded in  shale ;  and  the  trunk,  after  maintaining  a  perpendicular 
course  and  circular  form  for  the  height  of  about  10  feet,  was  then  bent 
over  so  as  to  become  horizontal.  Here  it  was  distended  laterally,  and 
flattened  so  as  to  be  only  one  inch  thick,  the  flutings  being  compa- 
ratively distinct.!  Such  vertical  stems  are  familiar  to  our  miners, 
under  the  name  of  coal-pipes.  One  of  them,  72  feet  in  length,  was 
discovered,  in  1829,  near  Gosforth,  about  five  miles  from  Newcastle, 
in  coal-grit,  the  strata  of  which  it  penetrated.  The  exterior  of  the 
trunk  was  marked  at  intervals  with  knots,  indicating  the  points  at 
which  branches  had  shot  off.  The  wood  of  the  interior  had  been 
converted  into  carbonate  of  lime ;  and  its  structure  was  beautifully 
shown  by  cutting  transverse  slices,  so  thin  as  to  be  transparent.  (See 
p.  40.) 

These  "  coal-pipes  "  are  much  dreaded  by  our  miners,  for  almost 
every  year  in  the  Bristol,  Newcastle,  and  other  coal-fields,  they  are 
the  cause  of  fatal  accidents.  Each  cylindrical  cast  of  a  tree,  formed 
of  solid  sandstone,  and  increasing  gradually  in  size  towards  the  base, 
and  being  without  branches,  has  its  whole  weight  thrown  downwards, 
and  receives  no  support  from  the  coating  of  friable  coal  which  has 
replaced  the  bark.  As  soon,  therefore,  as  the  cohesion  of  this  ex- 
ternal layer  is  overcome,  the  heavy  column  falls  suddenly  in  a  per- 
pendicular or  oblique  direction  from  the  roof  of  the  gallery  whence 
coal  has  been  extracted,  wounding  or  killing  the  workman  who 
stands  below.  It  is  strange  to  reflect  how  many  thousands  of  these 
trees  fell  originally  in  their  native  forests  in  obedience  to  the  law  of 
gravity ;  and  how  the  few  which  continued  to  stand  erect,  obeying, 

*  Hawkshaw,  Geol.  Trans.,  Second    and  Somerset,  p.  143. 
Series,  vol.  vi.  pp.  173.  177.,  pi.  17.  J  Lindley   and  Hutton,    Foss.    Flo. 

f  Geol.  Eeport  on  Cornwall,  Devon,    part  6.  p.  150. 


CH.  XXIV.]  PAEKFIELD   COLLIERY.  377 

after  myriads  of  ages,   the  same  force,  are  cast  down  to  immolate 
their  human  victims. 

It  has  been  remarked,  that  if,  instead  of  working  in  the  dark,  the 
miner  was  accustomed  to  remove  the  upper  covering  of  rock  from 
each  seam  of  coal,  and  to  expose  to  the  day  the  soils  on  which  ancient 
forests  grew,  the  evidence  of  their  former  growth  would  be  obvious. 
Thus  in  South  Staffordshire  a  seam  of  coal  was  laid  bare  in  the  year 
1844,  in  what  is  called  an  open  work  at  Parkfield  Colliery,  near 
Wolverhampton.  In  the  space  of  about  a  quarter  of  an  acre  the 
stumps  of  no  less  than  73  trees  with  their  roots  attached  appeared, 
as  shown  in  the  annexed  plan  (fig.  489.),  some  of  them  more  than 

Fig.  489. 


Ground-plan  of  a  fossil  forest,  Parkfield  Colliery,  near  Wolverhampton, 
showing  the  position  of  73  trees  in  a  quarter  of  an  acre.* 

8  feet  in  circumference.  The  trunks,  broken  off  close  to  the  root, 
were  lying  prostrate  in  every  direction,  often  crossing  each  other. 
One  of  them  measured  15,  another  30  feet  in  length,  and  others  less. 
They  were  invariably  flattened  to  the  thickness  of  one  or  two  inches, 
and  converted  into  coal.  Their  roots  formed  part  of  a  stratum  of 
coal  10  inches  thick,  which  rested  on  a  layer  of  clay  2  inches  thick, 
below  which  was  a  second  forest,  resting  on  a  2-foot  seam  of  coal. 
Five  feet  below  this  again  was  a  third  forest  with  large  stumps  of 
Lepidodendra,  Calamites,  and  other  trees. 

In  the  account  given,  in  1821,  by  M.  Alex.  Brongniartf  of  the 
coal-mine  of  Treuil,  at  St.  Etienne,  near  Lyons,  he  states,  that  dis- 
tinct horizontal  strata  of  micaceous  sandstone  are  traversed  by  ver- 
tical trunks  of  monocotyledonous  vegetables,  resembling  bamboos 
or  large  Equiseta  (fig.  490.).  Since  the  consolidation  of  the  stone, 
there  has  been  here  and  there  a  sliding  movement,  which  has  broken 
the  continuity  of  the  stems,  throwing  the  upper  parts  of  them  on 
one  side,  so  that  they  are  often  not  continuous  with  the  lower. 

From  these  appearances  it  was  inferred  that  we  have  here  the 

*  Messrs.  Beckett  and  Ick.    Proceed.        f  Anndes  des  Mines,  1821. 
Geol.  Soc.,  vol.  iv.  p.  287. 


378 


COAL  —  ERECT   FOSSIL   TKEES. 

Fig.  490. 


[Cn.  XXIV. 


Section  showing  the  erect  position  of  fossil  trees  in  coal-sandstone  at 
St.  Etienne.    (Alex.  Brongniart.) 

monuments  of  a  submerged  forest.  I  formerly  objected  to  this  con- 
clusion, suggesting  that,  in  that  case,  all  the  roots  ought  to  have  been 
found  at  one  and  the  same  level,  and  not  scattered  irregularly 
through  the  mass.  I  also  imagined  that  the  soil  to  which  the  roots 
were  attached  should  have  been  different  from  the  sandstone  in  which 
the  trunks  are  enclosed.  Having,  however,  seen  calamites  near 
Pictou,  in  Nova  Scotia,  buried  at  various  heights  in  sandstone  and 
in  similar  erect  attitudes,  I  have  now  little  doubt  that  M.  Brong- 
niart's  view  was  correct.  These  plants  seem  to  have  grown  on  a 
sandy  soil,  liable  to  be  flooded  from  time  to  time,  and  raised  by  new 
accessions  of  sediment,  as  may  happen  in  swamps  near  the  banks  of 
a  large  river  in  its  delta.  Trees  which  delight  in  marshy  grounds 
are  not  injured  by  being  buried  several  feet  deep  at  their  base  ;  and 
other  trees  are  continually  rising  up  from  new  soils,  several  feet 
above  the  level  of  the  original  foundation  of  the  morass.  In  the 
banks  of  the  Mississippi,  when  the  water  has  fallen,  I  have  seen 
sections  of  a  similar  deposit  in  which  portions  of  the  stumps  of 
trees  with  their  roots  in  situ  appeared  at  many  different  heights.* 

When  I  visited,  in  1843,  the  quarries  of  Treuil  above-mentioned, 
the  fossil  trees  seen  in  fig.  490.  were  removed,  but  I  obtained  proofs 
of  other  forests  of  erect  trees  in  the  same  coal-field. 

Snags.  —  In  1830,  a  slanting  trunk  was  exposed  in  Craigleith 
quarry,  near  Edinburgh,  the  total  length  of  which  exceeded  60  feet. 
Its  diameter  at  the  top  was  about  7  inches,  and  near  the  base  it 
measured  5  feet  in  its  greater,  and  2  feet  in  its  lesser  width.  The  bark 
was  converted  into  a  thin  coating  of  the  purest  and  finest  coal,  form- 
ing a  striking  contrast  in  colour  with  the  white  quartzose  sandstone 

*  Principles  of  Geol.,  9th  ed,  p.  268. 


CH.  XXIV.]  COAL  —  OBLIQUE   FOSSIL   TKEES.  379 

Fig  491  in   which   it  lay.      The  annexed 

figure  represents  a  portion  of  this 
tree,  about  15  feet  long,  which 
I  saw  exposed  in  1830,  when  all 
the  strata  had  been  removed  from 
one  side.  The  beds  which  re- 
mained were  so  unaltered  and  un- 
disturbed at  the  point  of  junction, 
as  clearly  to  show  that  they  had 

Inclined  position  of  a  fossil  tree,  cutting  through    been     tranquilly     deposited     TOUnd 
horizontal  beds  of  sandstone,  Craigleith  quarry,      ,  jiij.ii  IT 

Edinburgh.    Angle  of  inclination  from  a  to  b    the  tree,  and  that  the  tree  had  not 

subsequently  pierced  through 

them,  while  they  were  yet  in  a  soft  state.  They  were  composed 
chiefly  of  siliceous  sandstone,  for  the  most  part  white ;  and  divided 
into  laminae  so  thin,  that  from  six  to  fourteen  of  them  might  be 
reckoned  in  the  thickness  of  an  inch.  Some  of  these  thin  layers 
were  dark,  and  contained  coaly  matter ;  but  the  lowest  of  the  in- 
tersected beds  were  calcareous.  The  tree  could  not  have  been 
hollow  when  Imbedded,  for  the  interior  still  preserved  the  woody 
texture  in  a  perfect  state,  the  petrifying  matter  being,  for  the  most 
part,  calcareous.*  It  is  also  clear  that  the  lapidifying  matter  was  not 
introduced  laterally  from  the  strata  through  which  the  fossil  passes, 
as  most  of  these  were  not  calcareous.  It  is  well  known  that,  in  the 
Mississippi  and  other  great  American  rivers,  where  thousands  of 
trees  float  annually  down  the  stream,  some  sink  with  their  roots 
downwards,  and  become  fixed  in  the  mud.  Thus  placed,  they  have 
been  compared  to  a  lance  in  rest ;  and  so  often  do  they  pierce  through 
the  bows  of  vessels  which  run  against  them,  that  they  render  the 
navigation  extremely  dangerous.  Mr.  Hugh  Miller  mentions  four 
other  huge  trunks  exposed  in  quarries  near  Edinburgh,  which  lay 
diagonally  across  the  strata  at  an  angle  of  about  30°,  with  their 
lower  or  heavier  portions  downwards,  the  roots  of  all,  save  one, 
rubbed  off  by  attrition.  One  of  these  was  60  and  another  70  feet 
in  length,  and  from  4  to  6  feet  in  diameter. 

The  number  of  years  for  which  the  trunks  of  trees,  when  constantly 
submerged,  can  resist  decomposition,  is  very  great;  as  we  might 
suppose  from  the  durability  of  wood,  in  artificial  piles,  permanently 
covered  by  water.  Hence  these  fossil  snags  may  not  imply  a  rapid 
accumulation  of  beds  of  sand,  although  the  channel  of  a  river  or 
part  of  a  lagoon  is  often  filled  up  in  a  very  few  years. 

Nova  Scotia.  —  One  of  the  finest  examples  in  the  world  of  a  suc- 
cession of  fossil  forests  of  the  carboniferous  period,  laid  open  to  view 
in  a  natural  section,  is  that  seen  in  the  lofty  cliffs  called  the  South 
Joggins,  bordering  the  Chignecto  Channel,  a  branch  of  the  Bay  of 
Fundy,  in  Nova  Scotia,  f 

*  See  figures  of  texture,  Witham,  vol.  ii.  p.  1 79. ;  and  Dawson,  Geol.  Journ. 
Foss.  Veget.,  pi.  3.  No.  37. 

f  See  Lyell's  Travels  in  N.  America, 


380 


COAL  —  FOSSIL    FOKESTS 


[Cn.  XXIV. 


In   the  annexed   section    (fig.  492.),   which  I 
examined  in  July,  1842,  the  beds  from  c  to  *  are 
seen  all  dipping  the  same  way,  their  average  in- 
clination being  at  an  angle  of  24°  S.S.W.     The 
vertical  height  of  the  cliffs  is  from  150  to  200 
feet ;  and  between  d  and  g,  in  which  space  I  ob- 
served seventeen  trees  in  an  upright  position,  or, 
to  speak  more  correctly,  at  right  angles  to  the 
planes  of  stratification,  I  counted  nineteen  seams 
of  coal,  varying  in  thickness  from  2  inches  to  4 
feet.     At  low  tide  a  fine  horizontal  section  of  the 
•2     same  beds  is  exposed  to  view  on  the  beach.     The 
w     thickness  of  the  beds  alluded  to,  between  d  and  g, 
§     is  about  2,500   feet,   the  erect  trees  consisting 
^     chiefly  of  large  Sigillarice,  occurring  at  ten  dis- 
1     tinct  levels,  one  above  the  other ;  but  Mr.  Logan, 
|     who  afterwards  made  a  more  detailed  survey  of 
g     the  same  line  of  cliffs,  found  erect  trees  at  seven- 
J    teen  levels,  extending  through  a  vertical  thick- 
g>    ness  of  4,515  feet  of  strata  ;  and  he  estimated  the 
£     total  thickness   of  the  carboniferous  formation, 
|     with  and  without  coal,  at    no  less  than  14,570 
«     feet,  every  where  devoid  of  marine  organic  re- 
£     mains.*      The  usual  height  of  the  buried   trees 
sg     seen  by  me  was  from  6  to  8  feet ;  but  one  trunk 
£.    was  about  25  feet  high  and  4  feet  in  diameter, 
*j     with  a  considerable  bulge  at  the  base.      In  no 
g     instance  could  I  detect  any  trunk  intersecting  a 
"$     layer  of   coal,   however  thin ;    and  most  of  the 
trees  terminated   downwards   in    seams  of  coal. 
Some  few  only  were  based   in   clay  and  shale ; 
none  of  them,  except   calamites,    in    sandstone. 
The  erect  trees,  therefore,  appeared  in  general  to 
have  grown  on  beds  of  coal.     In  the  underclays 
Stigmaria  abounds. 

In  1852  Mr.  Dawson  and  the  author  made  a 
detailed  examination  of  one  portion  of  the  strata, 
1400  feet  thick,  where  the  coal-seams  are  most 
frequent,  and  found  evidence  of  root-bearing  soils 
at  sixty-eight  different  levels.  Like  the  seams 
of  coal  which  often  cover  them,  these  root-beds 
or  old  soils  are  at  present  the  most  destructible  masses  in  the  whole 
cliff,  the  sandstones  and  laminated  shales  being  harder  and  more 
capable  of  resisting  the  action  of  the  waves  and  the  weather.  Origi- 
nally the  reverse  was  doubtless  true,  for  in  the  existing  delta  of 
the  Mississippi  those  clays  in  which  the  innumerable  roots  of  the 
deciduous  cypress  and  other  swamp  trees  ramify  in  all  directions  are 
seen  to  withstand  far  more  effectually  the  undermining  power  of  the 

*  Quart.  Geol.  Journ.,  vol.  ii.  p.  177. 


CH.  XXIV.J 


IN    NOVA   SCOTIA. 


381 


river,  or  of  the  sea  at  the  base  of  the  delta,  than  do  beds  of  loose 
sand  or  layers  of  mud  not  supporting  trees. 

This  fact  may  explain  why  seams  of  coal  have  so  often  escaped 
denudation,  and  remain  continuous  over  wide  areas,  since  the  tough 
roots,  now  turned  to  coal,  which  once  traversed  them,  would  enable 
them  to  resist  a  current  of  water,  whilst  other  members  of  the  coal- 
formation,  in  their  original  and  unconsolidated  state  of  sand  and 
mud,  would  be  readily  removed. 

In  regard  to  the  plants,  they  belonged  to  the  same  genera,  and 
most  of  them  to  the  same  species,  as  those  met  with  in  the  distant 
coal-fields  of  Europe.  In  the  sandstone,  which  filled  their  interiors, 
I  frequently  observed  fern  leaves,  and  sometimes  fragments  of  Stiff - 
maria,  which  had  evidently  entered  together  with  sediment  after 
the  trunk  had  decayed  and  become  hollow,  and  while  it  was  still 
standing  under  water.  Thus  the  tree,  a  b,  fig.  493.,  the  same  which 
is  represented  at  «,  fig.  494.,  or  in  the  bed  e  in  the  larger  section, 
fig.  492.,  is  a  hollow  trunk  5  feet  8  inches  in  length,  traversing 
various  strata,  and  cut  off  at  the  top  by  a  layer  of  clay  2  feet  thick, 

Fig.  493. 


Fossil  tree  at  right  angles  to  the  planes  of  stratification. 
Coal-measures,  Nova  Scotia. 

Fig.  494. 


Erect  fossil  trees.    Coal-measures,  Nova  Scotia. 


on  which  rests  a  seam  of  coal  (£,  fig.  494.)  1  foot  thick.  On  this 
coal  again  stood  two  large  trees  (c  and  d),  while  at  a  greater  height 
the  trees  f  and  g  rest  upon  a  thin  seam  of  coal  (e),  and  above 
them  is  an  underclay,  supporting  the  4-foot  coal. 


382  COAL  —  FOSSIL   FORESTS  [CH.  XXIV. 

If  we  now  return  to  the  tree  first  mentioned  (fig.  493.),  we  find 
the  diameter  (a  b)  14  inches  at  the  top  and  16  inches  at  the  bottom, 
the  length  of  the  trunk  5  feet  8  inches.  The  strata  in  the  interior 
consisted  of  a  series  entirely  different  from  those  on  the  outside. 
The  lowest  of  the  three  outer  beds  which  it  traversed  consisted  of 
purplish  and  blue  shale  (c,  fig.  493.),  2  feet  thick,  above  which  was 
sandstone  (d)  1  foot  thick,  and,  above  this,  clay  (e)  2  feet  8  inches. 
But,  in  the  interior,  were  nine  distinct  layers  of  different  composi- 
tion :  at  the  bottom,  first,  shale  4  inches,  then  sandstone  1  foot,  then 
shale  4  inches,  then  sandstone  4  inches,  then  shale  1 1  inches,  then 
clay  (/)  with  nodules  of  ironstone  2  inches,  then  pure  clay  2  feet, 
then  sandstone  3  inches,  and,  lastly,  clay  4  inches.  Owing  to  the 
outward  slope  of  the  face  of  the  cliff,  the  section  (fig.  493.)  was  not 
exactly  perpendicular  to  the  axis  of  the  tree ;  and  hence,  probably, 
the  apparent  sudden  termination  at  the  base  without  a  stump  and  roots. 
In  this  example  the  layers  of  matter  in  the  inside  of  the  tree  are 
more  numerous  than  those  without ;  but  it  is  more  common  in  the 
coal-measures  of  all  countries  to  find  a  cylinder  of  pure  sandstone,  — 
the  cast  of  the  interior  of  a  tree,  — intersecting  a  great  many 
alternating  beds  of  shale  and  sandstone,  which  originally  enveloped 
the  trunk  as  it  stood  erect  in  the  water.  Such  a  want  of  corres- 
pondence in  the  materials  outside  and  inside,  is  just  what  we  might 
expect  if  we  reflect  on  the  difference  of  time  at  which  the  deposition 
of  sediment  will  take  place  in  the  two  cases  ;  the  imbedding  of  the 
tree  having  gone  on  for  many  years  before  its  decay  had  made  much 
progress. 

In  many  places  distinct  proof  is  seen  that  the  enveloping  strata 
took  years  to  accumulate,  for  some  of  the  sandstones  surrounding 
erect  sigillarian  trunks  support  at  different  levels  roots  and  stems 
of  Calamites ;  the  Calamites  having  begun  to  grow  after  the  older 
Sigillarice  had  been  partially  buried. 

The  general  absence  of  structure  in  the  interior  of  the  large  fossil 
trees  of  the  Coal  implies  the  very  durable  nature  of  their  bark,  as 
compared  with  their  woody  portion.  The  same  difference  of  dura- 
bility of  bark  and  wood  exists  in  modern  trees,  and  was  first  pointed 
out  to  me  by  Mr.  Dawson,  in  the  forests  of  Nova  Scotia,  where  the 
Canoe  Birch  (Betula  papyracea)  has  such  tough  bark  that  it  may 
sometimes  be  seen  in  the  swamps  looking  externally  sound  and  fresh, 
although  consisting  simply  of  a  hollow  cylinder  with  all  the  wood 
decayed  and  gone.  In  such  cases  the  submerged  portion  is  some- 
times found  filled  with  mud. 

One  of  the  erect  fossil  trees  of  the  South  Joggins  has  been  shown 
by  Mr.  Dawson  to  have  Araucarian  structure,  so  that  some  Coniferce 
of  the  Coal  Period  grew  in  the  same  swamps  as  Sigillarice,  just  as 
now  the  deciduous  Cypress  ( Taxodium  distichum)  abounds  in  the 
marshes  of  Louisiana  even  to  the  edge  of  the  sea. 

When  the  carboniferous  forests  sank  below  high-water  mark  a 
species  of  Spirorbis  or  Serpula  (fig.  498.)  attached  itself  to  the  out- 
side of  the  stumps  and  stems  of  the  erect  trees,  adhering  occasionally 


CH.  XXIV.]  OF   NOVA   SCOTIA.  383 

even  to  the  interior  of  the  bark, — another  proof  that  the  process  of 
envelopment  was  very  gradual.  These  hollow  upright  trees,  covered 
with  innumerable  marine  annelids,  reminded  me  of  a  "  cane-brake," 
as  it  is  commonly  called,  consisting  of  tall  reeds  of  Arundinaria 
macrosperma,  which  I  saw,  in  1846,  at  the  Balize,  or  extremity  of  the 
delta  of  the  Mississippi.  Although  these  reeds  are  freshwater  plants, 
they  were  covered  with  barnacles,  having  been  killed  by  an  incursion 
of  salt  water  over  an  extent  of  many  acres,  where  the  sea  had  for 
a  season  usurped  a  space  previously  gained  from  it  by  the  river. 
Yet  the  dead  reeds,  in  spite  of  this  change,  remained  standing  in  the 
soft  mud,  showing  how  easily  the  Sigillarice,  hollow  as  they  were 
but  supported  by  strong  roots,  may  have  resisted  an  incursion  of 
the  sea. 

The  high  tides  of  the  Bay  of  Fundy,  rising  more  than  60  feet,  are 
so  destructive  as  to  undermine  and  sweep  away  continually  the 
whole  face  of  the  cliffs,  and  thus  a  new  crop  of  erect  fossil  trees  is 
brought  into  view  every  three  or  four  years.  They  are  known  to 
extend  over  a  space  between  two  or  three  miles  from  north  to  south, 
and  more  than  twice  that  distance  from  east  to  west,  being  seen  in 
the  banks  of  streams  intersecting  the  coal-field. 

In  Cape  Breton,  Mr.  Richard  Brown  has  observed  in  the  Sydney 
coal-field  a  total  thickness  of  coal-measures,  without  including  the 
underlying  millstone -grit,  of  1843  feet,  dipping  at  an  angle  of  8°. 
He  has  published  minute  details  of  the  whole  series,  showing  at  how 
many  different  levels  erect  trees  occur,  consisting  of  Sigillaria,  Le- 
pidodendron,  Calamites,  and  other  genera.  In  one  place  eight  erect 
trunks,  with  roots  and  rootlets  attached  to  them,  were  seen  at  the 
same  level,  within  a  horizontal  space  80  feet  in  length.  Beds  of 
coal  of  various  thickness  are  interstratified.  Taking  into  account 
forty-one  clays  filled  with  roots  of  Stigmaria  in  their  natural  position, 
and  eighteen  layers  of  upright  trees  at  other  levels,  there  is,  on  the 
whole,  clear  evidence  of  at  least  fifty-nine  fossil  forests,  ranged  one 
above  the  other,  in  this  coal-field,  in  the  above-mentioned  thickness 
of  strata.*  •  , 

The  fossil  shells  of  Cape  Breton  and  those  of  the  Nova  Scotia 
section  (p.  380.),  consisting  of  Cypris,  Unio  (?),  Modiola,  and  an 
annelid  probably  of  the  genus  Spirorbis  (see  jig.  498.),  seem  to 
indicate  brackish  water  ;  but  we  ought  never  to  be  surprised  if,  in 
pursuing  the  same  stratum,  we  should  come  either  to  a  freshwater 
or  a  purely  marine  deposit ;  for  this  will  depend  upon  our  taking  a 
direction  higher  up  or  lower  down  the  ancient  river  or  delta  deposit. 

In  the  strata  above  described,  the  association  of  clays  supporting 
upright  trees,  with  other  beds  containing  ma'rine  and  brackish-water 
shells,  implies  such  a  repeated  change  in  the  same  area,  from  land  to 
sea  and  from  sea  to  land,  that  here,  if  anywhere,  we  should  expect  to 
meet  with  evidence  of  the  fall  of  rain  on  ancient  sea-beaches.  Ac- 
cordingly rain-prints  were  seen  by  me  and  Mr.  Dawson  at  various 

*  Geol.  Quart.  Journ.,  vol.  ii.  p.  393.;  and  vol.  vi.  p.  115. 


384 


COAL  —  RAIN-PRINTS. 


[CH.  XXIV. 


levels,  but  the  most  perfect  'hitherto  observed  were  discovered  by 
Mr.  Brown  near  Sydney  in  Cape  Breton.  They  consist  of  very  deli- 
cate impressions  of  rain-drops  on  greenish  slates,  with  several  worm- 
tracks  («,  b,  fig.  495.),  such  as  usually  accompany  rain-marks  on 
the  recent  mud  of  the  Bay  of  Fundy,  and  other  modern  beaches. 


,  Fig.  495. 


Fig.  496. 


Fig.  495.  Carboniferous  rain-prints  with  worm-tracks  («,  6)  on  green  shale,  from  Cape 
Breton,  Nova  Scotia.    Natural  size. 

Fig.  496.  Casts  of  rain-prints  on  a  portion  of  the  same  slab,  tig.  495.,  seen  on  the  under 
side  of  an  incumbent  layer  of  arenaceous  shale.    Natural  size, 
The  arrow  represents  the  supposed  direction  of  the  shower. 

The  casts  of  rain-prints,  in  figs.  496.  and  497.,  project  from  the 
under  side  of  two  layers,  occurring  at  different  levels,  the  one  a 
sandy  shale,  resting  on  the  green  shale  (fig.  495.),  the  other  a  sand- 
Fig.  497. 


Fig.  497.  Casts  of  carboniferous  rain-prints  and  shrinkage-cracks  (a)  on  the  under 
side  of  a  layer  of  sandstone,  Cape  Breton,  Nova  Scotia.    Nat ural  size. 

stone  presenting  a  simflar  warty  or  blistered  surface,  on  which  are 
also  observable  some  small  ridges  as  at  a,  which  stand  out  in  relief, 
and  afford  evidence  of  cracks  formed  by  the  shrinkage  of  subjacent 
clay,  on  which  rain  had  fallen.  Many  of  the  associated  sandstones 
are  ripple-marked. 

The  great  humidity  of  the  climate  of  the  coal-period  had  been 
previously  inferred  from  the  nature  of  its  vegetation  and  the  con- 


CH.  XXIV.]  PURITY   OF   THE   COAL.  385 

tinuity  of  its  forests  for  hundreds  of  miles  ;  but  it  is  satisfactory  to 
have  at  length  obtained  such  positive  proofs  of  showers  of  rain,  the 
drops  of  which  resembled  in  their  average  size  those  which  now  fall 
from  the  clouds.  From  such  data  we  may  presume  that  the  at- 
mosphere of  the  carboniferous  period  corresponded  in  density  with 
that  now  investing  the  globe,  and  that  different  currents  of  air 
varied  then  as  now  in  temperature,  so  as  to  give  rise,  by  their 
mixture,  to  the  condensation  of  aqueous  vapour. 

The  more  closely  the  strata  productive  of  coal  have  been  studied 
the  greater  has  become  the  force  of  the  evidence  in  favour  of  their 
having  originated  in  the  manner  of  modern  deltas.  They  display 
a  vast  thickness  of  stratified  mud  and  fine  sand  without  pebbles,  and 
in  them  are  seen  countless  stems,  leaves,  and  roots  of  terrestrial 
plants,  free  for  the  most  part  from  all  intermixture  of  marine 
remains,  —  circumstances  which  imply  the  persistency  in  the  same 
region  of  a  vast  body  of  fresh  water.  This  water  was  also  charged, 
like  that  of  a  great  river,  with  an  inexhaustible  supply  of  sediment, 
which  seems  to  have  been  transported  over  alluvial  plains  so  far 
from  the  higher  grounds  that  all  coarser  particles  and  gravel  were 
left  behind.  Such  phenomena  imply  the  drainage  and  denudation 
of  a  continent  or  large  island,  having  within  it  one  or  more  ranges 
of  mountains.  The  partial  intercalation  of  brackish-water  beds  at 
certain  points  is  equally  consistent  with  the  theory  of  a  delta,  the 
lower  parts  of  which  are  always  exposed  to  be  overflowed  by  the  sea 
even  where  no  oscillations  of  level  are  experienced. 

The  purity  of  the  coal  itself,  or  the  absence  in  it  of  earthy  par- 
ticles and  sand,  throughout  areas  of  vast  extent,  is  a  fact  which 
appears  very  difficult  to  explain  when  we  attribute  each  coal-seam 
to  a  vegetation  growing  in  swamps.  It  has  been  asked  how,  during 
river  inundations,  capable  of  sweeping  away  the  leaves  of  ferns  and 
the  stems  and  roots  of  Sigillarice  and  other  trees,  could  the  waters 
fail  to  transport  some  fine  mud  into  the  swamps  ?  One  generation 
after  another  of  tall  trees  grew  with  their  roots  in  mud,  and  their 
leaves  and  prostrate  trunks  formed  layers  of  vegetable  matter,  which 
was  afterwards  covered  with  mud  since  turned  to  shale.  Yet  the 
coal  itself  or  altered  vegetable  matter  remained  all  the  while 
unsoiled  by  earthy  particles.  This  enigma,  however  perplexing  at 
first  sight,  may,  I  think,  be  solved,  by  attending  to  what  is  now 
taking  place  in  deltas.  The  dense  growth  of  reeds  and  herbage 
which  encompasses  the  margins  of  forest-covered  swamps  in  the 
valley  and  delta  of  the  Mississippi  is  such  that  the  fluviatile 
waters,  in  passing  through  them,  are  filtered  and  made  to  clear 
themselves  entirely  before  they  reach  the  areas  in  which  vegetable 
matter  may  accumulate  for  centuries,  forming  coal  if  the  climate 
be  favourable.  There  is  no  possibility  of  the  least  intermixture 
of  earthy  matter  in  such  cases.  Thus  in  the  large  submerged 
tract  called  the  "  Sunk  Country,"  near  New  Madrid,  forming  part  of 
the  western  side  of  the  valley  of  the  Mississippi,  erect  trees  have 
been  standing  ever  since  the  year  1811-12,  killed  by  the  great 

C  C 


386  LONG   PERIODS   OF   ACCUMULATION.        [Cn.  XXIV. 

earthquake  of  that  date ;  lacustrine  and  swamp  plants  have  been 
growing  there  in  the  shallows,  and  several  rivers  have  annually 
inundated  the  whole  space,  and  yet  have  been  unable  to  'carry  in 
any  sediment  within  the  outer  boundaries  of  the  morass,  so  dense  is 
the  marginal  belt  of  reeds  and  brushwood.  It  may  be  affirmed  that 
generally  in  the  "cypress  swamps"  of  the  Mississippi  no  sediment 
mingles  with  the  vegetable  matter  accumulated  there  from  the  decay 
of  trees  and  semi-aquatic  plants.  As  a  singular  proof  of  this  fact,  I 
may  mention  that  whenever  any  part  of  a  swamp  in  Louisiana  is  dried 
up,  during  an  unusually  hot  season,  and  the  wood  set  on  fire,  pits 
are  burnt  into  the  ground  many  feet  deep,  or  as  far  down  as  the  fire 
can  descend,  without  meeting  with  water,  and  it  is  then  found  that 
scarcely  any  residuum  or  earthy  matter  is  left.*  At  the  bottom  of  all 
these  "  cypress  swamps"  a  bed  of  clay  is  found,  with  roots  of  the 
tall  cypress  (Taxodium  distickum),  just  as  the  underclays  of  the  coal 
are  filled  with  Stigmaria. 

It  has  been  already  stated,  that  the  carboniferous  strata  at  the 
South  Joggins,  in  Nova  Scotia,  are  nearly  three  miles  thick,  and 
the  coal-measures  are  ascertained  to  be  of  vast  thickness  near  Pictou, 
more  than  100  miles  to  the  eastward.  If,  therefore,  we  speculate  on 
the  probable  volume  of  solid  matter,  contained  in  the  Nova  Scotia 
coal-fields,  there  appears  little  danger  of  erring  on  the  side  of  excess 
if  we  take  the  average  thickness  of  the  beds  at  7,500  feet,  or  about 
half  that  ascertained  to  exist  in  one  carefully  measured  section.  As 
to  the  area  of  the  coal-field,  it  includes  a  large  part  of  New  Bruns- 
wick to  the  west,  and  extends  north  to  Prince  Edward's  Island,  and 
probably  to  the  Magdalen  Isles.  When  we  add  the  Cape  Breton 
beds,  and  the  connecting  strata,  which  must  have  been  denuded  or 
are  still  concealed  beneath  the  waters  of  the  Gulf  of  St.  Lawrence, 
we  obtain  an  area  comprising  about  36,000  square  miles.  This, 
with  the  thickness  of  7,500  feet  before  assumed,  will  give  51,000 
cubic  miles  of  solid  matter  as  the  volume  of  the  carboniferous  rocks. 

The  Mississippi  would  take  more  than  two  million  of  years  to 
convey  to  the  Gulf  of  Mexico  an  equal  quantity  of  solid  matter  in 
the  shape  of  sediment,  assuming  the  average  discharge  of  water,  in 
that  great  river  to  be,  as  calculated  by  Mr.  Forshey,  450,000  cubic 
feet  per  second,  throughout  the  year,  and  the  total  quantity  of  mud  to 
be,  as  estimated  by  Mr.  Eiddell,  3,702,758,400  cubic  feet  in  the  year.f 

The  Ganges,  according  to  the  data  supplied  to  me  by  Mr.  Everest 
and  Captain  Strachey,  conveys  so  much  larger  a  volume  of  solid 
matter  annually  to  the  Bay  of  Bengal,  that  it  might  accomplish  a 
similar  task  in  375,000  years,  or  in  less  than  a  fifth  of  the  time 
which  the  Mississippi  would  require.  J 

As  the  lowest  of  the  carboniferous  strata  of  Nova  Scotia,  like  the 
middle  and  uppermost,  consist  of  shallow-water  beds,  the  whole 
vertical  subsidence  of  three  miles,  at  the  South  Joggins,  must  have 

*  LyelTs  Second  Visit  to  the  U.  S.,         f  Principles  of  Geology,  9th  ed.  1853, 
vol.  ii.  p.  245.;  and  American  Journ.  of    p.  273. 
Science,  2d  series,  vol.  v.  p.  17.  f  Ibid.  1853,  p.  283. 


CH.  XXIV.]      BRACKISH- WATER  AND  MARINE  STRATA.  387 

'taken  place  gradually.  If  then  this  depression  was  brought  about  in 
the  course  of  375,000  years,  it  did  not  exceed  the  rate  of  four  feet  in 
a  century,  resembling  that  now  experienced  in  certain  countries, 
where,  whether  the  movement  be  upward  or  downward,  it  is  quite 
insensible  to  the  inhabitants,  and  only  known  by  scientific  inquiry. 
If,  on  the  other  hand,  it  was  brought  about  in  two  millions  of  years 
according  to  the  other  standard  before  alluded  to,  the  rate  would  be 
only  six  inches  in  a  century.  But  the  same  movement  taking  place 
in  an  upward  direction  would  be  sufficient  to  uplift  a  portion  of  the 
earth's  crust  to  the  height  of  Mont  Blanc,  or  to  a  vertical  elevation 
of  three  miles  above  the  level  of  the  sea. 

The  delta  of  the  Ganges  presents  in  one  respect  a  striking  parallel 
to  the  Nova  Scotia  coal-field,  since  at  Calcutta  at  the  depth  of  eight 
or  ten  feet  from  the  surface  the  buried  stools  of  trees  with  their  roots 
attached  have  been  found  in  digging  tanks,  indicating  an  ancient  soil 
now  underground ;  and,  in  boring  on  the  same  site  for  an  Artesian 
well  to  the  depth  of  481  feet,  other  signs  of  ancient  forest-covered 
lands  and  peaty  soils  have  been  observed  at  several  depths,  even  as 
far  down  as  300  feet  and  more  below  the  level  of  the  sea.  As  the 
strata  pierced  through  contained  freshwater  remains  of  recent  species 
of  plants  and  animals,  they  imply  a  subsidence  which  has  been  going 
on  contemporaneously  with  the  accumulation  of  fluviatile  mud. 

In  the  English  coal-fields  the  same  association  of  fresh,  or  rather 
brackish-water  strata,  with  marine,  in  close  connection  with  beds  of 
coal  of  terrestrial  origin,  has  been  frequently  recognised.  Thus, 
for  example,  a  deposit  near  Shrewsbury,  probably  formed  in  brackish 
water,  has  been  described  by  Sir  R.  Murchison  as  the  youngest 
member  of  the  carboniferous  series  of  that  jdistrict,  at  the  point 
where  the  coal-measures  are  in  contact  with  the  Permian  or  "  Lower 
New  Red."  It  consists  of  shales  and  sandstones  about  150  feet 
thick,  with  coal  and  traces  of  plants ;  including  a  bed  of  limestone, 
varying  from  2  to  9  feet  in  thickness,  which  is  cellular,  and  resem- 
bles some  lacustrine  limestones  of  France  and  Germany.  It  has  been 
traced  for  30  miles  in  a  straight  line,  and  can  be  recognised  at  still 
more  distant  points.  The  characteristic  fossils  are  a  small  bivalve, 
having  the  form  of  a  Cyclas  or  Cyrena,  also  a  small  entomostracan 
which  may  be  a  Cypris  or,  if  marine,  a  Cy there  (fig.  499.),  and  the 
microscopic  shell  of  an  annelid  of  an  extinct  genus  called  Micro- 
conchus  (  fig.  498.),  allied  to  Serpula  or  Spirorbis. 

Fig.  498.  Fig.  499. 


a.  Microconchus  (Spirorbis)  ^ktiuJP           Cypris  finflata  (or  Cy  there?), 
carbonarius.     Nat.  size,  Nat.  size,  aud  magnified, 
and  magnified.  g                   Murchison.* 

b.  var.  of  same. 


*  Silurian  System,  p.  84. 
cc  2 


388 


CRUSTACEANS   OF    THE   COAL. 


[Cn.  XXIV. 


Fig.  500. 


Limulus  rotundatus,  Prestwich. 
Coal,  Coalbrook  Dale. 


In  the  lower  coal-measures  of  Coalbrook  Dale,  the  strata,  accord- 
ing to  Mr.  Prestwich,  often  change  completely  within  very  short  dis- 
tances, beds  of  sandstone  passing  horizontally  into  clay,  and  clay 
into  sandstone.  The  coal-seams  often  wedge  out  or  disappear  ;  and 
sections,  at  places  nearly  contiguous,  present  marked  lithological  dis- 
tinctions. In  this  single  field,  in  which  the  strata  are  from  700  to 
800  feet  thick,  between  forty  and  fifty  species  of  terrestrial  plants 
have  been  discovered,  besides  several  fishes  of  the  genera  Megalich- 
thys,  Holopty chiiis,  and  others.  Crustacea 
also  are  met  with,  of  the  genus  Limulus 
(see  fig.  500.),  resembling  in  all  essential 
characters  the  Limuli  of  the  Oolitic 
period,  and  the  king-crab  of  the  modern 
seas.  They  were  smaller,  however,  than 
the  living  form,  and  had  the  abdomen 
deeply  grooved  across,  and  serrated  at  its 
edges.  In  this  specimen,  the  tail  is 
wanting;  but  in  another,  of  a  second 
species,  from  Coalbrook  Dale,  the  tail  is 
seen  to  agree  with  that  of  the  living  Limulus. 

The  perfect  carapace  of  a  long-tailed  or  decapod  crustacean  has 
also  been  found  in  the  ironstone  of  these  strata  by  Mr.  Ick  (see  fig. 
501.).  It  is  referred  by  Mr.  Salter  to  Glyphea,  a  genus  also  occur- 
ring in  the  Lias  and  Oolite.  There  are  also 
upwards  of  forty  species  of  mollusca,  among 
which  are  two  or  three  referred  to  the  fresh- 
water genus  Unio,  and  others  of  marine 
forms,  such  as  Nautilus,  Orthoceras,  Spirifer, 
and  Productus.  Mr.  Prestwich  suggests  that 
the  intermixture  of  beds  containing  fresh- 
water shells  with  others  full  of  marine  remains, 
and  the  alternation  of  coarse  sandstone  and 
conglomerate  with  beds  of  fine  clay  or  shale 
containing  the  remains  of  plants,  may  be  ex- 
'plained  by  supposing  the  deposit  of  Coalbrook 
Coal"  Dale  to  have  originated  in  a  bay  of  the  sea 
or  estuary  into  which  flowed  a  considerable 
river  subject  to  occasional  freshes.* 

One  or  more  species  of  scorpions,  two  beetles  of  the  family  Curcu- 
lionidce,  and  a  neuropterous  Insect  resembling  the  genus  Corydalis, 
and  another  related  to  the  Phasmida,  have  been  found  at  Coalbrook 
Dale.  From  the  coal  of  Wetting  in  Westphalia  several  specimens 
of  the  cockroach  or  Blatta  family,  and  the  wing  of  a  cricket 
(Acridites),  have  been  described  by  Germar.f 

More  recently  (1854)  Mr.  Fr.  Goldenberg  has  published  de- 
scriptions of  no  less  than  twelve  species  of  insects  from  the  nodular 


Fig.  501. 


Giyphea  f  dubia,  Saiter. 


*  Prestwich,  GeoL  Trans.,  2d 
rol.  v.  p.  440. 


f  See  Miinster's  Beitr.  vol.  v.  pi.  13. 
1842. 


CLAY-IRON-STONE. 


389 


CH.  XXIV.] 

clay-iron-stone  of  Saarbriick  near  Treves.*  They  are  associated 
with  the  leaves  and  branches  of  fossil  ferns.  Among  them  are 
several  Blattince,  three  species  of  Neuroptera,  one  beetle  of  the 
Scarabceus  family,  a  grasshopper  or  locust,  Gryllacris  (see  fig.  502.), 


Fig.  502. 


Wing  of  a  Grasshopper. 

Gryllacris  lilhanthraca,  Goldenberg. 

Coal,  Saarbriick  near  Treves. 

and  several  white  ants  or  Termites.  These  newly  added  species 
probably  outnumber  all  we  knew  before  of  the  fossil  insects  of  the 
coal. 

In  the  Edinburgh  coal-field,  at  Burdiehouse,  fossil  fishes,  mollusks, 
and  cyprides  (?),  very  similar  to  those  in  Shropshire  and  Stafford- 
shire, have  been  found  by  Dr.  Hibbert.  In  the  coal-field  also  of 
Yorkshire  there  are  freshwater  strata,  some  of  which  contain  shells 
referred  to  the  genus  Unio ;  but  in  the  midst  of  the  series  there  is  one 
thin  but  very  widely  spread  stratum,  abounding  in  fishes  and  marine 
shells,  such  as  Goniatites  Listeri  (fig.  503.),  Orthoceras,  and  Avicula 
papyracea,  Goldf.  (fig.  504.) 


Fig.  503. 


Fig.  504. 


Goniatites  Listeri,  Martin,  sp. 


Avicula  papyracea,  Goldf. 
(Pecten  papyraceus,  Sow.) 


No  similarly  intercalated  layer  of  marine  shells  has  been  noticed 
in  the  neighbouring  coal-field  of  Newcastle,  where,  as  in  South 
Wales  and  Somersetshire,  the  marine  deposits  are  entirely  below 
those  containing  terrestrial  and  freshwater  remains.^ 

Clay-iron-stone. — Bands  and  nodules  of  clay-iron-stone  are  common 
in  coal-measures,  and  are  formed,  says  Sir  H.  De  la  Beche,  of  car- 
bonate of  iron  mingled  mechanically  with  earthy  matter,  like  that 
constituting  the  shales.  Mr.  Hunt,  of  the  Museum  of  Practical 

*  Palaeont.  Dunker  and  V.  Meyer,  f  Phillips;  art.  "Geology,"  Encyc. 
vol.  iv.  p.  17.  Metrop.  p.  592. 

C  C  3 


390  CLAY-IRON-STONE.  [Cn.  XXIV. 

Geology,  instituted  a  series  of  experiments  to  illustrate  the  produc- 
tion of  this  substance,  and  found  that  decomposing  vegetable  matter, 
such  as  would  be  distributed  through  all  coal-strata,  prevented  the 
farther  oxidation  of  the  proto-salts  of  iron,  and  converted  the  per- 
oxide into  protoxide  by  taking  a  portion  of  its  oxygen  to  form  car- 
bonic acid.  Such  carbonic  acid,  meeting  with  the  protoxide  of  iron 
in  solution,  would  unite  with  it  and  form  a  carbonate  of  iron  ;  and 
this  mingling  with  fine  mud,  when  the  excess  of  carbonic  acid  was 
removed,  might  form  beds  or  nodules  of  argillaceous  iron-stone.  * 

*  Memoirs  of  Geol.  Survey,  pp.  51.  255,  &c. 


COAL-FIELDS   OF   UNITED   STATES.  391 


CHAPTER  XXV. 

CARBONIFEROUS  GROUP — continued. 

Coal-fields  of  the  United  States — Section  of  the  country  between  the  Atlantic  and 
Mississippi — Position  of  land  in  the  carboniferous  period  eastward  of  the  Al- 
leghanies — Mechanically  formed  rocks  thinning  out  westward,  and  limestones 
thickening — Uniting  of  many  coal-seams  into  one  thick  bed  —  Horizontal  coal 
at  Brownsville,  Pennsylvania — Vast  extent  and  continuity  of  single  seams  of 
coal — Ancient  river-channel  in  Forest  of  Dean  coal-field — Climate  of  car- 
boniferous period — Insects  in  coal — Rarity  of  air-breathing  animals  —  Great 
number  of  fossil  fish  —  First  discovery  of  the  skeletons  of  fossil  reptiles  —  Foot- 
prints of  reptilians — First  land-shell  found  —  Rarity  of  air-breathers,  whether 
vertebrate  or  invertebrate,  in  Coal-measures — Mountain  limestone — Its  corals 
and  marine  shells. 

IT  was  stated  in  the  last  chapter  that  a  great  uniformity  prevails  in 
the  fossil  plants  of  the  coal-measures  of  Europe  and  North  America ; 
and  I  may  add  that  four-fifths  of  those  collected  in  Nova  Scotia  have 
been  identified  with  European  species.  Hence  the  former  existence, 
at  the  remote  period  under  consideration  (the  carboniferous),  of  a 
continent  or  chain  of  islands  where  the  Atlantic  now  rolls  its  waves 
seems  a  fair  inference.  Nor  are  there  wanting  other  and  indepen- 
dent proofs  of  such  an  ancient  land  situated  to  the  eastward  of  the 
present  Atlantic  coast  of  North  America ;  for  the  geologist  deduces 
the  same  conclusion  from  the  mineral  composition  of  the  carbonifer- 
ous and  some  older  groups  of  rocks  as  they  are  developed  on  the 
eastern  flanks  of  the  Alleghanies,  contrasted  with  their  character  in 
the  low  country  to  the  westward  of  those  mountains. 

The  annexed  diagram  (fig.  505.)  will  assist  the  reader  in  under- 
standing the  phenomena  now  alluded  to,  although  I  must  guard  him 
against  supposing  that  it  is  a  true  section.  A  great  number  of 
details  have  of  necessity  been  omitted,  and  the  scale  of  heights  and 
horizontal  distances  are  unavoidably  falsified. 

Starting  from  the  shores  of  the  Atlantic,  on  the  eastern  side  of 
the  Continent,  we  first  come  to  a  low  region  (A  B),  which  was  called 
the  alluvial  plain  by  the  first  geographers.  It  is  occupied  by  tertiary 
and  cretaceous  strata,  before  described  (pp.  181.  232.  and  255.), 
which  are  nearly  horizontal.  The  next  belt,  from  B  to  c,  consists  of 
granitic  rocks  (hypogene),  chiefly  gneiss  and  mica-schist,  covered 
occasionally  with  unconformable  red  sandstone,  No.  4.  (New  Red  or 
Trias  ?),  remarkable  for  its  footprints  (see  p.  348.).  Sometimes,  also, 
this  sandstone  rests  on  the  edges  of  the  disturbed  paleozoic  rocks  (as 
seen  in  the  section).  The  region  (B  c),  sometimes  called  the  "  Atlan- 
tic Slope,"  corresponds  nearly  in  average  width  with  the  low  and  flat 
plain  (A  B),  and  is  characterized  by  hills  of  moderate  height,  con- 
trasting strongly,  in  their  rounded  shape  and  altitude,  with  the  long, 

cc  4 


392   GEOLOGICAL  STRUCTURE  OF  UNITED  STATES.   [Cn.  XXV. 


II 


I     , 


5;2  =  S2 


s 

**• 


.2.2°»-o 

Ss-g  sill  = 


cC 


*«  2  I    „< 

•al  f  I 


S 

"O 

•3 

S.2 

15 
11 


•SCI 

sS^ 

ilo 

fir 

ir 


till! 


«  o  S  u'S 


-ll-ssissa 

M    9*-gg«l! 

-lilt 


CH.  XXV.]  CARBONIFEROUS   GROUP.  393 

steep,  and  lofty  parallel  ridges  of  the  Alleghany  mountains.  The 
out-crop  of  the  strata  in  these  ridges,  like  the  two  belts  of  hypogene 
and  newer  rocks  (A  B,  and  B  c),  above  alluded  to,  when  laid  down 
on  a  geological  map,  exhibit  long  stripes  of  different  colours,  run- 
ning in  a  N.E.  and  S.W.  direction,  in  the  same  way  as  the  lias, 
chalk,  and  other  secondary  formations  in  the  middle  and  eastern  half 
of  England. 

The  narrow  and  parallel  zones  of  the  Appalachians,  here  men- 
tioned, consist  of  strata,  folded  into  a  succession  of  convex  and  con- 
cave flexures,  subsequently  laid  open  by  denudation.  The  compo- 
nent rocks  are  of  great  thickness,  all  referable  to  the  Silurian, 
Devonian,  and  Carboniferous  formations.  There  is  no  principal  or 
central  axis,  as  in  the  Pyrenees  and  many  other  chains  —  no  nucleus 
to  which  all  the  minor  ridges  conform;  but  the  chain  consists  of 
many  nearly  equal  and  parallel  foldings,  having  what  is  termed  an 
anticlinal  and  synclinal  arrangement  (see  above,  p.  48.).  This  sys- 
tem of  hills  extends,  geologically  considered,  from  Vermont  to  Ala- 
bama, being  more  than  100  miles  long,  from  50  to  150  miles  broad,  and 
varying  in  height  from  2000  to  6000  feet.  Sometimes  the  whole  as- 
semblage of  ridges  runs  perfectly  straight  for  a  distance  of  more  than 
50  miles,  after  which  all  of  them  wheel  round  altogether,  and  take  a 
new  direction,  at  an  angle  of  20  or  30  degrees  to  the  first. 

We  are  indebted  to  the  state  surveyors  of  Virginia  and  Pennsyl- 
vania, Prof.  W.  B.  Eogers  and  his  brother  Prof.  H.  D.  Rogers,  for 
the  important  discovery  of  a  clue  to  the  general  law  of  structure 
prevailing  throughout  this  range  of  mountains,  which,  however  sim- 
ple it  may  appear  when  once  made  out  and  clearly  explained,  might 
long  have  been  overlooked,  amidst  so  great  &  mass  of  complicated 
details.  It  appears  that  the  bending  and  fracture  of  the  beds  is 
greatest  on  the  south-eastern  or  Atlantic  side  of  the  chain,  and  the 
strata  become  less  and  less  disturbed  as  we  go  westward,  until  at 
length  they  regain  their  original  or  horizontal  position.  By  refer- 
ence to  the  section  (fig.  505.),  it  will  be  seen  that  on  the  eastern  side, 
or  in  the  ridges  and  troughs  nearest  the  Atlantic,  south-eastern  dips 
predominate,  in  consequence  of  the  beds  having  been  folded  back 
upon  themselves,  as  in  i,  those  on  the  north-western  side  of  each 
arch  having  been  inverted.  The  next  set  of  arches  (such  as  k)  are 
more  open,  each  having  its  western  side  steepest ;  the  next  (I)  open 
out  still  more  widely,  the  next  (m)  still  more,  and  this  continues 
until  we  arrive  at  the  low  and  level  part  of  the  Appalachian  coal- 
field (D  E). 

In  nature  or  in  a  true  section,  the  number  of  bendings  or  parallel 
folds  is  so  much  greater  that  they  could  not  be  expressed  in  a  dia- 
gram without  confusion.  It  is  also  clear  that  large  quantities  of 
rock  have  been  removed  by  aqueous  action  or  denudation,  as  will 
appear  if  we  attempt  to  complete  all  the  curves  in  the  manner  indi- 
cated by  the  dotted  lines  at  i  and  k. 

The  movements  which  imparted  so  uniform  an  order  of  arrange- 
ment to  this  vast  system  of  rocks  must  have  been,  if  not  contempo- 


394  APPALACHIAN   CHAIN.  [Cn.  XXV. 

raneous.  at  least  parts  of  one  and  the  same  series,  depending  on  some 
common  cause.  Their  geological  date  is  well  defined,  at  least  within 
certain  limits,  for  they  must  have  taken  place  after  the  deposition  of 
the  carboniferous  strata  (No.  5.),  and  before  the  formation  of  the  red 
sandstone  (No.  4.).  The  greatest  disturbing  and  denuding  forces 
have  evidently  been  exerted  on  the  south-eastern  side  of  the  chain ; 
and  it  is  here  that  igneous  or  plutonic  rocks  are  observed  to  have 
invaded  the  strata,  forming  dykes,  some  of  which  run  for  miles  in 
lines  parallel  to  the  main  direction  of  the  Appalachians,  or  N.N.E. 
and  S.S.W. 

The  thickness  of  the  carboniferous  rocks  in  the  region  c  is  very 
great,  and  diminishes  rapidly  as  we  proceed  to  the  westward.  The 
surveys  of  Pennsylvania  and  Virginia  show  that  the  south-east  was 
the  quarter  whence  the  coarser  materials  of  these  strata  were  derived, 
so  that  the  ancient  land  lay  in  that  direction.  The  conglomerate 
which  forms  the  general  base  of  the  coal-measures  is  1500  feet  thick 
in  the  Sharp  Mountain,  where  I  saw  it  (at  c)  near  Pottsville ;  whereas 
it  has  only  a  thickness  of  500  feet,  about  thirty  miles  to  the  north- 
west, and  dwindles  gradually  away  when  followed  still  farther  in  the 
same  direction,  until  its  thickness  is  reduced  to  30  fe,et.*  The  lime- 
stones, on  the  other  hand,  of  the  coal-measures  augment  as  we  trace 
them  westward.  Similar  observations  have  been  made  in  regard  to 
the  Silurian  and  Devonian  formations  in  New  York ;  the  sandstones 
and  all  the  mechanically-formed  rocks  thinning  out  as  they  go  west- 
ward, and  the  limestones  thickening,  as  it  were,  at  their  expense.  It 
is,  therefore,  clear  that  the  ancient  land  was  to  the  east,  where  the 
Atlantic  now  is ;  the  deep  sea,  with  its  banks  of  coral  and  shells  to 
the  west,  or  where  the  hydrographical  basin  of  the  Mississippi  is 
now  situated. 

In  that  region,  near  Pottsville,  where  the  thickness  of  the  coal- 
measures  is  greatest,  there  are  thirteen  seams  of  anthracitic  coal, 
several  of  them  more  than  2  yards  thick.  Some  of  the  lowest  of 
these  alternate  with  beds  of  white  grit  and  conglomerate  of  coarser 
grain  than  I  ever  saw  elsewhere,  associated  with  pure  coal.  The  peb- 
bles of  quartz  are  often  of  the  size  of  a  hen's  egg.  On  following  these 
pudding-stones  and  grits  for  several  miles  from  Pottsville,  by  Tarna- 
qua,  to  the  Lehigh  Summit  Mine,  in  company  with  Mr.  H.  D. 
Eogers,  in  1841,  he  pointed  out  to  me  that  the  coarse-grained  strata 
and  their  accompanying  shales  gradually  thin  out,  until  seven  seams 
of  coal,  at  first  widely  separated,  are  brought  nearer  and  nearer 
together,  until  they  successively  unite ;  so  that  at  last  they  form 
one  mass,  between  40  and  50  feet  thick.  I  saw  this  enormous  bed  of 
anthracitic  coal  quarried  in  the  open  air  at  Mauch  Chunk  (or  the 
Bear  Mountain),  the  overlying  sandstone,  40  feet  thick,  having  been 
removed  bodily  from  the  top  of  the  hill,  which,  to  use  the  miner's 
expression,  had  been  "scalped."  The  accumulation  of  vegetable 
matter  now  constituting  this  vast  bed  of  anthracite,  may  perhaps, 

*  H.  D.  Eogers,  Trans.  Assoc.  Amer.  Geol.,  1840-42,  p.  440. 


CH.  XXV.] 


UNION   OF   COAL   SEAMS. 


395 


before  it  was  condensed  by  pressure  and  the  discharge  of  its 
hydrogen,  oxygen,  and  other  volatile  ingredients,  have  been  between 
200  and  300  feet  thick.  The  origin  of  such  a  vast  thickness  of 
vegetable  remains,  so  unmixed  with  earthy  ingredients,  can,  I  think, 
be  accounted  for  in  no  other  way,  than  by  the  .growth,  during  thou- 
sands of  years,  of  trees  and  ferns,  in  the  manner  of  peat,  —  a  theory 
which  the  presence  of  the  Stigmaria  in  situ  under  each  of  the  seven 
layers  of  anthracite,  fully  bears  out.  The  rival  hypothesis,  of  the 
drifting  of  plants  into  a  sea  or  estuary,  leaves  the  absence  of  sedi- 
ment, or,  in  this  case  of  sand  and  pebbles,  wholly  unexplained. 

But  the  student  will  naturally  ask,  what  can  have  caused  so  many 
seams  of  coal,  after  they  had  been  persistent  for  miles,  to  come  to- 
gether and  blend  into  one  single  seam,  and  that  one  equal  in  the 
aggregate  to  the  thickness  of  the  several  separate  seams  ?  Often  had 
the  same  question  been  put  by  English  miners  before  a  satisfactory 
answer  was  given  to  it  by  the  late  Mr.  Bowman.  The  following  is 
his  solution  of  the  problem.  Let  a  a',  fig.  506.,  be  a  mass  of  vege- 

Fig.  506. 


Fig.  507. 


table  matter,  capable,  when  condensed,  of  forming  a  3-foot  seam  of 
coal.  It  rests  on  the  underclay  b  b',  filled  with  roots  of  trees  in  situ, 
and  it  supports  a  growing  forest  (c  D).  Suppose  that  part  of  the 
same  forest  D  E  had  become  submerged  by  the  ground  sinking  down 
25  feet,  so  that  the  trees  have  been  partly  thrown  down  and  partly 
remain  erect  in  water,  slowly  decaying,  their  stumps  and  the  lower 
parts  of  their  trunks  being  enveloped  in  layers  of  sand  and  mud, 
which  are  gradually  filling  up  the  lake  D  F.  When  this  lake  or 
lagoon  has  at  length  been  entirely  silted  up  and  converted  into  land, 
say,  in  the  course  of  a  century,  the  forest  c  D  will  extend  once  more 
continuously  over  the  whole  area  c  F,  as  in  fig.  507.,  and  another  mass 
of  vegetable  matter  (g  g'\  forming  3  feet  more  of  coal,  may  accu- 
mulate from  c  to  F.  We  then  find  in  the  region  F,  two  seams  of 
coal  (a!  and  g')  each  3  feet  thick,  and  separated  by  25  feet  of  sand- 
stone and  shale,  with  erect  trees  based  upon  the  lower  coal,  while, 
between  D  and  c,  we  find  these  two  seams  united  into  a  2-yard  coal. 
It  may  be  objected  that  the  uninterrupted  growth  of  plants  during 
the  interval  of  a  century  will  have  caused  the  vegetable  matter  in 


396  HORIZONTAL   COAL   STRATA.  [Cn.  XXV. 

the  region  c  D  to  be  thicker  than  the  two  distinct  seams  a'  and  g'  at 
F  ;  and  no  doubt  there  would  actually  be  a  slight  excess  representing 
one  generation  of  trees  with  the  remains  of  other  plants,  forming 
half  an  inch  or  an  inch  of  coal;  but  this  would  not  prevent  the 
miner  from  affirming  that  the  seam  a  g,  throughout  the  area  c  D, 
was  equal  to  the  two  seams  a'  and  g'  at  F. 

The  reader  has  seen,  by  reference  to  the  section  (fig.  505.  p. 
392.),  that  the  strata  of  the  Appalachian  coal-field  assume  an 
horizontal  position  west  of  the  mountains.  In  that  less  elevated 
country,  the  coal-measures  are  intersected  by  three  great  navigable 
rivers,  and  are  capable  of  supplying  for  ages,  to  the  inhabitants  of  a 
densely  peopled  region,  an  inexhaustible  supply  of  fuel.  These 
rivers  are  the  Monongahela,  the  Alleghany,  and  the  Ohio,  all  of 
which  lay  open  on  their  banks  the  level  seams  of  coal.  Looking 
down  the  first  of  these  at  Brownsville,  we  have  a  fine  view  of  the 
main  seam  of  bituminous  coal  10  feet  thick,  commonly  called  the 
Pittsburg  seam,  breaking  out  in  the  steep  cliff  at  the  water's  edge ; 
and  I  made  the  accompanying  sketch  of  its  app§arance  from  the 
bridge  over  the  river  (see  fig.  508.).  Here  the  coal,  10  feet  thick,  is 
covered  by  carbonaceous  shale  (£»),  and  this  again  by  micaceous  sand- 
stone (c).  Horizontal  galleries  may  be  driven  everywhere  at  very 
slight  expense,  and  so  worked  as  to  drain  themselves,  while  the  cars, 
laden  with  coal  and  attached  to  each  other,  glide  down  on  a  railway, 
so  as  to  deliver  their  burden  into  barges  moored  to  the  river's  bank. 
The  same  seam  is  seen  at  a  distance,  on  the  right  bank  (at  «),  and 
may  be  followed  the  whole  way  to  Pittsburg,  fifty  miles  distant.  As 
it  is  nearly  horizontal,  while  the  river  descends  it  crops  out  at  a  con- 
tinually increasing,  but  never  at  an  inconvenient,  height  above  the 
Monongahela.  Below  the  great  bed  of  coal  at  Brownsville  is  a  fire- 
clay 18  inches  thick,  and  below  this,  several  beds  of  limestone,  below 
which  again  are  other  coal  seams.  I  have  also  shown  in  my  sketch 
another  layer  of  workable  coal  (at  d  d\  which  breaks  out  on  the 
slope  of  the  hills  at  a  greater  height.  Here  almost  every  proprietor 
can  open  a  coal-pit  on  his  own  land,  and  the  stratification  being  very 
regular,  he  may  calculate  with  precision  the  depth  at  which  coal  may 
be  won. 

The  Appalachian  coal-field,  of  which  these  strata  form  a  part 
(from  c  to  E,  section,  fig.  505.,  p.  392.),  is  remarkable  for  its  vast 
area  ;  for,  according  to  Professor  H.  D.  Rogers,  it  stretches  continu- 
ously from  N.E.  to  S.W.,  for  a  distance  of  720  miles,  its  greatest 
width  being  about  180  miles.  On  a  moderate  estimate,  its  superficial 
area  amounts  to  63,000  square  miles. 

This  coal-formation,  before  its  original  limits  were  reduced  by 
denudation,  must  have  measured  900  miles  in  length,  and  in  some 
places  more  than  200  miles  in  breadth.  By  again  referring  to  the 
section  (fig.  505.,  p.  392.),  it  will  be  seen  that  the  strata  of  coal  are 
horizontal  to  the  westward  of  the  mountains  in  the  region  DE,  and 
become  more  and  more  inclined  and  folded  as  we  proceed  eastward. 
Now  it  is  invariably  found,  as  Professor  H.  D.  Rogers  has  shown  by 


APPALACHIAN   COAL    STRATA. 


397 


chemical  analysis,  that  the  coal  is  most  bituminous  towards  its 
western  limit,  where  it  remains  level  and  unbroken,  and  that  it 
becomes  progressively  debituminized  as  we  travel  south-eastward 
towards  the  more  bent  and  distorted  rocks.  Thus,  on  the  Ohio,  the 
proportion  of  hydrogen,  oxygen,  and  other  volatile  matters  ranges 
from  forty  to  fifty  per  cent.  Eastward  of  this  line,  on  the  Mononga- 


398  CONVEKSION   OF   COAL   INTO   LIGNITE.         [Cn.  XXV. 

hela,  it  still  approaches  forty  per  cent.,  where  the  strata  begin  to  ex- 
perience some  gentle  flexures.  On  entering  the  Alleghany  Moun- 
tains, where  the  distinct  anticlinal  axes  begin  to  show  themselves, 
but  before  the  dislocations  are  considerable,  the  volatile  matter  is 
generally  in  the  proportion  of  eighteen  or  twenty  per  cent.  At 
length,  when  we  arrive  at  some  insulated  coal-fields  (5',  fig.  505.)  as- 
sociated with  the  boldest  flexures  of  the  Appalachian  chain,  where 
the  strata  have  been  actually  turned  over,  as  near  Pottsville,  we 
find  the  coal  to  contain  only  from  six  to  twelve  per  cent,  of  bitumen, 
thus  becoming  a  genuine  anthracite.* 

It  appears  from  the  researches  of  Liebig  and  other  eminent 
chemists,  that  when  wood  and  vegetable  matter  are  buried  in  the 
earth  exposed  to  moisture,  and  partially  or  entirely  excluded  from 
the  air,  they  decompose  slowly  and  evolve  carbonic  acid  gas,  thus 
parting  with  a  portion  of  their  original  oxygen.  By  this  means, 
they  become  gradually  converted  into  lignite  or  wood-coal,  which 
contains  a  larger  proportion  of  hydrogen  than  wood  does.  A  con- 
tinuance of  decomposition  changes  this  lignite  into  common  or  bitu- 
minous coal,  chiefly  by  the  discharge  of  carburetted  hydrogen,  or  the 
gas  by  which  we  illuminate  our  streets  and  houses.  According  to 
Bischoff,  the  inflammable  gases  which  are  always  escaping  from 
mineral  coal,  and  are  so  often  the  cause  of  fatal  accidents  in  mines, 
always  contain  carbonic  acid,  carburetted  hydrogen,  nitrogen,  and 
olifiant  gas.  The  disengagement  of  all  these  gradually  transforms 
ordinary  or  bituminous  coal  into  anthracite,  to  which  the  various 
names  of  splint-coal,  glance-coal,  hard-coal,  culm,  and  many  others, 
have  been  given. 

We  have  seen  that,  in  the  Appalachian  coal-field,  there  is  an 
intimate  connection  between  the  extent  to  which  the  coal  has  parted 
with  its  gaseous  contents,  and  the  amount  of  disturbance  which  the 
strata  have  undergone.  The  coincidence  of  these  phenomena  may 
be  attributed  partly  to  the  greater  facility  afforded  for  the  escape  of 
volatile  matter,  where  the  fracturing  of  the  rocks  had  produced  an 
infinite  number  of  cracks  and  crevices,  and  also  to  the  heat  of  the 
gases  and  water  penetrating  these  cracks,  when  the  great  movements 
took  place,  which  have  rent  and  folded  the  Appalachian  strata.  It 
is  well  known  that,  at  the  present  period,  thermal  waters  and  hot 
vapours  burst  out  from  the  earth  during  earthquakes,  and  these 
would  not  fail  to  promote  the  disengagement  of  volatile  matter  from 
the  carboniferous  rocks. 

Continuity  of  seams  of  coal. — As  single  seams  of  coal  are  con- 
tinuous over  very  wide  areas,  it  has  been  asked,  how  forests  could 
have  prevailed  uninterruptedly  over  such  wide  spaces.  In  reply,  it 
may  be  said  that  swamp-forests  in  one  delta  may  extend  for  25,  50, 
or  100  miles,  while  in  a  contiguous  delta,  as  on  the  borders  of  the 
Gulf  of  Mexico,  another  of  precisely  the  same  character  may  be 
growing ;  and  these  may  in  after  ages  appear  to  geologists  to  have 

*  Trans,  of  Assoc.  of  Amer.  Geol.,  p.  470. 


CH.  XXV.]  CLIMATE   OF    COAL   PERIOD.  399 

been  continuous,  although  in  fact  they  were  simply  contemporaneous. 
Denudation  may  easily  be  imagined  in  such  cases  as  the  cause  of  in- 
terruptions, which  were  in  fact,  original.  But  as  in  all  the  American 
coal-fields  there  are  numerous  root-beds  without  any  superincumbent 
coal,  we  may  presume  that  frequently  layers  of  vegetable  matter 
were  removed  by  floods ;  and  in  other  cases,  where  the  stigmaria-clays 
are  for  a  certain  space  covered  with  coal,  and  then  prolonged  with- 
out any  such  covering,  the  inference  of  partial  denudation  is  still 
more  obvious. 

In  the  Forest  of  Dean,  ancient  river-channels  are  found,  which 
pass  through  beds  of  coal,  and  in  which  rounded  pebbles  of  coal 
occur.  They  are  of  older  date  than  the  overlying  and  undisturbed 
coal-measures.  The  late  Mr.  Buddie,  who  described  them  to  me, 
told  me  he  had  seen  similar  phenomena  in  the  Newcastle  coal-field. 
Nevertheless,  instances  of  these  channels  are  much  more  rare  than 
we  might  have  anticipated,  especially  when  we  remember  how  often 
the  roots  of  trees  (Stigmarice)  have  been  torn  up,  and  drifted  in 
broken  fragments  into  the  grits  and  sandstones.  The  prevalence  of 
a  downward  movement  is,  no  doubt,  the  principal  cause  which  has 
saved  so  many  extensive  seams  of  coal  from  destruction  by  fluviatile 
action. 

Climate  of  Coal  Period.  —  So  long  as  the  botanist  taught  that  a 
tropical  climate  was  implied  by  the  carboniferous  flora,  geologists 
might  well  be  at  a  loss  to  reconcile  the  preservation  of  so  much  vege- 
table matter  with  a  high  temperature ;  for  heat  hastens  the  decompo- 
sition of  fallen  leaves  and  trunks  of  trees,  whether  in  the  atmosphere 
or  in  water.  It  is  well  known  that  peat,  so  abundant  in  the  bogs  of 
high  latitudes,  ceases  to  grow  in  the  swamps  of  warmer  regions. 
It  seems,  however,  to  have  become  a  more  and  more  received  opinion, 
that  the  coal-plants  do  not,  on  the  whole,  indicate  a  climate  resem- 
bling that  now  enjoyed  in  the  equatorial  zone.  Tree-ferns  range  as 
far  south  as  the  southern  part  of  New  Zealand,  and  Araucarian  pines 
occur  in  Norfolk  Island.  A  great  predominance  of  ferns  and  lyco- 
podiums  indicates  moisture,  equability  of  temperature,  and  freedom 
from  frost,  rather  than  intense  heat ;  and  we  know  too  little  of  the 
sigillariae,  calamites,  asterophyllites,  and  other  peculiar  forms  of  the 
carboniferous  period,  to  be  able  to  speculate  with  confidence  on  the 
kind  of  climate  they  may  have  required. 

The  same  may  be  said  of  the  corals  and  cephalopoda  of  the 
Mountain  Limestone, — they  belong  to  families  of  whose  climatal 
habits  we  know  nothing ;  and  even  if  they  should  be  thought  to 
imply  that  a  warm  temperature  characterized  the  northern  seas  in 
the  carboniferous  era,  the  absence  of  cold  may  have  given  rise  (as  at 
present  in  the  seas  of  the  Bermudas,  under  the  influence  of  the 
gulf-stream)  to  a  very  wide  geographical  range  of  stone-building 
corals  and  shell-bearing  cuttle-fish,  without  its  being  necessary  to 
call  in  the  aid  of  tropical  heat. 


400  CARBONIFEROUS   REPTILES.  [Csv  XXV. 

CARBONIFEROUS   REPTILES. 

Where  we  have  evidence  in  a  single  coal-field,  as  in  that  of  Nova 
Scotia,  or  of  South  Wales,  of  fifty  or  even  a  hundred  ancient  forests 
buried  one  above  the  other,  with  the  roots  of  trees  still  in  their 
original  position,  and  with  some  of  the  trunks  still  remaining  erect, 
we  are  apt  to  wonder  that  until  the  year  1844  no  remains  of  contem- 
poraneous air-breathing  creatures  should  have  been  discovered.  No 
vertebrated  animals  more  highly  organized  than  fish,  no  mammalia 
or  birds,  no  saurians,  frogs,  tortoises,  or  snakes  were  known  in  rocks 
of  such  high  antiquity.  In  the  coal-fields  of  Europe  mention  has 
been  made  of  beetles,  locusts,  and  a  few  other  insects,  but  no  land- 
shells  have  even  now  been  met  with.  Agassiz  described  in  his  great 
work  on  fossil  fishes  more  than,  one  hundred  and  fifty  species  of  ich- 
thyolites  from  the  coal-strata,  ninety-four  belonging  to  the  families  of 
shark  and  ray,  and  fifty-eight  to  the  class  of  ganoids.  Some  of  these 
fish  are  very  remote  in  their  organization  from  any  now  living,  espe- 
cially those  of  the  family  called  Sauroid  by  Agassiz  ;  as  Megalich- 
thys,  Holoptychius,  and  others,  which  were  often  of  great  size,  and  all 
predaceous.  Their  osteology,  says  M.  Agassiz,  reminds  us  in  many 
respects  of  the  skeletons  of  saurian  reptiles, 
both  by  the  close  sutures  of  the  bones  of  the 
skull,  their  large  conical  teeth  striated  longitu- 
dinally (see  fig.  509.),  the  articulations  of  the 
spinous  processes  with  the  vertebrae,  and  other 
characters.  Yet  they  do  not  form  a  family  in- 
termediate between  fish  and  reptiles,  but  are 
true  Jish,  though  doubtless  more  highly  or- 
ganized than  any  living  fish.* 

The  annexed  figure  represents  a  large  tooth 
of  the  Holoptychius,  found  by  Mr.  Horner  in  the 
Cannel  coal  of  Fifeshire.  This  fish  probably  in- 
habited an  estuary,  like  many  of  its  contempo- 
raries, and  frequented  both  rivers  and  the  sea. 

At  length,  in  1844,  the  first  skeleton  of  a  true 
Ag.  reptile  was  announced  from  the  coal  of  Miinster- 
coai-fieid.        Appel  in  Rhenish  Bavaria,  by  H.  von  Meyer, 

Tooth ;  natural  size.  »  <r      * 

under  the  name  of  Apateon  pedestris,  the 
animal  being  supposed  to  be  nearly  related  to  the  salamanders.  Three 
years  later,  in  1847,  Prof,  von  Dechen  found  in  the  coal-field  of 
Saarbriick,  at  the  village  of  Lebach,  between  Strasburg  and  Treves, 
the  skeletons  of  no  less  than  three  distinct  species  of  air-breath- 
ing reptiles,  which  were  described  by  the  late  Prof.  Goldfuss 
under  the  generic  name  of  Archegosaurus.  The  ichthyolites  and 
plants  found  in  the  same  strata  left  no  doubt  that  these  remains 
belonged  to  the  true  coal  period.  The  skulls,  teeth,  and  the  greater 
portions  of  the  skeleton,  nay,  even  a  large  part  of  the  skin,  of  two 

*  Agassiz,  Poiss.  Foss.  vol.  ii.  p.  88,  &c. 


CH.  XXV.] 


CARBONIFEROUS   REPTILES. 


401 


Fig.  510. 


of  these  reptiles  have  been 
faithfully  preserved  in  the 
centre  of  spheroidal  con- 
cretions of  clay-iron-stone. 
The  largest  of  these  lizards, 
Archegosaurus       Decheni, 
must  have   been  3  feet  6 
inches  long.     The  annexed 
drawing     represents      the 
skull   and    neck   bones   of 
the  smallest  of  the  three, 
of  the  natural  size.     They 
were  considered  by  Gold- 
fuss   as   saurians,    but   by 
Herman  von  Meyer  as  most 
nearly  allied  to  the  Laby- 
rinthodon,  and  therefore,  as 
before  explained  (p.  342.), 
having     many    characters 
intermediate   between   ba- 
trachians      and     saurians. 
The  remains  of  the  extre- 
mities leave  no  doubt  that 
they      were     quadrupeds, 
"  provided,"      says      Von 
Meyer,   "  with    hands  and 
feet  terminating  in  distinct 
toes ;  but  these  limbs  were  weak,   serving  only   for   swimming  or 
creeping."     The  same  anatomist  has  pointed  out  certain  points  of 

analogy  between  their  bones  and 
those  of  the  Proteus  anguinus  ;  and 
Prof.  Owen  has  observed  to  me  that 
they  make  an  approach  to  the  Pro- 
teus in  the  shortness  of  their  ribs. 
Two  specimens  of  these  ancient  rep- 
tiles retain  a  large  part  of  the  outer 
skin,  which  consisted  of  long,  nar- 
row wedge-shaped,  tile-like,  and  horny  scales,  arranged  in  rows 
(see  fig.  511.). 

Cheirotherian  footprints  in  coal-measures.  United  States.  —  In 
1844,  the  very  year  when  the  Apateon  or  Salamander  of  the  coal 
was  first  met  with  in  the  country  between  the  Moselle  and  the 
Rhine,  Dr.  King  published  an  account  of  the  footprints  of  a  large 
reptile  discovered  by  him  in  North  America.  These  occur  in  the 
coal-strata  of  Greensburg,  in  "Westmoreland  County,  Pennsylvania  ; 
and  I  had  an  opportunity  of  examining  them  in  1846.  I  was  at  once 
convinced  of  their  genuineness,  and  declared  my  conviction  on  that 

*  Goldfuss,  Neue  Jenaische  Lit.  Zeit.,  1848  ;  and  Von  Meyer,  Quart.  Geol. 
Journ.,  vol.  iv.  Miscell.  p.  51. 

D   D 


Archegosaurus  minor,  Goldfuss.    Fossil  reptile  from 
the  coal-measures,  Saarbriick. 


Fig.  511. 


Imbricated  covering  of  skin  of  Archego- 
saurus medius,  Goldf.  ; 
magnified.* 


402 


FOOTPRINTS   OF 


[Cn.  XXV. 


point,  on  which  doubts  had  been  entertained  both  in  Europe  and  the 
United  States.  The  footmarks  were  first  observed  standing  out  in 
relief  from  the  lower  surface  of  slabs  of  sandstone,  resting  on  thin 
layers  of  fine  unctuous  clay.  I  brought  away  one  of  these  masses, 
which  is  represented  in  the  accompany  drawing  (fig.  512.).  It  dis- 


Fig.  512. 


Scale  one-sixth  the  original. 

Slab  of  sandstone  from  the  coal-measures  of  Pennsylvania,  with  footprints  of 
air-breathing  reptile  and  casts  of  cracks. 

plays,  together  with  footprints,  the  casts  of  cracks  («,  of)  of  various 
sizes.  The  origin  of  such  cracks  in  clay,  and  casts  of  the  same,  has 
before  been  explained,  and  referred  to  the  drying  and  shrinking  of 
mud,  and  the  subsequent  pouring  of  sand  into  open  crevices.  It  will 
be  seen  that  some  of  the  cracks,  as  at  b,  c,  traverse  the  footprints, 
and  produce  distortion  in  them,  as  might  have  been  expected,  for  the 
mud  must  have  been  soft  when  the  animal  walked  over  it  and  left 
the  impressions  ;  whereas,  when  it  afterwards  dried  up  and  shrank, 
it  would  be  too  hard  to  receive  such  indentations. 

No  less  than  twenty-three  footsteps  were  observed  by  Dr.  King  in 


CH.  XXV.]  AIR-BREATHING   REPTILES.  403 

the  same  quarry  before  it  was  abandoned,  the  greater  part  of  them 
so  arranged  (see  fig.  513.)  on  the  surface  of  one  stratum  as  to  imply 


Fig.  513. 


Series  of  reptilian  footprints  in  the  coal-strata  of  "WestnToreland 

County,  Pennsylvania. 

a.  Mark  of  nail  ? 

that  they  were  made  successively  by  the  same  animal.  Everywhere 
there  was  a  double  row  of  tracks,  and  in  each  row  they  occur  in 
pairs,  each  pair  consisting  of  a  hind  and  fore  foot,  and  each  being  at 
nearly  equal  distances  from  the  next  pair.  In  each  parallel  row  the 
toes  turn  the  one  set  to  the  right,  the  other  to  the  left.  In  the 
European  Cheirotherium,  before  mentioned  (p.  339.),  both  the  hind 

D  D  2 


404  FOOTPRINTS   OF   REPTILIANS.  [Cn.  XXV. 

and  the  fore  feet  have  each  five  toes,  and  the  size  of  the  hind  foot  is 
about  five  times  as  large  as  the  fore  foot.  In  the  American  fossil 
the  posterior  footprint  is  not  even  twice  as  large  as  the  anterior, 
and  the  number  of  toes  is  unequal,  being  five  in  the  hinder  and  four 
in  the  anterior  foot.  In  this,  as  in  the  European  Cheirotherium,  one 
toe  stands  out  like  a  thumb,  and  these  thumb-like  toes  turn  the  one 
set  to  the  right,  and  the  other  to  the  left.  The  American  Cheiro- 
therium  was  evidently  a  broader  animal,  and  belonged  to  a  distinct 
genus  from  that  of  the  triassic  age  in  Europe.* 

We  may  assume  that  the  reptile  which  left  these  prints  on  the 
ancient  sands  of  the  coal-measures  was  an  air-breather,  because  its 
weight  would  not  have  been  sufficient  under  water  to  have  made 
impressions  so  deep  and  distinct.  The  same  conclusion  is  also  borne 
out  by  the  casts  of  the  cracks  above  described,  for  they  show  that 
the  clay  had  been  exposed  to  the  air  and  sun,  so  as  to  have  dried  and 
shrunk. 

The  geological  position  of  the  sandstone  of  Greensburg  is  perfectly 
clear,  being  situated  in  the  midst  of  the  Appalachian  coal-field, 
having  the  main  bed  of  coal,  called  the  Pittsburg  seam,  above  men- 
tioned (p.  396.),  3  yards  thick,  100  feet  above  it,  and  worked  in  the 
neighbourhood,  with  several  other  seams  of  coal  at  lower  levels. 
The  impressions  of  Lepidodendron,  Sigillaria,  Stigmaria,  and  other 
characteristic  carboniferous  plants  are  found  both  above  and  below 
the  level  of  the  reptilian  footsteps. 

Analogous  footprints  of  a  large  reptile  of  still  older  date  were 
afterwards  found  (1849)  at  Pottsville,  70  miles  N.E.  of  Philadelphia, 
by  Mr.  Isaac  Lea,  in  a  formation  of  red  shales,  called  No.  XL  by 
Prof.  H.  D.  Rogers,  in  the  State  Survey  of  Pennsylvania,  and  re- 
ferred by  him  to  the  base  of  the  coal,  but  regarded  by  some  geolo- 
gists as  the  uppermost  part  of  the  Old  Red  Sandstone.  A  thickness 
of  1700  feet  of  strata  intervenes  between  the  footprints  of  Greens - 
burg,  before  described,  and  these  older  Pottsville  impressions.  In 
the  same  Red  Shale,  No.  XX,  the  "  debateable  ground "  between 
the  Carboniferous  and  Devonian  group,  Prof.  H.  D.  Rogers  an- 
nounced in  1851  that  he  had  discovered  other  footprints,  referred 
by  him  to  three  species  of  quadrupeds,  all  of  them  five-toed  and  in 
double  rows,  with  an  opposite  symmetry,  as  if  made  by  right  and 
left  feet,  while  they  likewise  display  the  alternation  of  fore  foot  and 
hind  foot.  One  species,  the  largest  of  the  three,  presents  a  diameter 
for  each  footprint  of  about  two  inches,  and  shows  the  fore  and  hind 
feet  to  be  nearly  equal  in  dimensions.  It  exhibits  a  length  of  stride 
of  about  nine  inches,  and  a  breadth  between  the  right  and  left  foot- 
steps of  nearly  four  inches.  The  impressions  of  the  hind  feet  are  but 
little  in  the  rear  of  the  fore  feet.  The  animal  which  made  them  is 
supposed  to  have  been  allied  to  a  Saurian,  rather  than  to  a  Batra- 
chian  or  Chelonian.  With  these  footmarks  were  seen  shrinkage 
cracks,  such  as  are  caused  by  the  sun's  heat  in  mud,  and  rain-spots, 
with  the  signs  of  the  trickling  of  water  on  a  wet,  sandy  beach ;  all 
*  See  Lyell's  Second  Visit,  &c.,  vol.  ii.  p.  305. 


CH.  XXV.]  AIR-BREATHERS   IN   THE    COAL.  405 

confirming  the  conclusion  derived  from  the  footprints,  that  the 
quadrupeds  belonged  to  air-breathers,  and  not  to  aquatic  races. 

In  1852  the  first  osseous  remains  of  a  reptile  were  obtained  from 
the  coal-measures  of  America  by  Mr.  Dawson  and  myself.  We  de- 
tected them  in  the  interior  of  one  of  the  erect  Sigillariae  before  al- 
luded to  as  of  such  frequent  occurrence  in  Nova  Scotia.  The  tree 
was  about  two  feet  in  diameter,  and  consisted,  as  usual,  of  an  ex- 
ternal cylinder  of  bark,  converted  into  coal,  and  an  internal  stony 
axis  of  black  sandstone,  or  rather  mud  and  sand  stained  black  by 
carbonaceous  matter,  and  cemented  together  with  fragments  of  wood 
into  a  rock.  These  fragments  were  in  the  state  of  charcoal,  and 
seem  to  have  fallen  to  the  bottom  of  the  hollow  tree  while  it  was 
rotting  away.  The  skull,  jaws,  and  vertebras  of  a  reptile,  probably 
about  2^  feet  in  length  (Dendrerpeton  Acadianum,  Owen),  were 
scattered  through  this  stony  matrix.  The  shell  also  of  a  Pupa,  the 
first  pulmoniferous  mollusk  ever  met  with  in  the  coal,  was  observed 
in  the  same  stony  mass.  Dr.  Wyman  of  Boston  pronounced  the 
reptile  to  be  allied  in  structure  to  Menobranchus  and  Menopoma, 
species  of  batrachians,  now  inhabiting  the  North  American  rivers. 
The  same  view  was  afterwards  confirmed  by  Prof.  Owen,  who  also 
pointed  out  the  resemblance  of  the  cranial  plates  to  those  seen  in  the 
skull  of  Archegosaurus  and  Labyrinthodon.*  Whether  the  creature 
had  crept  into  the  hollow  tree  while  its  top  was  still  open  to  the  air, 
or  whether  it  was  washed  in  with  mud  during  a  flood,  or  in  what- 
ever other  manner  it  entered,  must  be  matter  of  conjecture. 

Footprints  of  two  reptiles  of  different  sizes  had  previously  been 
observed  by  Dr.  Harding  and  Dr.  Gesner  on  ripple-marked  flags  of 
the  lower  coal-measures  in  Nova  Scotia,  evfdently  made  by  quad- 
rupeds walking  on  the  ancient  beach,  or  out  of  the  water,  just  as  the 
recent  Menopoma  is  sometimes  observed  to  do. 

In  1853  Prof.  Owen  announced  the  first  discovery  of  fossil  rep- 
tilian remains  in  the  British  Coal-Measures ;  and,  in  1854,  the  same 
osteologist  described  a  "  sauroid  batrachian,"  of  the  Labyrinthodon 
family,  obtained  by  Mr.  Dawson,  from  the  coal  of  Pictou  in  Nova 
Scotia. 

Thus  in  ten  years  (between  1844  and  1854)  the  skeletons  or  bones 
of  no  less  than  seven  carboniferous  reptiles,  referred  to  five  genera, 
were  brought  to  light ;  to  say  nothing  of  numerous  reptilian  foot- 
prints, some  of  them  too  large  to  belong  to  the  same  species  as  the 
bones. 

Rarity  of  vertebrate  and  invertebrate  Air-breathers  in  Coal. 

Before  the  earliest  date  above  mentioned  (1844)  it  was  common  to 
hear  geologists  insisting  on  the  non-existence  of  vertebrate  animals 
of  a  higher  grade  than  fishes  in  the  Coal,  or  in  any  rocks  older  than 
the  Permian.  Even  now,  it  may  be  said,  that  we  have  scarcely 
made  any  progress  in  obtaining  a  knowledge  of  the  terrestrial  fauna 

*  GeoL  Quart.  Journ.  vol.  ix.  p.  58. 
DJ>  3 


406  AIK-BREATHERS   IN   THE    COAL.  [CH.  XXV. 

of  the  coal,  since  the  reptiles  above  enumerated  seem  to  have  been 
all  amphibious.  Negative  evidence  should  have  its  due  weight  in 
paleontological  reasonings  and  speculations,  but  we  are  as  yet  quite 
unable  to  appreciate  its  value.  In  the  United  States,  about  5  mil- 
lions of  tons  of  native  coal  are  annually  extracted  from  the  coal- 
measures,  yet  no  fossil  insect  has  yet  been  met  with  in  the  carboni- 
ferous rocks  of  North  America.  Ought  we  then  to  conclude  that  at 
the  period  of  the  coal  insects  were  unrepresented  in  the  forests  of 
the  Western  World  ?  In  like  manner,  no  land-shell,  no  Helix,  Bu- 
limus,  Pupa,  or  Clausilia,  nor  any  aquatic  pulmoniferous  mollusk, 
such  as  Limneus  or  Planorbis,  is  recorded  to  have  come  from  the 
coal  of  Europe,  worked  for  centuries  before  America  was  discovered, 
and  now  quarried  on  so  enormous  a  scale.  Can  we  infer  that  land- 
shells  were  not  called  into  existence  in  European  latitudes,  until 
after  the  carboniferous  period  ? 

The  theory  of  progressive  development  would  account  readily  for 
the  absence  of  Chelonian  and  Saurian  reptiles,  or  of  Birds  and  Mam- 
mals, from  the  Coal-Measures,  because  the  condition  of  the  planet  is 
supposed  to  have  been  too  immature  and  unsettled  to  permit  creatures 
enjoying  a  higher  development  than  batrachians  to  find  a  fit  domicile 
therein.  But  this  same  theory  leaves  the  scarcity  of  the  inverte- 
brata,  or  the  entire  absence  of  many  important  classes  of  them,  wholly 
unexplained.  When  we  generalize  on  this  subject,  we  must  not 
forget  that  the  eighteen  or  twenty  individual  insects  and  land-shells 
met  with  in  the  coal  (and  most  of  these  very  recently  found),  are 
scarcely  double  the  number  of  the  carboniferous  reptiles  which  have 
been  established  within  the  last  ten  years  on  the  evidence  of  bones 
and  footprints.  Yet  our  opportunities  of  examining  strata  formed 
in  close  connection  with  ancient  land  exceed  in  this  case  all  that  we 
enjoy  in  regard  to  any  other  formations,  whether  primary,  secondary, 
or  tertiary.  We  have  ransacked  hundreds  of  soils  replete  with  the 
fossil  roots  of  trees,  —  have  dug  out  hundreds  of  erect  trunks  and 
stumps,  which  stood  in  the  position  in  which  they  grew,  —  have 
broken  up  myriads  of  cubic  feet  of  fuel  still  retaining  its  vegetable 
structure,  —  and,  after  all,  we  continue  almost  as  much  in  the  dark 
respecting  the  invertebrate  air-breathers  of  this  epoch,  as  if  the 
Coal  had  been  thrown  down  in  mid-ocean.  The  age  of  the  planet, 
or  its  unprepared  state  to  serve  as  a  dwelling  place  for  organized 
beings,  cannot  explain  the  enigma,  because  we  know  that  while  the 
land  supported  a  luxuriant  vegetation,  the  contemporaneous  seas 
swarmed  with  life— with  Articulata,  Mollusca,  Radiata,  and  Fishes. 
We  must,  therefore,  collect  more  facts,  if  we  expect  to  solve  a  pro- 
blem, which,  in  the  present  state  of  science,  cannot  but  excite  our 
wonder ;  and  we  must  remember  how  much  the  conditions  of  this 
problem  have  varied  within  the  last  ten  years.  Meanwhile  let  us  be 
content  to  impute  the  scantiness  of  our  data  chiefly  to  our  want  of 
skill  as  collectors  and  interpreters,  but  partly  also  to  our  ignorance 
of  the  laws  which  govern  the  fossilization  of  land-animals,  whether 
of  high  or  low  degree. 


CH.  XXV.] 


MOUNTAIN   LIMESTONE. 


407 


CARBONIFEROUS   OR  MOUNTAIN  LIMESTONE. 

It  has  been  already  stated  (p.  362.),  that  this  formation  underlies 
the  Coal-Measures  in  the  South  of  England  and  Wales,  whereas  in 
the  North  and  in  Scotland  marine  limestones  alternate  with  Coal- 
Measures,  or  with  shales  and  sandstones,  sometimes  containing  seams 
of  Coal.  In  its  most  calcareous  form  the  Mountain  Limestone  is 
destitute  of  land-plants,  and  is  loaded  with  marine  remains,  —  the 
greater  part  indeed  of  the  rock  being  made  up  bodily  of  corals  and 
crinoids. 

The  Corals  deserve  especial  notice,  as  the  cup-shaped  kinds,  which 
have  the  most  massive  and  stony  skeletons,  display  peculiarities  of 
structure  by  which  they  may  be  distinguished,  as  MM.  Milne 
Edwards  and  Haime  first  pointed  out,  from  all  species  found  in 
strata  newer  than  the  Permian.  There  is,  in  short,  an  ancient  or 
Paleozoic,  and  a  modern  or  Neozoic  type,  if,  by  the  latter  term,  we 
designate  (as  proposed  by  Prof.  E.  Forbes)  all  strata  from  the  tri- 
assic  to  the  most  modern,  inclusive.  The  accompanying  diagrams 
(figs.  514,  515.)  may  illustrate  these  types ;  and,  although  it  may  not 


Fig.  514. 

Paleozoic  type  of  lamelliferous  cup-shaped  Coral.    Order  ZOANTHARIA  ROGOSA,  Milne  Edwards 

and  Jules  Haime. 

a.  Vertical   section    of   Campophyllum  flexuofum    (Cyatho- 
phyllum,  Goldfuss) ;   f  nat.  size :  from  the  Devonian  of 
the  Eifel.    The  lamellce  are  seen  around  the  inside  of  the 
cup;    the    walls    consist    of  cellular   tissue;    and    large 
transverse  plates,  called  tabulce,  divide  the  interior  into 
chambers. 

b.  Arrangement  of  the  lamellfe  in  Polyccelia  ptofunda,  Germar, 

sp. ;  nat.  size:  from  the  Magnesian  Limestone,  Durham. 
This  diagram  shows  the  quadripartite  arrangement  of  the 
lamella?  characteristic  of  paleozoic  corals,  there  being  4 
principal  and  8  intermediate  lamellae,  the  whole  number 
in  this  type  being  always  a  multiple  of  four. 

c.  Stauria  astrceceformis,  Milne  Edwards.    Young  group,  nat. 

size.  Upper  Silurian,  Gothland.  The  lamellae  in  each 
cup  are  divided  by  4  prominent  ridges  into  4  groups. 

Fig.  515. 

Neozoic  type  of  lamelliferous  cup-shaped  Coral.    Order  ZOANTHARIA  APOROSA,  M.  Edwards  and 

J.  Haime. 

a.  Parasmilia  centralis,  Mantell,  sp.  Vertical  section,  nat.  size. 
Upper  Chalk,  Gravesend.  In  this  type  the  lamella:  are  massive, 
and  extend  to  the  axis  of  loose  cellular  tissue,  without  any 
transverse  plates  like  those  in  fig.  514.  a. 

b  Cuathina  Boverbankii,  Edwards  and  Haime.  Transverse  section, 
enlarged  Gault,  Folkstone.  In  this  coral  the  lamella?  are  a 
multiple  of  six.  The  twelve  principal  plates  reach  the  central 
axis  or  columella,  and  between  each  pair  there  are  three  se- 
condary plates,  in  all  forty-eight.  The  short  intermediate  plates 
which  "pr°ceed  from  the  col!amella  are  not  counted.  They  are 

c  FungKat'ellaris^rtk.  Recent:  very  young  state.  Diagram 
'  of  its  six  principal  and  six  intermediate  septa,  magnified.  The 
sextuple  arrangement  is  always  more  manifest  in  the  young 
than  in  the  adult  state. 

always  be  easy  for  any  but  a  practised  naturalist  to  recognise  the 
points  of  structure  here  described,  every  geologist  should  understand 
them,  as  the  reality  of  the  distinction  is  of  no  small  theoretical 

interest. 

DD  4 


408 


FOSSILS    OF    THE 


[Cn.  XXV. 


It  will  be  seen,  that  the  more  ancient  corals  have  what  is  called  a 
quadripartite  arrangement  of  the  stony  plates  or  lamella, —  parts  of 
the  skeleton  which  support  the  organs  of  reproduction.  The  number 
of  these  lamellse  in  the  paleozoic  type  is  4,  8}  16,  &c. ;  while  in  the 
newer  type  the  number  is  always  6,  12,  24,  or  some  other  multiple 
of  six  ;  and  this  holds  good,  whether  they  be  simple  cup-like  forms, 
as  in  figs.  514.  a  and  515.  «,  or  aggregate  clusters  of  cups  as  in 
514.  c. 

It  is  not  enough,  therefore,  to  say  that  the  primary  or  more  an- 
cient corals  are  all  generically  and  specifically  dissimilar  from  the 
secondary,  tertiary,  and  living  corals, —  for,  more  than  this,  they 
belong  to  distinct  Orders,  although  often  so  like  in  outward  form 
as  to  have  been  referred  in  many  cases  to  living  reef-building  genera. 
Hence  we  must  not  too  confidently  draw  conclusions  from  the 
modern  to  the  paleozoic  polyps,  respecting  climate  and  the  temper- 
ature of  the  waters  of  the  primeval  seas,  inasmuch  as  the  two  groups 
of  zoophytes  are  constructed  on  essentially  different  types.  When 
the  great  number  of  the  paleozoic  and  neozoic  species  is  taken  into 
account,  it  is  truly  wonderful  to  find  how  constant  the  rule  above 
explained  holds  good  ;  only  one  exception  having  as  yet  occurred  of 
a  quadripartite  coral  in  a  neozoic  formation  (the  cretaceous),  and  one 
only  of  the  sextuple  class  (a  Fungia  ?)  in  paleozoic  (Silurian)  rocks. 

From  a  great  number  of  lamelliferous  corals  met  with  in  the  Moun- 
tain Limestone,  two  species  have  been  selected,  as  having  a  very 


Fig.  516. 


Fig.  517. 


Lithostrotian  basalt/forme,  Phil.  sp.  (Li- 
ihos  trot  ion  striatum,  Fleming  ;  Astrcea 
basalt>£>rmis,  Conyb.  and  Phill.)  Ken- 
dal ;  Ireland  ;  Russia;  Iowa,  and  west- 
ward of  the  Mississippi,  United  States. 
(D.D.  Owen.) 


Lonsdaleia  floriformis  (Martin,  gp.) 
M.  Edwards.  (Lithostrotionfloriforme, 
Fleming.  Strombodes.) 

a.  Young  specimen,  with  buds  on  the 
disk. 

b.  Part  of  a  full-grown  compound  mass. 

Bristol,  &c. ;  Russia. 


wide  range,  extending  from  the  eastern  borders  of  Russia  to  the 
British  Isles,  and  being  found  almost  everywhere  in  each  country. 

These  fossils,  together  with  numerous  species  of  Zaphrentis,  Am- 
plexus,  Cyathophyllum,  Clisiophyllum,  Syringopora,  a,nd.Michelinea*, 


*  Por  figures  of  these  corals  see  Paleontographical  Society's  Monographs,  1852. 


CH.  XXV.]  MOUNTAIN   LIMESTONE.  409 

form  a  group  widely  different  from  any  that  preceded  or  followed 
them. 

Of  the  Bryozoa,  the  prevailing  forms  are  Fenestella  and  Poly- 
pora,  and  these  often  form  considerable  beds.  Their  net-like  fronds 
are  easily  recognised. 

Crinoidea  are  also  numerous  in  the  Mountain  Limestone.  (See  figs. 
518,  519.) 

Fig.  518.  Fig.  519. 


Ct/athocrim'/es  planux, 
Miller.  Body  and 
arms.  Mountain 
Limestone. 


Cyathocrinus  caryocrinoides,  M'  Coy. 

a.  Surface  of  one  of  the  joints  of  the  stem. 

b.  Pelvis  or  body  ;  called  also  calyx  or  cup. 

c.  One  of  the  pelvic  plates. 


In  the  greater  part  of  them,  the  cup  or  pelvis,  fig.  519.  b,  is 
greatly  developed  in  size  in  proportion  to  the  arms,  although  this  is 
not  the  case  in  fig.  518.  The  genera  Poteriocrinus,  Cyathocrinus, 
Pcntremites,  Actinocrinus,  and  Platycrinus  are  all  of  them  charac- 
teristic of  this  formation.  Other  Echinoderms  are  rare,  a  few  Sea- 
Urchins  only  being  known :  these  have  a  complex  structure,  with 
many  more  plates  on  their  surface  than  are  seen  in  the  modern 
genera  of  the  same  group.  One  genus,  the  Palcechinus  (fig.  520.),  is 
the  analogue  of  the  modern  Echinus.  The  other,  Archceocidaris, 
represents,  in  like  manner,  the  Cidaris  of  the  present  seas. 

Of  Mollusca  the  Brachiopoda  (or  Palliobranchiates)  constitute  the 
larger  part,  and  are  not  only  numerous,  but  often  of  large  size. 
Perhaps  the  most  characteristic  shells  of  the  formation  are  large 
species  of  Productus,  such  as  P.  giganteus,  P.  hemisphcericus,  P  semi- 
reticulatus  (fig.  521.),  and  P.  scabriculus.  Large  plaited  spirifers,  as 


Fig.  521.. 


Fig.  520. 


Pahechinus  gigas,  M'Coy.    Reduced. 
Mountain  Limestone : 
Ireland. 


Productus  semfreficulalus,  Martin,  sp. 
(P.  antiquatus,  Sow.)  Mountain 
Limestone.  England;  Russia;  the 
Andes,  &c. 


410 


FOSSILS    OF    THE 


[Cn.  XXV. 


Spirifer  striatus,  S.  rotundatus,  and  S.  trigonalis  (fig.  522.),  also 
abound ;  and  smooth  species,  such  as  Spirifer  glaber  (fig.  523.)  with 
its  numerous  varieties. 


Fig.  522. 


Fig.  523. 


Spirifer  trigonnlis,  Martin,  sp. 
Moumaiu  Limestone :  Derbyshire,  &c. 


Spirifer  glaber,  Martin,  sp. 
Mountain  Limestone. 


Among  the  palliobranchiate  mollusks  Terebratula  hastata  deserves 
mention,  not  only  for  its  wide  range,  but  because  it  often  retains  the 
pattern  of  the  original  coloured  stripes  which  ornamented  the  living 
shell.  (See  fig.  524.)  These  coloured  bands  are  also  preserved  in 
several  lamellibranchiate  bivalves,  as  in  Aviculopecten  (fig.  525.),  in 
which  dark  stripes  alternate  with  a  light  ground.  In  some  also  of 
the  spiral  univalves,  the  pattern  of  the  original  painting  is  distinctly 
retained,  as  in  the  Pleurotomaria  (fig.  526.),  which  displays  wavy 
blotches,  resembling  the  colouring  in  many  recent  Trochidae. 


Fig.  524. 


Fig.  525. 


Fig.  526. 


Terebratula  hastata, 
Sow., with  radiating 
bands  of  colour. 
Mountain  Lime- 
stone. Derbyshire; 
Ireland;  Russia,  &c. 


Aviculopecten  sublobatus, 
Phill.  Mountain  Lime- 
stone. Derbyshire ; 
Yorkshire. 


Pleurntomaria    carinata.    Sow. 

(P.  flammr'gera,  Phill.) 
Mountain  Limestone.  Derby- 
shire, &c. 


The  mere  fact  that  shells  of  such  high  antiquity  should  have 
preserved  the  patterns  of  their  colouring  is  striking  and  unex- 
pected ;  but  Prof.  E.  Forbes  has  deduced  from  it  an  important  geo- 
logical conclusion.  He  infers  that  the  depth  of  the  primeval  seas 
in  which  the  Mountain  Limestone  was  formed  did  not  exceed  50 
fathoms.  To  this  opinion  he  is  led  by  observing  that  in  the  existing 
seas  the  testacea  which  have  colours  and  well  defined  patterns  rarely 
inhabit  greater  depths  than  50  fathoms  ;  and  the  greater  number 
are  found  where  there  is  most  light  in  very  shallow  water,  not  more 
than  two  fathoms  deep.  There  are  even  examples  in  the  British  seas 
of  testacea  which  are  always  white  or  colourless  when  taken  from 
below  100  fathoms  ;  and  yet  individuals  of  the  same  species,  if  taken 
from  shallower  zones,  are  vividly  striped  or  banded. 


Cn.  XXV.] 


MOUNTAIN   LIMESTONE. 


411 


This  information,  derived  from  the  colour  of  the  shells,  is  the 
more  welcome,  because  the  Radiata,  Articulata,  and  Mollusca  of  the 
Carboniferous  period  belong  almost  entirely  to  genera  no  longer 
found  in  the  living  creation,  and  respecting  the  habits  of  which  we 
can  only  hazard  conjectures. 

Some  few  of  the  carboniferous  mollusca,  such  as  Avicula,  JVucula, 
Solemya,  and  Lithodomus,  belong  no  doubt  to  existing  genera ;  but 
the  majority,  though  often  referred  to  living  types,  such  as  Isocardia, 
Turritella,  and  Buccinum,  belong  really  to  forms  which  appear  to 
have  become  extinct  at  the  close  of  the  paleozoic  epoch.  Euom- 
phalus  is  a  characteristic  univalve  shell  of  this  period.  In  the 
interior  it  is  often  divided  into  chambers  (fig.  527.  d\  the  septa  or 

Fig.  527. 


Fig.  528. 


Ettomphalui  pentagulatus,  Sowerby.    Mountain  Limestone. 
a.  Upper  side ;  b.  lower,  or  umbilical  side ;  c.  view  showing  mouth,  which 
is  less  pentagonal  in  older  individuals ;  d.  view  of  polished  section,  showing 
internal  chambers. 

partitions  not  being  perforated  as  in  foraminiferous  shells,  or  in  those 
having  siphuncles,  like  the  Nautilus.  The  animal  appears  to  have 
retreated  at  different  periods  of  its  growth  from  the  internal  cavity 
previously  formed,  and  to  have  closed  all  com- 
munication with  it  by  a  septum.  The  number  of 
chambers  is  irregular,  and  they  are  generally 
wanting  in  the  innermost  whorl.  The  animal  of 
the  recent  Turritella  communis  partitions  off  in 
like  manner  as  it  advances  in  age  a  part  of  its 
spire,  forming  a  shelly  septum. 

Nearly  20  species  of  the   genus  Bellerophon 
(see  fig.  528.),  a  shell  without  chambers  like  the 
^^^S  Argonaut,  occur  in  the  Mountain  Lime- 
stone.    The  genus  is  not  met  with  in  strata  of 
later   date.      It  is  most  generally  regarded  as  belonging  to  the 


412  FOSSILS   OP   MOUNTAIN   LIMESTONE.  [Cn.  XXV. 

Heteropoda,  and  allied  to  the  Glass- Shell,  Carinaria ;  but  by  some 
few  it  is  thought  to  be  a  simple  form  of  Cephalopod. 

The  carboniferous  Cephalopoda  do  not  depart  so  widely  from  the 
living  type  (the  Nautilus),  as  do  the  more  ancient  Silurian  repre- 
sentatives of  the  same  order ;  yet  they  offer  some  remarkable  forms 
scarcely  known  in  strata  newer  than  the  coal.  Among  these  is 
Orthoceras,  a  siphuncled  and  chambered  shell,  like  a  Nautilus  un- 
coiled and  straightened  (fig.  529.).  Some  species  of  this  genus  are 

Fig.  529. 


Portion  of  Orthoceras  later  ale,  Phillips.    Mountain  Limestone. 

several  feet  long.  The  Goniatite  is  another  genus,  nearly  allied  to 
the  Ammonite^  from  which  it  differs  in  having  the  lobes  of  the  septa 
free  from  lateral  denticulations,  or  crenatures  ;  so  that  the  outline  of 
these  is  continuous  and  uninterrupted. 

The  species  represented  in  fig.  530.  is  found  in  almost  all  localities, 
and  presents  the  zigzag  character  of  the  septal  lobes  in  perfection. 

In  another  species  (fig.  531.),  the  septa  are  but  slightly  waved, 
and  so  approach  nearer  to  the  form  of  those  of  the  Nautilus.  The 


Fig.  530. 


Fig.  531. 


Goruatites  crenistria,  Phill.  Mountain 
Limestone.  N.  America  ;  Britain  ; 
Germany,  &c. 

a.  Lateial  view. 

b.  Front  view,  showing  the  mouth. 


Goniatites  evolutus,  Phillips. 

Mountain  Limestone. 

Yorkshire. 


dorsal  position  of  the  siphuncle,  however,  clearly  distinguishes  the 
Goniatite  from  the  Nautilus,  and  proves  it  to  have  belonged  to  the 
family  of  the  Ammonites,  from  which,  indeed,  some  authors  do  not 
believe  it  to  be  generically  distinct. 

Fossil  fish.  —  The  distribution  of  these  is  singularly  partial;  so 
much  so,  that  M.  de  Koninck  of  Liege,  the  eminent  paleontologist, 
once  stated  to  me  that,  in  making  his  extensive  collection  of  the  fossils 
of  the  Mountain  Limestone  of  Belgium,  he  had  found  no  more  than 
four  or  five  examples  of  the  bones  or  teeth  of  .fishes.  Judging  from 
Belgian  data,  he  might  have  concluded  that  this  class  of  vertebrata 
was  of  extreme  rarity  in  the  carboniferous  seas ;  whereas  the  in- 
vestigation of  other  countries  has  led  to  quite  a  different  result. 


CH.  XXV.]  LOWER   CARBONIFEROUS   STRATA. 


413 


Thus,  near  Clifton,  on  the  Avon,  there  is  a  celebrated  "  bone-bed," 
almost  entirely  made  up  of  ichthyolites ;  and  the  same  may  be  said 
of  the  "fish-beds"  of  Armagh,  in  Ireland.  They  consist  chiefly 
of  the  teeth  of  fishes  of  the  Placoid  order,  nearly  all  of  them 
rolled  as  if  drifted  from  a  distance.  Some  teeth  are  sharp  and 
pointed,  as  in  ordinary  sharks,  of  which  the  genus  Cladodus  affords 
an  illustration  ;  but  the  majority,  as  in  Psammodus  and  Cochliodus, 
are,  like  the  teeth  of  the  Cestracion  of  Port  Jackson  (see  above, 
fig.  288.,  p.  250.),  massive  palatal  teeth  fitted  for  grinding.  (See  figs. 
532,  533.) 


Fig.  532. 


Fig.  533. 


Psammodus  porosus,  Agas.    Bone -bed,  Mountain 
Limestone.    Bristol ;  Armagh. 


Cochliodus  contortiis,  Agas.  Bone-bed, 
Mountain  Limestone.  Bristol ;  Ar- 
magh. 


There  are  upwards  of  70  other  species  of  fish-remains  known  in 
the  Mountain  Limestone  of  the  British  Islands.  The  defensive  fin- 
bones  of  these  creatures  are  not  unfrequent  at  Armagh  and  Bristol  ; 
those  known  as  Oracanthus  are  often  of  a  very  large  size.  Ganoid 
fish,  such  as  ffoloptychius,  also  occur  ;  but  these  are  far  less  nume- 
rous. The  great  Megalichthys  Hibberti  appears  to  range  from  the 
Upper  Coal-measures  to  the  lowest  Carboniferous  strata. 

Foraminifera.  —  This  somewhat  important  group  of  the  lower 
animals,  which  is  represented  so  fully  at  later  epochs  by  the  Num- 
mulites  and  their  numerous  minute  allies,  appears  in  the  Mountain 
Limestone  to  be  restricted  to  a  very  few  species,  the  individuals,  how- 
ever, of  which  are  vastly  numerous.  Textularia,  Nodosaria,  En- 
Fig.  534.  dothyra,  and  Fmulina  (fig.  534.),  have  been  re- 
cognised. The  first  two  genera  are  common  to  this 
and  all  the  after  periods  ;  the  third  has  already 
appeared  in  the  Upper  Silurian,  but  is  not  known 
above  the  Carboniferous  ;  the  fourth  (fig.  534.)  is 
Mountain  Limestone,  peculiar  to  the  Mountain  Limestone,  and  is  charac- 
teristic of  the  formation  in  the  United  States,  Russia,  and  Asia  Minor. 


^ 
Magnified   di 


STRATA   CONTEMPORANEOUS   WITH    THE   MOUNTAIN  LIMESTONE. 

In  countries  where  limestone  does  not  form  the  principal  part 
of  the  Lower  Carboniferous  series,  this  formation  assumes  a  very 
different  character,  as  in  the  Rhenish  Provinces  of  Prussia,  and  in 
the  Hartz.  The  slates  and  sandstones  called  Kiesel-schiefer  and 
Younger  Greywacke  (Jungere  grauwacke)  by  the  Germans,  were 


414      CARBONIFEROUS  LIMESTONE  OF  N.  AMERICA.      [Cn.  XXV. 

ormerly  referred  to  the  Devonian  group,  but  are  now  ascertained  to 
belong  to  the  "  Lower  Carboniferous."  The  prevailing  shell  which 
characterizes  the  carbonaceous  schists  of  this  series,  both  on  the 
Continent  and  in  England,  is  Posidonomya  Becheri  (fig.  535.).  Some 
Fig.  535.  well-known  mountain-limestone  spe- 

cies, such  as  Goniatites  crenistria 
(see  fig.  530.)  and  G.  reticulatus,  also 
occur  in  the  Hartz.  In  the  associated 
sandstones  of  the  same  region,  fossil 
plants,  such  as  Lepidodendron  and 
the  allied  genus  Saginaria,  are  com- 
mon ;  also  Knorria,  Calamites  Suck- 
ovii,  and  C.  transitions  Gopp,  some 
peculiar,  others  specifically  identical 

with  ordinary  coal-measure  fossils.  The  true  geological  position  of 
these  rocks  in  the  Hartz  was  first  determined  by  MM.  Murchison 
and  Sedgwick  in  1840.* 

CARBONIFEROUS   LIMESTONE   IN  NORTH  AMERICA. 

The  coal-measures  of  Nova  Scotia  have  been  described  (p.  379.). 
The  lower  division  contains,  besides  large  stratified  masses  of  gypsum, 
some  bands  of  marine  limestone  almost  entirely  made  up  of  encri- 
nites,  and,  in  some  places,  containing  shells  of  genera  common  to 
the  mountain  limestone  of  Europe. 

In  the  United  States  the  carboniferous  limestone  underlies  the 
productive  coal-measures  ;  and,  although  very  inconspicuous  on  the 
margin  of  the  Alleghany  or  Great  Appalachian  coal-field  in  Penn- 
sylvania, it  expands  in  Virginia  and  Tenessee.  Its  still  greater 
extent  and  importance  in  the  Western  or  Mississippi  coal-fields,  in 
Kentucky,  Indiana,  Iowa,  Missouri,  and  other  western  states,  has 
been  well  shown  by  Dr.  D.  D.  Owen.  In  those  regions  f  it  is  about 
400  feet  thick,  and  abounds,  as  in  Europe,  in  shells  of  the  genera 
Productus  and  Spirifer,  with  Pentremites  and  other  crinoids  and 
corals.  Among  the  latter,  Lithostrotion  basaltiforme  or  striatum 
(fig.  516.  p.  408.),  or  a  closely-allied  species,  is  common. 

*  Trans.  Geol.  Soc.  London,  2nd  f  Owen's  Geol.  Survey  of  Wisconsin, 
series,  vol.  vi.  p.  228.  &c.  1852. 


CH.  XXVI.]  OLD   RED   SANDSTONE.  415 


CHAPTER  XXVI. 

OLD  RED  SANDSTONE,  OR  DEVONIAN  GROUP. 

Old  Red  Sandstone  of  the  Borders  of  Wales — Of  Scotland  arid  the  South  of  Ireland 
— Fossil  reptile  and  foot-tracks  at  Elgin — Fossil  Devonian  plants  at  Kilkenny — 
Ichthyolites  of  Clashbinnie  —  Fossil  fish,  crustaceans,  &c.,  of  Caithness  and 
Forfarshire — Distinct  lithological  type  of  Old  Ked  in  Devon  and  Cornwall — 
Terra  Devonian  —  Organic  remains  of  intermediate  character  between  those  of 
the  Carboniferous  and  Silurian  systems  —  Devonian  series  of  England  and  the 
Continent — Upper  Devonian  rocks  and  fossils  —  Middle  —  Lower — Old  Bed 
Sandstone  of  Kussia  —  Devonian  Strata  of  the  United  States — Coral-reefs  at 
the  Falls  of  the  Ohio. 

IT  has  been  already  shown  in  the  section  (p.  334.),  that  the  car- 
boniferous strata  are  surmounted  by  a  system  called  "The  New 
Red,"  and  underlaid  by  another  termed  the  "  Old  Red  Sandstone."  The 
last-mentioned  group  acquired  this  name  because  in  Herefordshire 
and  Scotland,  where  it  was  originally  studied,  it  consisted  chiefly  of 
red  sandstone,  shale,  and  conglomerate.  It  was  afterwards  termed 
"  Devonian,"  for  reasons  which  will  be  explained  in  the  sequel.  For 
many  years  it  was  regarded  as  very  barren  of  organic  remains ;  and 
such  is  undoubtedly  its  character  over  very  wide  areas  where  cal- 
careous matter  is  wanting,  and  where  its  colour  is  determined  by 
the  red  oxide  of  iron. 

"  Old  Red"  in  Herefordshire,  &c. — In  Herefordshire,  Worcester- 
shire, Shropshire,  and  South  Wales,  this  formation  attains  a  great 
thickness,  sometimes  between  8,000  and  10,000  feet.  In  these  regions, 
it  has  been  subdivided  into 

1st.  Conglomerate,  passing  downwards  into  chocolate-red  and 
green  sandstone  and  marl. 

2nd.  Marl  and  cornstone,  —  red  and  green  argillaceous  spotted 
marls,  with  irregular  courses  of  impure  concretionary  limestone, 
provincially  called  Cornstone,  and  some  beds  of  white  sandstone.  In 
the  cornstones,  and  in  those  flagstones  and  marls  through  which 
calcareous  matter  is  most  diffused,  some  remains  of  fishes  of  the 
genera  Onchus  and  Cephalaspis  occur.  Several  specimens  of  the 
latter  have  been  traced  to  the  lowest  beds  of  the  "  Old  Red,"  in 
May  Hill,  in  Gloucestershire,  by  Sir  R.  Murchison  and  Mr.  Strick- 
land.* 

Old  Red  Sandstone  of  Scotland  and  Ireland.  —  South  of  the 
Grampians,  in  Forfarshire,  Kincardineshire,  and  Fife,  the  Old  Red 
Sandstone  may  be  divided  into  three  groups. 

*  Murchison's  Siluria,  p.  245. 


Fig.  536. 


416         FOSSIL  REPTILE  OF  OLD  RED  SANDSTONE.        [Ca.  XXYI. 

A.  Yellow  sandstone,  with  some  bands  of  white  sandstone. 

B.  Red  shale,  sandstone  with  cornstone,  and  at  the  base  a  con- 

glomerate (Nos.  1,  2,  &  3.  Section,  p.  48.). 

C.  Roofing  and  paving  stone,  highly  micaceous,  and  containing  a 

slight  admixture  of  carbonate  of  lime  (No.  4.,  p.  48.). 
The  upper  member,  or  yellow  sandstone,  A,  is  seen  at  Dura  Den, 
near  Cupar,  in  Fife,  immediately  underlying  the  coal.  It  consists  of 
a  yellow  sandstone  in  which  fish  of  the  genera  Pterichthys  (for  genus 
see  fig.  550.),  Pamphractus,  Glyptopomus,  Holoptychius,  and  others 
abound. 

On  the  south  side  of  the  Moray  Firth,  near  Elgin,  certain  yellow 
and  white  sandstones  were  classed  long  since  by  Professor  Sedgwick 
and  Sir  R.  Murchison  as  the  uppermost  beds  of  the  "  Old  Red ; "  and 
they  are  generally  regarded  as  the  equivalent  of  the  Yellow  Sand- 
stone of  Fife  above  alluded  to.  They  contain  large  rhomboidal 
scales  of  a  fish  called  by  Agassiz  Stagonolepis  Robertsoni,  and  re- 
ferred by  him  to  the  Dipterian  family.  This  family,  observes  Mr. 

Hugh  Miller,  is  emphatically  charac- 
teristic of  the  Old  Red  Sandstone. 
The  scales  of  this  Stagonolepis,  the 
only  parts  of  the  species  yet  known, 
are  so  like  those  of  Glyptopomus  in 
form  and  pattern  that  they  may  pos- 
sibly prove  to  be  referable  to  the 
same  genus.  The  Glyptopomus^  as 
we  have  seen,  is  found  in  the  yellow 
sandstone  of  Dura  Den  in  Fife,  and 
the  genus  has  not  hitherto  been  met 
with  in  any  formation  except  the 
Devonian. 

The  light-coloured  sandstone  of 
Morayshire  passes  down  into  a  con- 
formable series  of  strata,  which  are 
full  of  undoubted  "  Old  Red"  fossils. 
I  have  dwelt  thus  particularly  on  the 
age  of  this  rock,  because  it  has  yielded 
recently  (1851)  the  bones  of  a  reptile, 
the  first  and  only  memorials  of  that 
class  yet  discovered  in  a  stratum  of 
such  high  antiquity.  This  fossil  was 
obtained  by  Mr.  Patrick  Duff,  author 
of  a  "  Sketch  of  the  Geology  of 
Morayshire,"  from  a  quarry  at  Cum- 
mingstone,  near  Elgin.  The  skeleton 
represented  in  the  annexed  figure 
(fig.  536.),  is  41  inches  in  length,  but 
part  of  the  tail  is  concealed  in  the 
rock  ;  and,  if  the  whole  were  visible, 
it  might  be  more  than  6  inches  long. 


Telerpeton  Elginense.    (M^ntell.) 
Natural  size. 

Reptile  in  the  Old  Red  Sandstone,  from 
near  Elgin,  Morayshire. 


CH.  XXVI.]         FOSSIL   FOOTPRINTS   OF   "  OLD    RED.' 


417 


The  matrix  is  a  fine-grained  whitish  sandstone,  with  a  cement  of 
carbonate  of  lime.  Although  almost  all  the  bones  except  those  of 
the  skull  have  decomposed,  their  natural  position  can  still  be  seen. 
Nearly  perfect  casts  of  their  form  were  taken  by  Dr.  Mantell  from 
the  hollow  moulds  which  they  have  left  in  the  rock. 

Slight  indications  are  visible  of  minute  conical  teeth.  Of  ribs  there 
are  twenty-four  pairs,  very  short  and  slender.  The  pelvis  is  placed 
after  the  twenty -fourth  vertebra,  precisely  as  in  the  living  Iguana. 
On  the  whole,  Dr.  Mantell  inferred  that  the  animal  possessed  many 
Lacertian  characters  blended  with  those  of  the  Batrachians.  He 
was  unable  to  decide  whether  it  was  a  small  terrestrial  lizard,  or  a 
freshwater  Batrachian,  resembling  the  Tritons  and  aquatic  Sala- 
manders. 

Although  this  fossil  is  the  most  ancient  quadruped  of  which  any 
osseous  remains  have  yet  been  brought  to  light,  it  seems  not  to  have 
been  the  only  one  then  existing  in  that  region,  for  Captain  Brick- 
enden  observed,  in  1850,  on  a  slab  of  sandstone  from  the  same 
quarry  at  Cummingstone,  a  continuous  series  of  no  less  than  thirty- 
four  footprints  of  a  quadruped.  A  small  part  of  this  track,  the  course 
of  which  is  supposed  to  have  been  from  A  to  B,  is  represented  in  the 
annexed  cut  (fig.  537.).  The  footprints  are  in  pairs,  forming  two 

Fig.  537. 


Scale  one-sixth  the  original  size. 

Part  of  the  trail  of  a  (Chelonian  ?)  quadruped  from  the  Old  Red  Sandstone  of  Cum- 
mingstone,  near  Elgin,  Morayshire.  —  Captain  Brickenden. 

parallel  rows ;  the  hind  foot  being  one  inch  in  diameter  and  larger 
than  the  fore  foot  in  the  proportion  of  4  to  3.  The  stride  must  have 
been  about  4  inches.  The  impressions  resemble  those  left  by  a 
tortoise  walking  on  sand ;  and,  if  this  be  the  true  interpretation  of 
the  trail,  they  are  the  only  indications  as  yet  known  of  a  chelonian 
more  ancient  than  the  trias. 

I  have  already  alluded  (p.  404.)  to.  trails  referred  by  American 
geologists  to  several  species  of  air-breathing  reptiles,  and  discovered 
on  the  eastern  flank  of  the  Alleghany  range,  in  Pennsylvania,  in  a 
red  shale,  so  ancient  that  a  question  has  arisen  whether  the  rock 
should  be  classed  as  the  lowest  member  of  the  carboniferous,  as  Pro- 
fessor H.  D.  Rogers  conceives,  or  as  the  uppermost  Devonian,  as  some 
have  contended  (see  p.  404.).  They  at  least  demonstrate  that  certain 
quadrupeds,  of  larger  size  than  any  of  the  bones  that  have  been 

E  E 


418 


FOSSILS   OF    THE 


[CH.  XXVI. 


ibun  in  carboniferous  rocks,  existed  at  the  time  when  the  ancient 
Red  Shale,  usually  termed  in  the  United  States  "infra-carboni- 
ferous," was  in  the  course  of  deposition. 

In  Ireland  the  upper  beds  of  the  Old  Red,  or  yellow  sandstone  of 
Kilkenny,  contain  fish  of  the  genera  Coccosteus  and  Dendrodus, 
characteristic  forms  of  this  period,  together  with  plants  specifically 
distinct  from  any  known  in  the  coal-measures,  but  referable  to  the 
genera  found  in  them ;  as,  for  example,  Lepidodendron  and  Cyclop- 
teris  (see  figs.  538.  and  539.).  The  stems  of  the  latter  have,  in 
some  specimens,  broad  bases  of  attachment,  and  may  therefore  have 
been  tree-ferns. 


Fig.  538. 


Fig.  539. 


Stem  of  Lepfdodendron,  so  compressed  as 
to  destroy  the  quincunx  arrangement  of 
the  scars.  Upper  Devonian,  Kilkenny. 


Cyclopteris  Hibernica,  Forbes. 
Upper  Devonian,  Kilkenny. 


Fig.  540. 


In  the  same  strata  shells  having  the  form  of  the  genus  Anodon,  and 
which  probably  belonged  to  freshwater  testacea,  occur.  Some  geo- 
logists, it  is  true,  still  doubt  whether  these  beds  ought  not  rather  to 
be  classed  as  the  lowest  beds  of  the  carboniferous  series,  together 
with  the  yellow  sandstone  of  Mr.  Griffiths  (see  p.  362.) ;  but  the  as- 
sociated ichthyolites  and  the  distinct  specific  character  of  the  plants, 
seem  to  favour  the  opinion  above  expressed. 

B.  (Table,  p.  416.) — We  come  next  to  the  middle  division  of  the 
"  Old  Red,"  as  exhibited  south  of  the  Grampians,  and  consisting  of 
—  1st,  red  shale  and  sandstone,  with  some  corn  stone,  occupying  the 
Valley  of  Strathmore,  in  its  course  from  Stonehaven  to  the  Firth  of 

Clyde ;  and,  2ndly,  of  a  conglome- 
rate, seen  both  at  the  foot  of  the 
Grampians,  and  on  the  flanks  of 
the  Sidlaw  Hills,  as  shown  in  the 
section  at  p.  48.,  Nos.  1,  2,  and  3 
In  the  uppermost  part  of  the  divi- 
sion No.  1.,  or  in  the  beds  which, 
in  Fife,  underlie  the  yellow  sand- 
stone, the  scales  of  a  large  ganoid 
fish,  of  the  genus  Holoptychius, 
were  first  observed  by  Dr.  Fleming 
at  Clashbinnie,  near  Perth,  and  an 
entire  specimen,  more  than  2  feet 
in  length,  was  afterwards  found  by 
Mr.  Noble.  Some  of  these  scales 
(see  fig.  540.)  measured  3  inches  in  length,  and  2-|  in  breadth. 


Scale  of  Holoplychius  nobilissimus,  Agas. 
Clashbinnie.    Nat.  size. 


CH.  XXVI.] 


OLD   RED    SANDSTONE. 


419 


C.  (Table,  p.  416.)— The  third  or  lowest  division  south  of  the 
Grampians  consists  of  grey  paving-stone  and  roofing-slate,  with 
associated  red  and  grey  shales ;  these  strata  underlie  a  dense 
mass  of  conglomerate.  In  these  grey  beds  several  remarkable  fish 
have  been  found  of  the  genus  named  by  Agassiz  Cephalaspis,  or 
"  buckler-headed,"  from  the  extraordinary  shield  which  covers  the 
head  (see  fig.  541.),  and  which  has  often  been  mistaken  for  that  of  a 
trilobite,  such  as  Asaphus. 

Fig.  541. 


Cephalaspis  Lyellii,  Agass.    Length  6|  inches. 

From  a  specimen  in  my  collection  found  at  Glammiss,  in  Forfarshire;  see  other  figures, 
Agassiz,  vol.  ii.  tab.  !.«.,  and  1.6. 

a.  One  of  the  peculiar  scales  with  which  the  head  is  covered  when  perfect.     These 

scales  are  generally  removed,  as  in  the  specimen  above  figured. 

b,  c.  Scales  from  different  parts  of  the  body  and  tail. 

In  the  same  rock  at  Carmylie,  in  Forfarshire,  commonly  known  as 
the  Arbroath  paving-stone,  fragments  of  a  huge  crustacean  have  been 
met  with  from  time  to  time.  They  are  called  by  the  Scotch  quarry- 
men  the  "  Seraphim,"  from  the  wing -like  form  and  feather-like  or- 
nament of  the  hinder  part  of  the  head,  the  part  most  usually  met 
with.  Agassiz,  having  previously  referred  some  of  these  fragments 
to  the  class  of  fishes,  was  the  first  to  recognize  their  true  nature,  and 

Fig.  542 


Portions  of  the  Pterygotus  angltcus,  Agassiz. 

1.  Middle  portion  of  the  "  Seraphim  "  or  back  of  the  head,  with  the  scale-like  sculpturing. 

2.  Portion  of  the  dilated  base  of  one  of  the  anterior  feet,  with  its  strong  spines  or  teeth, 

used  as  masticating  organs. 

3.  The  proximal  portion  of  one  of  the  great  anterior  clawg. 

4.  Termination  of  the  same,  with  the  serrated  pincers.    (See  Agass.  Poiss.  Foss.  du  Vieux 

Gr6s  Rouge,  plate  A.) 

1 .  and  2.  are  of  the  natural  size  ;  3  and  4.  are  reduced  one  half. 
E  E   2 


420 


FOSSILS   OF    THE 


[CH.  xxvr. 


Fig.  543. 


in  the  first  plate  of  his  "  Poissons  Fossiles  du  Vieux  Gres  Rouge," 
he  figured  the  portions  on  which  he  founded  his  opinion. 

The  carapace  of  this  huge  crustacean,  which  must  have  rivalled, 
if  not  exceeded  in  size  the  largest  crabs,  is  furnished  at  its  hinder 
part  with  short  prongs,  and  has  two  large  eyes  near  the  middle,  much 
like  those  of  the  Eurypterus  found  in  the  coal  formation  of  Glasgow. 
The  body  consists  of  ten  or  eleven  moveable  rings  (the  exact 

number  is  not  ascertained),  and  was 
terminated  by  an  oval-pointed  tail. 
The  whole  surface  is  covered  by  the 
scale-like  markings  before  mentioned 
as  ornamenting  the  head.  Prof. 
M'Coy,  to  whom  I  owe  these  notes 
on  the  general  structure,  has  kindly 
furnished  me  with  a  restoration  of  the 
entire  animal  (fig.  543.),  which  he 
believes  to  be  closely  allied  to  the 
great  Eurypterus  before  mentioned, 
if  not  of  the  very  same  genus,  and, 
moreover,  of  the  same  family  as  the 
living  King-crab  or  Limulus. 

Sir  R.  Murchison  has  expressed 
some  doubts  *  whether  the  grey  beds 
of  Forfarshire,  containing  the  Ptery- 
gotus,  may  not  be  referable  to  the 
Upper  Silurian  or  Upper  Ludlow 
beds ;  but,  as  they  are  associated  at  Balrudderie  with  numerous 
specimens  of  Cephalaspis)  the  bony  bucklers  or  head-pieces  alone 
being  preserved),  apparently  belonging  to  two  species,  I  think  it 
far  more  probable  that  they  constitute  a  division  of  the  "  Old  Red," 
and  perhaps  not  so  ancient  a  one  as  the  bituminous  schists  (6,  p.  422.) 
in  the  North  of  Scotland. 

In  the  same  grey  paving-stones  and  coarse  roofing  slates  in  which 
the  Cephalaspis  and  Pterygotus  occur,  in  Forfarshire  and  Kincar- 
dineshire,  the  remains  of  grass-like  plants  abound  in  such  numbers 
as  to  be  useful  to  the  geologist  by  enabling  him  to  identify  corres- 
ponding strata  at  distant  points.  Whether  these  be  fucoids,  as  I 
formerly  conjectured,  or  freshwater  plants  of  the  family  Fluviales, 
as  some  botanists  suggest,  cannot  yet  be  determined.  They  are 
often  accompanied  by  fossils,  called  "  berries "  by  the  quarrymen, 
and  which  are  not  unlike  the  form  which  a  compressed  blackberry 
or  raspberry  might  assume  (see  figs.  544.  and  545.).  Some  of  these 
were  first  observed  in  the  year  1828,  in  grey  sandstone  of  the  same 
age  as  that  of  Forfarshire,  at  Parkhill  near  Newburgh,  in  the  north 
of  Fife,  by  Dr.  Fleming.  I  afterwards  found  them  on  the  north  side 
of  IStrathmore,  in  the  vertical  shale  beneath  the  conglomerate,  and 
in  the  same  beds  in  the  Sidlaw  Hills,  at  all  the  points  where  fig.  4. 
is  introduced  in  the  section,  p.  48. 

*  Siluria,  p.  247. 


Pterygotus  problem  aliens,  Agassiz. 
Restoration  by  Professor  M'Coy. 


Cn.  XXVI.]  OLD    KED   SANDSTONE. 

Fig.  544.  Fig.  545. 


421 


Parka  decipiens,  Fleming. 
In  sandstone  of  lower  beds 

of  Old  Red,  Ley's  Mill, 

Forfarshire. 


Parka  decipiens,  Fleming. 
In  shale  of  lower  beds  of  Old  Red,  Fife. 


Fig.  546. 


Dr.  Fleming  has  compared  these  fossils  to  the  panicles  of  a  Juncus, 
or  the  catkins  of  Sparganium,  or  some  allied  plant,  and  he  was  con- 
firmed in  this  opinion  by  finding  a  specimen  at  Balrudderie,  showing 
the  under  surface  smoother  than  the  upper,  and  displaying  what  may 
be  the  place  of  attachment  of  a  stalk.  I  have  met  with  some  speci- 
mens in  Forfarshire  imbedded  in  sandstone,  and  not  associated  with 
the  leaves  of  plants  (see  fig.  544.),  which  bore  a  considerable  resem- 
blance to  the  spawn  of  a  recent  Natica  (fig.  546.),  in 
which  the  eggs  are  arranged  in  a  thin  layer  of  sand, 
and  seem  to  have  acquired  a  polygonal  form  by  press- 
ing against  each  other;  but,  as  no  gasteropodous 
shells  have  been  detected  in  the  same  formation,  the 
Parka  has  probably  no  connection  with  this  class  of 

Fragment  of  spawn  Organisms. 

ot  British  species      The  jate  Dr.  Mantell  was  so  much  struck  with  the 

of  Nattca.  -  . 

resemblance  of  one  of  my  specimens  (see  fig.  547.)  to 
a  small  bundle  of  the  dried-up  eggs  of  the  Icommon  English  frog, 
which  he  had  obtained  in  a  black  and  carbonaceous  state  (see  fig. 
548.)  from  the  mud  of  a  pond  near  London,  that  he  suggested  a 


Fig.  547. 


Fig.  548. 


Fossil.  — Old  Red. 


Recent. 


Fig.  54D. 


Fisr.  547.  Slab  of  Old  Red  Sandstone,-) 
Forfarshire,  with  bodies  like  the  ova  |  ~ 
of  Batrachians. 

a.  Ova  ?  in  a  carbonized  state. 

b.  Egg  cells?,  the  ova  shed. 

Fig.  548.   Eggs  of  the  common  frog,") 
liana   temporaria,  in  a  carbonized 
state,  from  a  dried-up  pond  in  Clap- 1  *; 
ham  Common. 

a.  The  ova. 

b.  A  transverse  section  of  the  mass  j  & 

exhibiting  the  form  of  the  egg- 


Fig.  549.  Sh*le  of  Old  Red  Sandstone,  or 
Devonian,  Forfarshire,  with  impression 
of  plants  and  eggs  of  Batrachians  ? 

a.  Two  pair  of  ova?  resembling  tb^e  of 

large  Salamanders  or  Triton^-  on 
the  same  leaf. 

b.  b.  Detached  ova  ? 

c.  Egg-cells  (?)  of  frogs  or  llanina 


EE  8 


422  OLD   KED    OF    NORTH    OF    SCOTLAND.       [Cn.  XXVI. 

batrachian  origin  for  the  fossil ;  and  Mr.  Newport  concurred  in  the 
idea,  adding  that  other  larger  and  more  circular  fossils  (fig.  549.), 
which  I  procured  from  shale  in  the  same  "Old  Red,"  occurring 
singly  or  in  pairs,  and  attached  to  the  leaves  of  plants,  might 
possibly  be  the  ova  of  some  gigantic  triton  or  salamander. 

The  general  absence  of  reptilian  remains  from  strata  of  the  Devo- 
nian period  will  weigh  strongly  with  many  geologists  against  such 
conjectures. 

"  Old  Red"  in  the  North  of  Scotland. —  The  whole  of  the  northern 
part  of  Scotland,  from  Cape  Wrath  to  the  southern  flank  of  the 
Grampians,  has  been  well  described  by  Mr.  Hugh  Miller  as  consist- 
ing of  a  nucleus  of  granite,  gneiss,  and  other  hypogene  rocks,  which 
seem  as  if  set  in  a  sandstone  frame.*  The  beds  of  the  Old  Red 
Sandstone  constituting  this  frame  may  once  perhaps  have  extended 
continuously  over  the  entire  Grampians  before  the  upheaval  of  that 
mountain  range  ;  for  one  band  of  the  sandstone  follows  the  course  of 
the  Moray  Frith  far  into  the  interior  of  the  great  Caledonian  valley, 
and  detached  hills  and  island-like  patches  occur  in  several  parts  of 
the  interior,  capping  some  of  the  higher  summits  in  Sutherlandshire, 
and  appearing  in  Morayshire  like  oases  among  the  granite  rocks  of 
Strathspey.  On  the  western  coast  of  Ross-shire,  the  Old  Red  forms 
those  three  immense  insulated  hills  before  described  (p.  67.),  where 
beds  of  horizontal  sandstone,  3000  feet  high,  rest  unconformably  on 
a  base  of  gneiss,  attesting  the  vast  denudation  which  has  taken  place. 

As  the  mineral  character  of  the  "  Old  Red"  north  of  the  Grampians 
differs  considerably  from  that  of  the  south,  especially  in  the  middle 
and  lower  divisions,  I  shall  now  allude  to  it  separately.  The  upper 
portion,  consisting  of  light-coloured  sandstones,  and  containing  the 
Telerpeton  of  Elgin,  has  been  already  classed,  A.,  p.  416.,  as  the 
equivalent  of  the  yellow  sandstone  of  Fife.  That  upper  member 
passes  downwards  into  red  and  variegated  sandstone  and  conglome- 
rate, which  may  correspond  with  the  beds  called  B.,  in  the  same 
section  at  p.  416.  To  the  above  succeeds,  in  the  descending  order, 
"  the  middle  formation"  of  Mr.  Hugh  Miller,  composed  of  thin,  fissile, 
grey  sandstone,  in  which,  in  Morayshire,  Dr.  Malcolmson  found  a  spe- 
cies of  Cephalaspis ;  but  whether  these  beds  are  of  the  age  of  the 
paving-stone  of  Arbroath  (C.,  Table,  p.  416.)  is  as  yet  uncertain. 

Next  below  is  the  "inferior  division"  of  Hugh  Miller,  com- 
prising :  — 

a.  Red  and  variegated  sandstones. 

b.  Bituminous  schists. 

c.  Coarse  sandstone. 

d.  Great  conglomerate. 

In  the  schists  6,  a  great  variety  of  fish  are  met  with  in  the  coun- 
ties of  Banff,  Nairn,  Moray,  Cromarty,  and  Caithness,  and  also  in 
OrMley,  belonging  to  the  genera  Pterichthys  (fig.  550.),  Coccosteus, 
Diplopterus,  Dipterus,  Cheiracanthus,  Asterolepis,  and  others  de- 
scribed by  Agassiz. 

*  "  Old  Eed  Sandstone,"  1841. 


CH.  XXVI.]  T,ERM    "  DEVONIAN/'  423 

Five  species  of  Pterichthys  have  been  found  in  this  lowest  di- 
vision of  the  Old  Red.  The 
wing-like  appendages,  whence 
the  genus  is  named,  were  first 
supposed  by  Mr.  Miller  to  be 
paddles,  like  those  of  the 
turtle;  but  Agassiz  regards 
them  as  weapons  of  defence, 
like  the  occipital  spines  of  the 
River  Bull-head  (  Cottus  gobio, 
Linn.) ;  and  considers  the  tail 
to  have  been  the  only  organ  of 
motion.  The  genera  Dipterus 
and  Diplopterus  are  so  named, 
because  their  two  dorsal  fins 
are  so  placed  as  to  front  the 
anal  and  ventral  fins,  so  as  to 
appear  like  two  pair  of  wings. 
They  have  bony  enamelled 
scales. 

The  Aster  olepis  was  a  ganoid  fish  of  gigantic  dimensions.  A.  As- 
musti,  Eichwald,  the  species  characteristic  of  the  Old  Red  Sandstone 
of  Russia,  as  well  as  that  of  Scotland,  attained  the  length  of  between 
20  and  30  feet.  It  was  clothed  with  strong  bony  armour,  embossed 
with  star-like  tubercles,  but  it  had  only  a  cartilaginous  skeleton. 
The  mouth  was  furnished  with  two  rows  of  teeth,  the  outer  ones 
small  and  fish-like,  the  inner  larger  and  with  a  reptilian  character. f 
The  Aster  olepis  occurs  also  in  the  Devonian  rocks  of  North  America, 
in  the  lower  division  of  the  Old  Red.  Coniferous  wood,  with  struc- 
ture showing  medullary  rays,  has  likewise  been  detected  in  the  lower 
division  by  Hugh  Miller  J,  who  has  pointedly  dwelt  on  the  import- 
ance of  the  fact,  as  the  oldest  example  yet  known  of  so  highly  or- 
ganized a  plant  occurring  in  a  rock  of  such  antiquity. 

South  Devon  and  Cornwall. —  Term  Devonian. — A  great  step 
was  made  in  the  classification  of  the  slaty  and  calciferous  strata  of 
South  Devon  and  Cornwall  in  1837,  when  a  large  portion  of  the 
beds,  previously  referred  to  the  "transition"  or  Silurian  series, 
were  found  to  belong  in  reality  to  the  period  of  the  Old  Red  Sand- 
stone. For  this  reform  we  are  indebted  to  the  labours  of  Professor 
Sedgwick  and  Sir  R.  Murchison,  assisted  by  a  suggestion  of  Mr. 
Lonsdale,  who,  in  1837,  after  examining  the  South  Devonshire 
fossils,  perceived  that  some  of  them  agreed  with  those  of  the  Carbon- 
iferous group,  others  with  those  of  the  Silurian,  while  many  could 
not  be  assigned  to  either  system,  the  whole  taken  together  exhibiting 
a  peculiar  and  intermediate  character.  But  these  paleontological 
observations  alone  would  not  have  enabled  us  to  assign,  with  accu- 

*  Old  Red  Sandstone.   Plate  1.  fig.  1.         f  Footprints  of  the  Creator,  by  Hugh 
Mr.  Miller's  description  of  the  fish  is     Miller, 
most  graphic  and  correct.  J  Footprints,  p.  199. 

E  E  4 


424  DEVONIAN    SERIES.  [Cn.  XXVI. 

racy,  the  true  place  in  the  geological  series  of  these  slate-rocks  and 
limestones  of  South  Devon,  had  not  Messrs.  Sedgwick  and  Murchison, 
in  1836  and  1837,  discovered  that  the  culmiferous  or  anthracitic 
shales  of  North  Devon  belonged  to  the  Coal,  and  not,  as  preceding 
observers  had  imagined,  to  the  "  transition  "  period. 

As  the  strata  of  South  Devon  here  alluded  to  are  far  richer  in 
organic  remains  than  the  red  sandstones  of  contemporaneous  date  in 
Herefordshire  and  Scotland,  the  new  name  of  the  "  Devonian  system  " 
was  proposed  as  a  substitute  for  that  of  Old  Red  Sandstone. 

The  link  supplied  by  the  whole  assemblage  of  imbedded  fossils, 
connecting  as  it  does  the  paleontology  of  the  Silurian  and  Carbon- 
iferous groups,  is  one  of  the  highest  interest,  and  equally  striking 
whether  we  regard  the  genera  of  the  corals  or  of  the  shells.  The 
species  are  mostly  distinct  except  in  the  upper  group. 

The  rocks  of  this  group  in  South  Devon  consist,  in  great  part,  of 
green  chloritic  slates,  alternating  with  hard  quartzose  slates  and 
sandstones.  Here  and  there  calcareous  slates  are  interstratified  with 
blue  crystalline  limestone,  and  in  some  divisions  conglomerates, 
passing  into  red  sandstone.  But  the  whole  series  is  much  altered 
and  disturbed  by  the  intrusion  of  the  granite  of  Dartmoor  and  other 
igneous  rocks. 

In  North  Devon,  on  the  contrary,  the  Devonian  group  has  been 
less  changed,  and  its  relations  to  the  overlying  carboniferous  rocks 
or  "  Culm  Measures  "  are  clearly  seen.  The  following  sequence  is 
exhibited  in  the  coast  section  on  the  Bristol  Channel  between 
Barnstaple  and  the  North  Foreland.* 

Devonian  Series  in  North  Devon. 

{fa.  Calcareous  brown  slates  ;  with  fossils,  many  of  them  common  to 
1.  <          the  Carboniferous  group.     (Barnstaple,  Pilton,  &c.) 
\^b.  Brown  and  yellow  sandstone,  with  shells  and  land- plants  —  Stig- 
maria,  Knorria,  and  others.     (Baggy  Point,  Marwood,  &c.) 
"2.  Hard  grey  and  reddish  sandstones  and  micaceous  flags,  without 
fossils,  resting  on  soft  greenish  schists  of  considerable  thickness. 
M'ddl  «J          (Morte  Bay,  Bull  Point,  &c.) 

e~^  3.  Calcareous  slates,  with  eight  or  nine  courses  of  limestone,  full  of 
corals  and  shells  like  those  of  the  Plymouth  limestone.     (Combe 
Martin,  Ilfracombe  Harbour,  &c.) 
j  4.  Hard,  greenish,  red,  and  purple  sandstones  :  with  occasional  fossils, 
T  j  Spirifers,  &c.     (Linton,  North  Foreland,  &c.) 

r  j  5.  Soft  chloritous  slates,  with  some  sandstones;    Orthis,  Spirifer,   and 
some  Corals.     (Valley  of  Rocks,  Lynmouth,  &c.) 

The  successive  beds  of  this  section  have  been  compared  with 
those  of  South  Devon  and  Cornwall  both  by  the  authors  of  the 
"Devonian"  system  and  by  other  observers.  And  Prof.  Sedgwick 
has  again  lately  brought  them  into  closer  comparison.f  Other 
geologists  at  home  and  abroad  have  successively  identified  them 
with  the  Devonian  series  in  France,  Belgium,  the  Rhenish  Provinces, 

*  Sedgwick  and  Murchison,  Trans.  Cornwall,  pi  3.  Murchison's  Siluria, 
Geol.  Soc.,  New  Series,  vol.  v.  p.  644.  p.  256. 

De  la  Beche,  Geol.  Report,  Devon  and          j  Quart.  Journ.  Geol.  Soc.,  vol.  viii. 

p.  1.,  et  $eq. 


UPPER   AND    MIDDLE   DEVONIAN. 


425 


Fig.  551. 


CH.  XXVI.] 

Central  Germany,  and  America.*    I  shall  proceed  first  to  treat  of 
the  main  divisions  which  have  been  established  in  Europe. 

Upper  Devonian  Rocks. 

The  slates  and  sandstones  of  Barnstaple  (No.  1.  #,  b.  of  the 
preceding  section)  are  represented  in  Cornwall  by  the  limestones 
and  slates  of  Petherwyn,  which  rise  in  like  manner  from  under  the 

Culm  Measures,  constituting  the 
Petherwyn  group  of  Prof.  Sedg- 
wick.  These  beds  contain  the 
very  common  Spirifer  disjunctus, 
Sow.  (S.  Verneuilii,  Murch.),  (see 
fig.  551.),  a  species  distributed 
over  the  whole  of  Europe,  and 
found  even  in  Asia  Minor  and 
China.  Among  many  other  fossils 
the  Clymenia  linearis  (fig.  552.)  and  the  minute  crustacean  Cypri- 
dina  serrato-striata  (fig.  553.)  are  so  characteristic  of  these  upper 


Spirifer  disjunctus,  Sow.    Syn.  Sp.  Verneuilii, 

Murch. 
Upper  Devonian,  Boulogne. 


Fig.  552. 


Fig.  553. 


Ci/prt'riina  serrato-striata,  Sandberger. 
'  Weilburg,  &c. ;  Nassau  ;  Saxony ; 
Belgium. 


Clymenia  lineart's.  Minister. 
Petherwyn,  Cornwall;  Elbersreuth,  Bavaria. 

beds  in  Belgium,  the  Rhenish  Provinces,  the  Hartz,  Saxony,  and 
Silesia,  that  strata  of  this  division  in  Germany  are  distinguished  by 
the  names  of  "  Clymenien-Kalk,"  and  "  Cypridinen-schiefer."  f 

With  these  are  many  Goniatites  (G.  subsulcatus,  Munster,  and 
other  species)  both  in  England  and  on  the  continent.  In  Germany 
they  are  usually  confined  to  distinct  beds,  as  at  Oberscheld,  also  at 
Couvin  in  Belgium,  &c.  Trilobites  are  not  unfrequent  in  Cornwall 
and  North  Devon ;  they  are  chiefly  restricted  to  species  of  Phacops 
(for  genus,  see  fig.  585.) ;  but  in  the  upper  Devonian  limestones  of 
the  Fichtelgebirge,  as  at  Elbersreuth  in  Bavaria,  there  are  numerous 
genera  and  species  which  never  rise  higher  in  the  series  or  appear 
in  any  portion  of  the  carboniferous  limestone. 

Middle  Devonian. 

The  unfossiliferous  series  (No.  2.,  p.  424.)  of  North  Devon,  and  the 
calcareous  beds  of  Ilfracombe  (3.),  correspond  to  the  Dartmouth  and 


*  See  Dr.  Fred.  Sandberger  on  the 
Devonian  rocks  of  Nassau  (Geol.  Ver- 
halt.  Nassati)  ;  Fred.  Roemer,  on  the 
Hartz  Devonian  Rocks,  in  Dunker  and 


Von    Meyer's   Palacontographica,    3rd 
vol.  pt.  1. 

t  See  Murchison's  Siluria,  chaps,  x., 
xiv.,  and  xv. 


426 


FOSSILS   OF    THE 


[OH.  XXVJ. 


Plymouth  groups  of  Prof.  Sedgwick's  South  Devon  series,  and  are 
the  most  typical  portion  of  the  Devonian  system.  They  include  the 
great  limestones  of  Plymouth  and  Torbay,  replete  with  shells, 
trilobites,  and  corals.  A  thick  accumulation  of  slate  and  schist,  full  of 
the  same  fossils,  occupies  nearly  all  the  southern  portion  of  Devon- 
shire and  a  large  part  of  Cornwall.  Among  the  corals  we  find  the 
genera  Favosites,  Heliolites^  and  Cyathophyllum,  the  last  genus 
equally  abundant  in  the  Silurian  and  Carboniferous  systems,  the  two 
former  so  frequent  in  Silurian  rocks.  Some  few  even  of  the  species 
are  common  to  the  Devonian  and  Silurian  groups,  as,  for  example, 
Favosites  polymorpha  (fig.  554.),  one  of  the  commonest  of  all  the 
Devonshire  fossils.  The  Cyathophyllum  ccBSpitosum  (fig.  555.)  and 


Fig.  555. 


Fig.  554. 


Favosites  polymorpha,  Goldf.     S.  Devon,  from  a  polished 

specimen. 
a.  Portion  of  the  same  magnified,  to  show  the  pores. 


a.  Cyathophyllum  caspitosum, 

Goldf.  Plymouth. 
6.  a  terminal  star. 
c.  vertical  section,    exhibiting 

transverse  plates,  and  part  of 

another  branch. 


Heliolites  pyriformis  (fig.  556.)  are  peculiarly  characteristic ;  as  is 
another  very  common  species,  the  Aulopora  serpens  (fig.  557.), 
which  creeps  over  corals  and  shells  in  its  young  state,  as  here 


Fig.  557. 


Fig.  556. 


Heliolites  porosa,  Goldf.,  sp.  Forties  pyriformis, 

Lonsd. 

a.  portion  of  the  same  magnified.    Middle  De- 
vonian, Torquay  ;  Plymouth  ;  Eifel. 


Aulopora  serpens,  Goldf. 

(The  yoxmg  basal  portion  of  a  Syringopora, 

Milne  Edw.  and  Haime.) 


figured,  but  afterwards  grows  upwards  and  becomes  a  cluster  of 
tubes  connected  by  minute  processes.  In  this  state  it  has  been 
supposed  to  be  a  distinct  coral,  and  has  been  called  Syringopora. 


CH.  XXVI.]  MIDDLE    DEVONIAN.  427 

With  the  above  are  found  many  stone-lilies  or  crinoids,  some  of 
them,  such  as  Cupressocrinites,  of  forms  generically  distinct  from 
those  of  the  Carboniferous  Limestone.  The  mollusks  also  are  no 
less  characteristic,  among  which  the  genus  Stringocephalus  (fig.  558.) 


Stringocephalus  Burtini,  Defr.    (Terebralula  porrecta,  Sow.)    Eifel;  also  South  Devon. 
a.  valves  united.  b.  side  view  of  same. 

c.  interior  of  larger  valvo.  lowing  thick  partition,  and  part  of  a  large  process  which 
projects  from  its  upper  end  quite  across  the  shell. 

may  be  mentioned  as  exclusively  Devonian.  Many  other  Brachiopod 
shells,  of  the  genus  Spirifer,  &c.,  abounded,  and  among  them  the 
Atrypa  reticularis,  Linn.  sp.  (fig.  575.  p.  438.),  which  seems  to  have 
been  a  cosmopolite  species  occurring  in  Devonian  strata  from 
America  to  Asia  Minor,  and  which,  as  we  shall  hereafter  see 
(p.  437.),  lived  also  in  the  Silurian  seas.  Among  the  peculiar 
lamellibranchiate  bivalves  common  to  the  Plymouth  limestone  of 
Devonshire  and  the  Continent,  we  find  the  Megalodon  (fig.  559.), 
together  with  many  spiral  univalves,  such  as  Murchisonia,  Euom- 
phalus,  and  Macrocheilus ;  and  Pteropods  such  as  Conularia  (fig.  560.). 


Fig.  -560. 


Fig.  559. 


Megalodon  cucullatus,  Sow.    Eifel ;  also  Bradley,  S.  Devon.  Conularia  ornata,  D'Arch.  etDe 

a.  the  valves  united.  Vern. 

b.  Interior  of  valve,  showing  the  large  cardinal  tooth.  (Geol.  Trans.  2d  s.  vol.vi.  pi.  29.) 

Refrath,  near  Cologne. 

The  cephalopoda,  such  as  Cyrtoceras,  Gyroceras,  and  others,  are 
nearly  all  of  genera  distinct  from  those  prevailing  in  the  Upper 
Devonian  Limestone,  or  Clymenien-kalk  of  the  Germans  already 
mentioned  (p.  425.).  Although  but  few  species  of  Trilobites  occur, 
the  characteristic  Brontes  flabellifer  (fig.  561.  p.  428.)  is  far  from  rare, 
and  all  collectors  are  familiar  with  its  fan-like  tail.  The  head  is 
seldom  found  perfect;  a  restoration  of  it  has  been  attempted  by 
Mr.  Salter  (fig.  562.) 

In  this  same  formation,  comprising  in  it  the  "  Stringocephalus 


428 


LOWEK    DEVONIAN. 


[Cn.  XXVI, 


Fig.  561. 


Fig.  562. 


Calceola  sandalina,  Lam.    Eifel ;  also  South  Devon, 
a.  ventral  valve.      6.  inner  side  of  dorsal  valve. 


Restored  outline  of  head  of  Brontes 
fiabellifer. 


Brontes ftabellifer,  Goldf.    Eifel;  also  S.  Devon. 

limestone,"  or  "  Eifel  Limestone  "  of  Germany,  several  remains  of 
Coccosteus  and  other  ichthyolites  have  been  detected,  and  they  serve, 
as  Sir  R.  Murchison  observes  (Siluria,  p.  371.),  to  identify  the  rock 

with  the  Old  Red  Sandstone 
of  Britain  and  Russia. 

Beneath  the  great  Eifel 
Limestone  (the  principal  type 
of  "the  Devonian"  on  the 
Continent),  lie  certain  schists 
called  by  German  writers 
"  Calceola-schiefer  "  because 
they  contain  in  abundance  a 
fossil  brachiopod  of  very  curious  structure,  Calceola  sandalina 
(fig.  563.). 

Lower  Devonian. 

Beneath  the  Middle  Devonian  limestones  and  schists  already 
enumerated,  a  series  of  slaty  beds  and  quartzose  sandstones,  the 
latter  constituting  the  "  Older  Rhenish  Greywacke  "  of  Roemer,  and 
the  "  Spirifer  sandstone "  of  Sandberger,  are  exhibited  between 
Coblentz  and  Caub.*  A  portion  of  these  rocks  on  the  Rhine  and  in 
some  of  the  adjacent  countries  were  regarded  as  "Upper  Silurian" 
by  Prof.  Sedgwick  and  Sir  R.  Murchison  in  1839,  but  their  true 
age  has  since  been  determined.  Their  equivalents  are  found  in 
England  in  the  sandstones  and  slates  of  the  North  Foreland  and 
Linton  in  Devon  (Nos.  4.  and  5.  of  the  section,  p.  424.),  and, 
according  to  Mr.  Salter,  in  the  sandstone  of  Torbay  in  South 
Devon,  where  many  of  the  characteristic  Rhenish  fossils  are  met 

with.  The  broad-winged 
Spirifers  which  distin- 
guish the  "  Spirifer-sand- 
stein  "  of  Germany  have 
their  representatives  in 
the  Devonian  strata  of 
N.  America  (see  fig.  564.). 


Fig.  564. 


Spirifer  mucronatus,  Hall.    Devonian  of  Pennsylvania. 


*  Murchiscm's  Siluria,,  p.  368. 


DEVONIAN   OF   RUSSIA. 


429 


CH.  XXV I.] 

Among  the  Trilobites  of  this  era  a  large  species  of  Homalonotus 
(fig.  565.)  is  conspicuous.  The  genus  is  still  better  known  as  a 
Silurian  form,  but  the  spinose  species  appear  to  belong  exclusively 
to  the  "  Lower  Devonian." 

With  the  above  are  associated  many  species  of  Brachiopods,  such 
as  Qrthis,  Lept&na,  and  Chonetes,  and  some  LamelUbranchiata,  such 
as  Pterinea ;  also  the  very  remarkable  fossil  coral,  called  Pleuro- 
dictyum  problematicum  (fig.  566.) 


Fig.  565. 


Fig.  566. 


Pleurodictyum  problematicum,  Goldfuss.  Lower 
Devonian  ;  Dietz,  Nassau,  &c. 

Obs.  Attached  to  a  worm-lika  body  (Serpula). 
The  specimen  is  a  cast  in  sandstone,  the  thin 
expanded  base  of  the  coral  being  removed,  and 
exposing  the  large  polygonal  cells ;  the  walls  of 
these  cells  are  perforated,  and  the  casts  of  these 
perforations  produce  the  chain-like  rows  of  dots 
between  the  cells. 


Homalonotus  armatns,  Burmeister.    Lower 

Devonian  ;  Daun,  in  the  Eifel. 
Obs.  The  two  rows  of  spines  down  the  body 
give  an  appearance  of  more  distinct  triloba- 
tion  than  really  occurs  in  this  or  most  other 
species  of  the  genus. 

Devonian  of  Russia.  —  The  Devonian  strata  of  Russia  extend, 
according  to  Sir  R.  Murchison,  over  a  region  more  spacious  than 
the  British  Isles ;  and  it  is  remarkable  that,  where  they  consist  of 
sandstone  like  the  "Old  Red"  of  Scotland  and  Central  England, 
they  are  tenanted  by  fossil  fishes  often  of  the  same  species  and  still 
oftener  of  the  same  genera  as  the  British,  whereas  when  they  consist 
of  limestone  they  contain  shells  similar  to  those  of-  Devonshire,  thus 
confirming,  as  Sir  Roderick  observes,  the  contemporaneous  origin 
previously  assigned  to  formations  exhibiting  two  very  distinct 
mineral  types  in  different  parts  of  Britain.*  The  calcareous  and  the 
arenaceous  rocks  of  Russia  above  alluded  to  alternate  in  such  a 
manner  as  to  leave  no  doubt  of  their  having  been  deposited  at  the 
same  period.  Among  the  fish  common  to  the  Russian  and  the  British 
strata  are  Asterolepis  Asmusii  before  mentioned ;  a  smaller  species, 
A.  minor,  Ag. ;  Holoptychius  nobilissimus  (p.  418.);  Dendrodus 
strigatus,  Owen ;  Pterichthys  major,  Ag. ;  and  many  others.  But 
some  of  the  most  marked  of  the  Scottish  genera,  such  as  Cephalaspis, 
Coccosteus,  Diplacanthus,  Cheiracanthus,  &c.,  have  not  yet  been 
found  in  Russia,  owing  perhaps  to  the  present  imperfect  state  of  our 
researches,  or  possibly  to  geographical  causes  limiting  the  range  of 

*  Siluria,  p.  329. 


430  DEVONIAN  STRATA  [On.  XXVI. 

the  extinct  species.  On  the  whole,  no  less  than  forty  species  of 
placoid  and  ganoid  fish  have  been  already  collected  in  Russia,  some 
of  the  placoids  being  of  enomous  size,  as  before  stated,  p.  423. 


Devonian  Strata  in  the  United  States. 

In  no  country  hitherto  explored  is  there  so  complete  a  series  of 
strata  intervening  between  the  Carboniferous  and  Silurian  as  in  the 
United  States.  This  intermediate  or  Devonian  group  was  first 
studied  in  all  its  details,  and  with  due  attention  to  its  fossil  remains, 
by  the  Government  Surveyors  of  New  York.  In  its  geographical 
extent,  that  State,  taken  singly,  is  about  equal  in  size  to  Great 
Britain ;  and  the  geologist  has  the  advantage  of  finding  the 
Devonian  rocks  there  in  a  nearly  horizontal  and  undisturbed  con- 
dition, so  that  the  relative  position  of  each  formation  can  be  ascer- 
tained with  certainty. 

Subdivisions  of  the  Neiv  York  Devonian  Strata,  in  the  Reports  of 
the  Government  Surveyors. 

Names  of  Groups.  Thickness  in  Feet. 

1.  Catskill  group  or  Old  Red  Sandstone       -  2000 

2.  Chemung  group  -  ...     1500 

3.  Portage   1  ^  - 

4.  GenesseeJ 

5.  Tully       -  -  -  -  *•*»;-.     .?-..-        -         15 

6.  Hamilton  -  «»--'*        -     1000 

7.  Marcellus  -  -  -  -    '        -  50 

8.  Corniferous\ 

9.  Onondaga  J 

10.  Schoharie  1 

11.  Cauda-Galli  grit  J 

12.  Oriskany  sandstone  -v  -  «-  .,          5  to  30 

These  subdivisions  are  of  very  unequal  value,  whether  we  regard 
the  thickness  of  the  beds  or  the  distinctness  of  their  fossils ;  but 
they  have  each  some  mineral  or  organic  character  to  distinguish 
them  from  the  rest.  Moreover,  it  has  been  found,  on  comparing  the 
geology  of  other  North  American  States  with  the  New  York 
standard,  that  some  of  the  above-mentioned  groups,  such  as  Nos.  2. 
and  3.,  which  are  respectively  1500  and  1000  ft.  thick  in  New  York, 
are  very  local  and  thin  out  when  followed  into  adjoining  States; 
whereas  others,  such  as  Nos.  8.  and  9.,  the  total  thickness  of  which 
is  scarcely  50  feet  in  New  York,  can  be  traced  over  an  area  nearly 
as  large  as  Europe. 

Respecting  the  upper  limit  of  the  above  system,  there  has  been 
very  little  difference  of  ^  opinion,  since  the  Red  Sandstone  No.  1. 
contains  Holoptychius  nobilissimus  and  other  fish  characteristic 
generically  or  specifically  of  the  European  Old  Red.  More  doubt 
has  been  entertained  in  regard  to  the  classification  of  Nos.  10,  11, 
and  12.  M.  de  Verneuil  proposed  in  1847,  after  visiting  the  United 
States,  to  include  the  Oriskany  sandstone  in  the  Devonian  ;  and 
Mr.  D.  Sharpe,  after  examining  the  fossils  which  I  had  collected  in 


CH.  XXVI. ]  IN   THE   UNITED   STATES.  431 

America  in  1842,  arrived  independently  at  the  same  conclusion.* 
The  resemblance  of  the  Spirifers  of  this  Oriskany  sandstone  to  those 
of  the  Lower  Devonian  of  the  Eifel  was  the  chief  motive  assigned 
by  M.  de  Verneuil  for  his  view ;  and  the  overlying  Schoharie  grit, 
No.  10.,  was  classed  as  Devonian  because  it  contained  a  species  of 
Asterolepis.  On  the  other  hand,  Prof.  Hall  adduces  many  fossils 
from  Nos.  10.  and  12.  which  resemble  more  nearly  the  Ludlow 
group  of  Murchison  than  any  other  European  type  ;  and  he  thinks, 
therefore,  that  those  groups  may  be  "  Upper  Silurian."  Although 
the  Oriskany  sandstone  is  no  more  than  30  feet  thick  in  New  York, 
it  is  sometimes  300  feet  thick  in  Pennsylvania  and  Virginia,  where, 
together  with  other  primary  or  paleozoic  strata,  it  has  been  well 
studied  by  Professors  W.  B.  and  H.  D.  Rogers. 

The  upper  divisions  (&om  the  Catskill  to  the  Genessee  groups,  inclu- 
sive, Nos.  1.  to  4.)  consist  of  arenaceous  and  shaly  beds,  and  may  have 
been  of  littoral  origin.  They  vary  greatly  in  thickness,  and  few  of 
them  can  be  traced  into  the  "far  west ;"  whereas  the  calcareous  groups, 
Nos.  8.  and  9.,  although  in  New  York  they  have  seldom  a  united  thick- 
ness of  more  than  50  feet,  are  observed  to  constitute  an  almost  con- 
tinuous coral-reef  over  an  area  of  not  less  than  500,000  square  miles, 
from  the  State  of  New  York  to  the  Mississippi,  and  between 
Lakes  Huron  and  Michigan,  in  the  north,  and  the  Ohio  River  and 
Tenessee  in  the  south.  In  the  Western  States  they  are  represented 
by  the  upper  part  of  what  is  termed  "  the  Cliff  Limestone."  There 
is  a  grand  display  of  this  calcareous  formation  at  the  falls  or  rapids 
of  the  Ohio  River  at  Louisville  in  Kentucky,  where  it  much  re- 
sembles a  modern  coral-reef.  A  wide  extent  of  surface  is  exposed  in 
a  series  of  horizontal  ledges,  at  all  seasons  .when  the  water  is  not 
high ;  and,  the  softer  parts  of  the  stone  having  decomposed  and 
wasted  away,  the  harder  calcareous  corals  stand  out  in  relief,  their 
erect  stems  sending  out  branches  precisely  as  when  they  were 
living.  Among  other  species  I  observed  large  masses,  not  less  than 
5  feet  in  diameter,  of  Favosites  gothlandica,  with  its  beautiful 
honeycomb  structure  well  displayed,  and,  by  the  side  of  it,  the 
Favistella,  combining  a  similar  honeycombed  form  with  the  star  of 
the  Astrcea.  There  was  also  the  cup-shaped  Cyathophyllum,  and 
the  delicate  network  of  the  Fenestella,  and  that  elegant  and  well- 
known  European  species  of  fossil,  called  "  the  chain  coral,"  Cateni- 
pora  escharoides  (see  fig.  579.  p.  439.),  with  a  profusion  of  others. 
These  coralline  forms  were  mingled  with  the  joints,  stems,  and 
occasionally  the  heads  of  lily  encrinites.  Although  hundreds  of  fine 
specimens  have  been  detached  from  these  rocks  to  enrich  the 
museums  of  Europe  and  America,  another  crop  is  constantly  working 
its  way  out,  under  the  action  of  the  stream,  and  of  the  sun  and  rain 
in  the  warm  season  when  the  channel  is  laid  dry.  The  waters  of 
the  Ohio,  when  I  visited  the  spot  in  April,  1846,  were  more  than 

*  De  Verneuil,  Bulletin,  4.  678.,  1847.     D.  Sharpe,  Quart.  Journ.  Geol.  Soc. 
vol.  iv.  pp.  145.,  1847. 


432  DEVONIAN  STRATA.  [Cn.  XXVI. 

40  feet  below  their  highest  level,  and  20  feet  above  their  lowest,  so 
that  large  spaces  of  bare  rock  were  exposed  to  view.* 

No  less  than  46  species  of  British  Devonian  corals  are  described 
in  the  Monograph  published  in  1853  by  Messrs.  M.  Edwards  and 
Jules  Haime  (Paleontographical  Society),  and  only  six  of  these  occur 
in  America ;  a  fact,  observes  Prof.  E.  Forbes,  which,  when  we  call 
to  mind  the  wide  latitudinal  range  of  the  Anthozoa,  has  an  im- 
portant bearing  on  the  determination  of  the  geography  of  the 
northern  hemisphere  during  the  Devonian  epoch.  We  must  also 
remember  that  the  corals  of  these  ancient  reefs,  whether  American 
or  European,  however  recent  may  be  their  aspect,  all  belong  to  the 
Zoantharia  rugosa,  a  suborder  which,  as  before  stated  (p.  407. 
et  seq.\  has  no  living  representative.  Hence  great  caution  must 
be  used  in  admitting  all  inductions  drawn  from  the  presence  and 
forms  of  these  zoophytes,  respecting  the  prevalence  of  a  warm  or 
tropical  climate  in  high  latitudes  at  the  time  when  they  flourished, 
—  for  such  inductions,  says  Prof.  E.  Forbes,  have  been  founded  "  on 
the  mistaking  of  analogies  for  affinities."  f 

This  calcareous  division  also  contains  Goniatites,  Spirifers,  Pen- 
tremites,  and  many  other  genera  of  Mollusca  and  Crinoidea,  corres- 
ponding to  those  which  abound  in  the  Devonian  of  Europe,  and  some 
few  of  the  forms  are  the  same.  But  the  difficulty  of  deciding  on 
the  exact  parallelism  of  the  New  York  subdivisions,  as  above  enu- 
merated, with  the  members  of  the  European  Devonian,  is  very  great, 
so  few  are  the  species  in  common.  This  difficulty  will  best  be 
appreciated  by  consulting  the  critical  essay  published  by  Mr.  Hall 
in  1851,  on  the  writings  of  European  authors  on  this  interesting 
question.^  Indeed  we  are  scarcely  as  yet  able  to  decide  on  the 
parallelism  of  the  principal  groups  even  of  the  north  and  south  of 
Scotland,  or  on  the  agreement  of  these  again  with  the  Devonian 
and  Rhenish  subdivisions. 

*  LyelPs  Second  Visit  to  the  United  J  Report  of  Foster  and  Whitney  on 

States,  vol.  ii.  p.  277.  Geol.  of  L.  Superior,  p.  302.,  Wash- 

t  Geol.  Quart.  Journ.  vol.  x.  p.  Ix,,  ington,  1851. 
1854. 


CH.  XXVII.]  SILURIAN   STRATA.  *   433 


CHAPTER  XXVH. 

SILURIAN   AND   CAMBRIAN   GROUPS. 


Silurian  strata  formerly  called  Transition — Term  Grauwacke —  Subdivisions  of 
Upper,  Middle,  and  Lower  Silurians — Ludlow  formation  and  fossils — Ludlow 
bone -bed,  and  oldest  known  remains  of  fossil  fish — Wenlock  formation,  corals, 
cystideans,  trilobites — Middle  Silurian  or  Caradoc  sandstone  —  Its  unconforma- 
bility — Pentameri  and  Tentaculites — Lower  Silurian  rocks — Llandeilo  flags  — 
Cystidese — Trilobites — Graptolites — Vast  thickness  of  Lower  Silurian  strata  in 
Wales — Foreign  Silurian  equivalents  in  Europe  —  Ungulite  grit  of  Russia — 
Silurian  strata  of  the  United  States — Amount  of  specific  agreement  of  fossils 
with  those  of  Europe — Canadian  equivalents — Deep-sea  origin  of  Silurian 
strata— Fossiliferous  rocks  below  the  Llandeilo  beds  —  Cambrian  group  — 
Lingula  flags  of  North  Wales— Lower  Cambrian — Oldest  known  fossil  re- 
mains—  "Primordial  group"  of  Bohemia — Characteristic  trilobites — Meta- 
morphosis of  trilobites — Alum  schists  of  Sweden  and  Norway — Potsdam  sand- 
stone of  United  States  and  Canada — Footprints  near  Montreal  —  Trilobites  on 
the  Upper  Mississippi — Supposed  period  of  invertebrate  animals  —  Upper 
Silurian  bone-bed — Absence  of  fish  in  Lower  Silurian — Progressive  discovery 
of  vertebrata  in  older  rocks — Inference  to  be  drawn  from  the  greater  success 
of  British  Paleontologists  —  Doctrine  of  the  non-existence  of  vertebrata  in  the 
older  fossiliferous  periods  premature. 

WE  come  next  in  the  descending  order  to  the  most  ancient  of  the 
primary  fossiliferous  rocks,  that  series  which  comprises  the  greater 
part  of  the  strata  formerly  called  "  transition"  by  Werner,  for  reasons 
explained  in  Chap  VHL,  pp.  91.  and  93.  Geologists  were  also  in 
the  habit  of  applying  to  these  older  strata  the  general  name  of 
"  grauwacke,"  by  which  the  German  miners  designate  a  particular 
variety  of  sandstone,  usually  an  aggregate  of  small  fragments  of 
quartz,  flinty  slate  (or  Lydian  stone),  and  clay-slate  cemented  to- 
gether by  argillaceous  matter.  Far  too  much  importance  has  been 
attached  to  this  kind  of  rock,  as  if  it  belonged  to  a  certain  epoch  in 
the  earth's  history,  whereas  a  similar  sandstone  or  grit  is  found  in 
the  Old  Ked,  and  in  the  Millstone  Grit  of  the  Coal,  and  sometimes 
in  certain  Cretaceous  and  even  Eocene  formations  in  the  Alps. 

The  name  of  Silurian  was  first  proposed  by  Sir  Roderick  Mur- 
chison  for  a  series  of  fossiliferous  strata  lying  below  the  Old  Red 
Sandstone,  and  occupying  that  part  of  Wales  and  some  contiguous 
counties  of  England  which  once  constituted  the  kingdom  of  the 
Silures,  a  tribe  of  ancient  Britons.  The  following  table  will  explain 
the  various  formations  into  which  this  group  of  ancient  strata  may 
be  subdivided. 

F  P 


434 


SUBDIVISIONS   OP    SILURIAN   ROCKS.         [Cn.  XXVII. 


UPPER  SILURIAN  ROCKS. 

Prevailing  Lithologi-       Thick, 
cal  characters.  Feet. 


Organic  remains. 


fa.  Tilestones.  —  1 

Finely  laminat-  I 

ed  reddish   and  >  800  ? 

Marine    mollusca    of 

UDTiPl* 

green  micaceous  J 

almost  every  order, 

ypoi 

Ludlow. 

sandstones.         J 

the      Brachiopoda 

most        abundant. 

b.  Micaceous  grey") 

Serpulites.   Crusta- 

1. Ludlow 

sandstone     and 

ceans  of  the  Trilo- 

formation.  " 

^    mudstone. 

bite   family.     Pla- 

coid    fish     (oldest 

Aymestry    i 
limestone.    \ 

r  Argillaceous  lime- 
stone. 

-   2000 

remains  of  fish  yet 
known).           Sea- 

weeds ;  and  in  the 

Lower       I 
Ludlow.     \ 

:  Shale,  with  concre- 
tions   of    lime- 

uppermost     strata 
land  plants. 

\ 

stone. 

- 

Wenlock    J 

"Concretionary  and" 

Marine    mollusca   of 

limestone.   ] 

tnicK-  oeaaea 

various    orders    as 

2.  Wenlock 

I 

limestone. 

Above 

before.      Crinoidea 

formation/ 

Wenlock  J 
.      shale.      \ 

:  Argillaceous  shale, 
frequently  flag- 
stone. 

^   2000 

and  corals  plentiful. 
Trilobites,  Grapto- 
lites. 

Caradoc 
formation 


MIDDLE  SILURIAN  ROCKS. 

f  Shale,  shelly  lime-") 

{Caradoc    J      stone,  sandstone,  ( 
sandstones.  |      and    conglome-  I 
L     rate. 


°?1?' 
chiefly 


abundant.) 


LOWER  SILURIAN  ROCKS. 


Llandeilo 
formation 


r 
.! 


f  Dark  coloured  cal-  "1  -,,  ,, 

Llandeilo    I      careous     flags;  I  20000fM  ' 

flag,      |     .lat^and  sand-j20'000 


UITER   SILURIAN  ROCKS. 

Ludlow  formation.  —  This  member  of  the  Upper  Silurian  group, 
as  will  be  seen  by  the  above  table,  is  of  great  thickness,  and  sub- 
divided into  three  parts,  —  the  Upper  and  the  Lower  Ludlow,  and 
the  intervening  Aymestry  limestone.  Each  of  these  may  be  dis- 
tinguished near  the  town  of  Ludlow,  and  at  other  places  in  Shrop- 
shire and  Herefordshire,  by  peculiar  organic  remains. 

1.  Upper  Ludlow.  a.  Tilestones.  —  This  uppermost  subdivision, 
called  the  Tilestones,  was  originally  classed  by  Sir  R.  Murchison 
with  the  Old  Red  Sandstone,  because  they  decompose  into  a  red 
soil  throughout  the  Silurian  region.  They  were  regarded  as  a  tran- 
sition group  forming  a  passage  from  Silurian  to  Old  Red ;  but  it  is 
now  ascertained  that  the  fossils  agree  in  great  part  specifically,  and 
in  general  character  entirely,  with  those  of  the  underlying  Silurian 


Ce.  XXVII.]  UPPER    SILURIAN   BONE-BED.  435 

strata.  Among  these  are  Orthoceras  bullatum,  Trochus?  helicites, 
Bellerophon  trilobatus,  Chonetes  lata,  &c.,  with  numerous  defences 
of  fishes.  These  beds  are  well  seen  at  Kington  in  Herefordshire, 
and  at  Downton  Castle  near  Ludlow,  where  they  are  quarried  for 
building. 

b.  Grey  Sandstone,  fyc.  —  The  next  subdivision  of  the  Upper 
Ludlow  consists  of  grey  calcareous  sandstone,  or  very  commonly  a 
micaceous  stone,  decomposing  into  soft  mud,  and  contains,  besides 
the  shells  just  quoted,  the  Lingula  cornea,  which  is  common  to  it 
and  the  Tilestone  beds.  The  Orthis  orbicularis,  a  round  variety  of 
0.  elegantula,  is  characteristic  of  the  Upper  Ludlow;  and  the 
lowest  or  mudstone  beds  are  loaded  for  a  thickness  of  30  feet  with 
Athyris  navicula  (fig.  568.).  As  usual  in  strata  of  the  Primary 

Fig.  567  Fig.  568. 


Orthis  elegantult,  Dalm.    VAT.  orbicularis,         Athyris  (Terebratula)  navicula,  J.  Sow. 
J.  Sow.    Delbury.  Aymestry  limestone  ;  also  in 

Upper  Ludlow.  Upper  and  Lower  Ludlow. 

periods,  the  brachiopodous  mollusca  predominate  over  the  lamelli- 
branchiate ;  but  the  latter  are  by  no  means  unrepresented.  Among 
other  genera,  for  example,  we  observe  Avicula  (or  Pterinea),  Car- 
diola,  Nucula,  Sanguinolites,  and  Modiola. 

Some  of  the  Upper  Ludlow  sandstones  are  ripple-marked,  thus 
affording  evidence  of  gradual  deposition ;  and  the  same  may  be  said 
of  the  accompanying  fine  argillaceous  shales  which  are  of  great  thick- 
ness, and  have  been  provincially  named  "mudstones."  In  some 
of  these  shales  stems  of  crinoidea  are  found  in  an  erect  position, 
having  evidently  become  fossil  on  the  spots  where  they  grew  at 
the  bottom  of  the  sea.  The  facility  with  which  these  rocks,  when 
exposed  to  the  weather,  are  resolved  into  mud,  proves  that,  not- 
withstanding their  antiquity,  they  are  nearly  in  the  state  in  which 
they  were  first  thrown  down. 

The  bone-bed  of  the  Upper  Ludlow  deserves  especial  notice 
as  affording  the  oldest  well-authenticated  example  of  the  fossil 
remains  of  fish.  It  usually  consists  of  a  single  thin  layer  of 
brown  bony  fragments  near  the  junction  of  the  Old  Red  Sandstone 
and  the  Ludlow  rocks,  and  was  first  observed  by  Sir  R.  Mur- 
chison,  near  the  town  of  Ludlow,  where  it  is  three  or  four  inches 
thick.  It  has  since  been  traced  to  a  distance  of  45  miles  from  that 
point  into  Gloucestershire  and  other  counties,  and  is  commonly 
not  more  than  an  inch  thick.  At  May  Hill  two  bone-beds  were 
observed,  with  14  feet  of  intervening  strata  full  of  Upper  Lud- 
low fossils.*  At  that  point  immediately  above  the  upper  fish-bed 


*  Murchison's  Siluria,  pp.  137 — 237. 
F  F  2 


436  FOSSILS   OF   UPPER   LUDLOW.  [Cn.  XXVII. 

numerous  globular  bodies  were  found,  which  were  determined 
by  Dr.  Hooker  to  be  the  spores  of  a  cryptogamic  land-plant,  pro- 
bably Lycopodiaceous.  These  beds  occur  just  beneath  the  lowest 
strata  of  the  "  Old  Red."  Some  of  the  fish  are  of  the  shark  family, 
and  their  defences  are  referred  to  the  genus  Onchus  (fig.  569.).  There 
are  also  numerous  minute  shagreen  scales  (fig.  570.),  which  may 

Fig.  569.  Fig.  570. 


Onchus  tenuistriatus,  Agass.  Shagreen-scales  of  a  placoid  fish 

Bone-bed.    Upper  Silurian ;  Ludlow.  (Thelodus). 

Bone-bed.    Upper  Ludlow. 

possibly  belong  to  the  same  placoid  fish.     The  jaw  and  teeth  of 
Fig.  571.  another   predaceous   genus    (fig.  571.)   have 

also  been  detected.    As  usual  in  bone-beds, 
the  teeth  and  bones  are,  for  the  most  part, 
piectrodus  mirabiits,  Agass.      fragmentary  and   rolled.     Many  statements 

Bone-bed.    Upper  Ludlow.        -,  •,  if  11      en-,  •  -, 

have  been  published  ot  fash  remains  obtained 

from  older  members  of  the  Silurian  series  ;  but  Mr.  Salter  has  shown 
all  these  to  be  spurious.*  Professor  Phillips  has,  however,  discovered 
fish-bones  at  the  bottom  of  the  "  Upper  Ludlow,"  at  its  junction  with 
the  Aymestry  Rock  f ;  and  lower  than  this  no  one  seems  as  yet  to 
have  succeeded  in  tracing  them  downwards,  whether  in  Europe  or 
North  America,  for  M.  Barrande's  most  ancient  ichthyolites  (bony 
fragments.  8  inches  long)  occur  in  the  Upper  Silurian  of  Bohemia ; 
and  those  of  the  American  geologists  are  from  the  Oriskany  Sand- 
stone, a  formation  which  is  still  considered  as  debateable  ground 
between  the  Devonian  and  Silurian  systems  (see  p.  430.  above). 

In  England  it  is  true,  as  in  the  United  States  and  Canada,  glo- 
bular, cylindrical,  or  flattened  masses  have  been  detected,  com- 
posed principally  of  phosphate  of  lime,  in  the  Lowest  Silurian  rocks, 
and  they  have  been  suspected  to  be  coprolitic.  Messrs.  Logan  and 
Hunt  have  recently  shown  that  shells  of  the  genera  Lingula  and 
Orbicula,  which  occur  abundantly  in  the  same  formations,  are 
also  made  up  of  phosphate  and  carbonate  of  lime,  mixed  in  the  like 
proportions ;  and  it  has  been  suggested  that  the  decomposition  of  such 
shells  might  give  rise  to  the  nodules  alluded  to  which  may  owe  their 
form  to  concretionary  action.  J  Even  if  the  zoologist  should  think 
it  more  likely  that  the  phosphatic  matter  was  rejected  in  faecal 
lumps,  by  creatures  feeding  on  Lingulae  and  Orbiculse,  we  cannot 
decide  that  such  feeders  were  of  the  vertebrate  class,  rather  than 
Cephalopods,  Crustaceans,  or  some  other  of  the  Invertebrata.  In 
regard  to  the  doctrine  of  the  supposed  non-existence  of  fish  in 
the  Silurian  seas  before  the  time  of  the  Ludlow  bone-bed,  I  shall 
consider  that  question  fully  in  the  concluding  pages  of  this  chapter, 
p.  457.,  et  seq. 

*  Geol.  Quart.  Journ.  vol.  vii.  p.  2C3          J  Logan  and  Hunt;  Silliman's  Jotirn. 
t  Memoirs  Geol.  Surv.  vol  ii.  No.  50.  2d  series,  March  1854. 


CHoXXVII.J  AYMESTRY   LIMESTONE.  437 

2.  Aymestry  limestone.  —  The  next  group  is  a  subcrystalline  and 
argillaceous  limestone,  which  is  in  some  places  50  feet  thick,  and 
distinguished  around  Aymestry  by  the  abundance  of  Pentamerus 
Knightii,  Sow.  (fig.  572.),  also  found  in  the  Lower  Ludlow.  This 

Fig.  572. 


Pentamerus  Knigfitii,  Sow.    Aymestry.    Half  nat.  size. 

a.  view  of  both  valves  united. 

b.  longitudinal  section  through  both  valves,  showing  the  central  plates  or  septa. 

genus  of  brachiopoda  was  first  found  in  Silurian  strata,  and  is  ex- 
clusively a  paleozoic  form.  The  name  was  derived  from  Trerrf,  pente, 
five,  and  fiepoc,  meros,  a  part,  because  both  valves  are  divided  by  a 
central  septum,  making  four  chambers,  and  in  one  valve  the  septum 
itself  contains  a  small  chamber,  making  five.  The  size  of  these  septa 
is  enormous  compared  with  those  of  any  other  brachiopod  shell ;  and 
they  must  nearly  have  divided  the  animal  into  two  equal  halves ; 
but  they  are,  nevertheless,  of  the  same  nature  as  the  septa  or  plates 
which  are  found  in  the  interior  of  Spirifer,  Terebratula,  and  many 
other  shells  of  this  order.  Messrs.  Murchison  and  De  Verneuil  dis- 
covered this  species  dispersed  in  myriads  through 
a  white  limestone  of  Upper  Silurian  age,  on  the 
banks  of  the  Is,  on  the  eastern  flank  of  the  Urals 
in  Russia,  and  a  similar  species  is  frequent  in  Swe- 
den. 

Three  other  abundant  shells  in  the  Aymestry 
limestone  are,  1st,  Lingula  Lewisii  (fig.  573.) ;  2d, 
Rhynchonella  Wilsoni,  Sow.  (fig.  574.),  which  is 
also  common  to  the  Lower  Ludlow  and  Wenlock 
limestone ;  3d,  Atrypa  reticularis,  Lin.  (fig.  575.), 
which  has  a  very  wide  range,  being  found  in  every 
part  of  the  Silurian  system,  even  in  the  upper 
portion  of  the  Llandeilo  flags. 

Fig.  574. 


Fig.  573. 


Lingula  Lewisii, 

J.  Sow. 
Abberlry  Hills. 


Rnynchonella  (Terebratula)  Wilsoni,  Sow.    Aymestry. 

r  F  3 


438 


FOSSILS   OF    LOWER   LUDLOW 

Fig.  5T!» 


[CH.  XXVII. 


Fig.  576. 


Atrypa  reticularis,  Linn.  (Terebratula  affinis,  Min.  Con.)    Aymestry. 
a.  upper  valve.  b.  lower  valve, 

c.  anterior  margin  of  the  valves. 

The  Aymestry  Limestone  contains  so  many  shells,  corals,  and 
trilobites  agreeing  specifically  with  those  of  the  subjacent  Wenlock 
limestone,  that  it  is  scarcely  distinguishable  from  it  by  its  fossils 
alone.  Nevertheless,  many  of  the  organic 
remains  are  common  to  the  Aymestry  lime- 
stone and  the  Upper  Ludlow,  and  several 
of  these  are  not  found  in  the  Wenlock.* 

3.  Lower  Ludlow  shale.- — This  mass  is  a 
dark  grey  argillaceous  deposit,  containing, 
among  other  fossils,  many  large  chambered 
shells  of  genera  scarcely  known  in  newer 
rocks,  as  the  Phragmoceras  of  Broderip, 
and  the  Lituites  of  Breyn  (see  figs.  576, 
577.).  The  latter  is  partly  straight  and 
partly  convoluted,  nearly  as  in  Spirula. 

The   Orthoceras  Ludense  (fig.  578.),   as 
sum,  J.  sow.  well  as  the  cephalopod  last  mentioned,  is 

(Orthvceras  ventricosum,  Stein.)  .  ,,    , 

i  nat.  size.         peculiar  to  this  member  of  the  series. 


Fig.  577. 


Fig.  578. 


Lituites  giganteus,  J.  Sow. 
Near  Ludlow  ;  also  in  the  Aymestry 
and  Wenlock  limestones  ;  £nat.  size. 


Fragment  of  Orthoceras  Ludense,  J.  Sow. 
Leintwarcline,  Shropshire. 


A  species  of  Graptolite,  G.  Ludensis,  Murch.  (fig.  588.,  p.  441.),  a 
form  of  zoophyte  which  has  not  yet  been  met  with  in  strata  above 
the  Silurian,  occurs  plentifully  in  the  Lower  Ludlow. 


Murchison's  Siluria,  p.  133. 


CH.  XXVII.] 


WENLOCK   FOKMATION. 


439 


Wenlock  formation.  —  We  next  come  to  the  Wenlock  formation, 
which  has  been  divided  (see  Table,  p.  434.)  into  the  Wenlock  lime- 
stone and  the  Wenlock  shale. 

1.  The  Wenlock  limestone,  formerly  well  known  to  collectors  by 
the  name  of  the  Dudley  limestone,  forms  a  continuous  ridge  in  Shrop- 
shire, ranging  for  about  20  miles  from  S.W.  to  N.E.,  about  a  mile 
distant  from  the  nearly  parallel  escarpment  of  the  Aymestry  limestone. 
This  ridgy  prominence  is  due  to  the  solidity  of  the  rock,  and  to  the 
softness  of  the  shales  above  and  below  it.  Near  Wenlock  it  consists  of 
thick  masses  of  grey  subcrystalline  limestone,  replete  with  corals  and 
encrinites.  It  is  essentially  of  a  concretionary  nature  ;  and  the  con- 
Fig.  579.  cretions,  termed  "  ball-stones "  in  Shropshire, 
are  often  enormous,  even  80  feet  in  diameter. 
They  are  of  pure  carbonate  of  lime,  the  sur- 
rounding rock  being  more  or  less  argilla- 
ceous.* Sometimes  in  the  Malvern  Hills  this 
limestone,  according  to  Professor  Phillips,  is 
oolitic. 

Among  the  corals  in  which  this  formation 
is  so  rich,  the  "  chain-coral,"  Halysites  catenu- 
latus,  or  Catenipora  escharoides  (fig.  579.), 
may  be  pointed  out  as  one  very  easily  recog- 
nized, and  widely  spread  in  Europe,  ranging 
through  all  parts  of  the  Silurian  group,  from 
the  Aymestry  limestone  to  near  the  bottom  of 
the  series.  Another  coral,  the  Favosites  Goth- 

,        ,.       ,  _        -r.r\  \    •       i  -^  •  c 

landica  (fig.  580.),  is  also  met  with  in  profusion 
in  large  hemispherical  masses,  which  break  up  into  prismatic  frag- 
ments, like  that  here  figured  (fig.  580.).  Another  common  form  in 
the  Wenlock  limestone  is  the  Omphyma  (fig.  581.),  which,  like  many 
of  its  companions,  reminds  us  of  some  modern  cup-corals,  but  all  the 
Silurian  genera  belong  to  the  paleozoic  type  before-mentioned 


Halysites  catenulattis,  Linn.  sp. 
Upper  and  Lower  Silurian. 


Fig.  580. 


Fig.  581. 


Favosites  Gothlandica,  Lam.    Dudley. 
«.  portion  of  a  large  mass  -,  less  than  the 

natural  size. 
b.  magnified  portion  to  show  the  pores 

and  the  partitions  in  the  tubes. 


Omphyma  turbinatum,  Linn.  sp. 

(Cyathophyllum,  Goldf.) 
Wenlock  Limestone,  Shropshire. 


*  Murchison's  Siluria,  p.  115. 

F  P  4 


440  FOSSILS   OF    THE   WENLOCK   LIMESTONE.       [On.  XXVII. 

(p.  407.),  exhibiting  the  quadripartite  arrangement  of  the  lamellae 
within  the  cup. 

Among  the  numerous  Crinoids,  several  peculiar  species  of  Cya- 
thocrinus  (for  genus,  see  figs.  p.  409.)  contribute  their  calcareous 
stems,  arms,  and  cups  towards  the  composition  of  the  Wenlock  lime- 
stone. Of  Cystideans  there  are  a  few  very  remarkable  forms,  some 
of  them  peculiar  to  the  Upper  Silurian  formation,  as  for  example 
the  Pseudocrinites,  which  was  furnished  with  pinnated  fixed  arms  *, 
as  represented  in  the  annexed  figure  (fig.  582.). 

The  Brachiopoda  are  for  the  most  part  of  the  same  species  as  those 
of  the  Aymestry  limestone ;  as,  for  example,  Atrypa  reticularis  (fig. 
575.,  p.  438.),  and  Strophomena  depressa,  Sow.  sp.  (fig.  583.) ;  but 
these  species  range  also  through  the  Ludlow  rocks,  Wenlock  shale, 
and  Caradoc  Sandstone. 


Fig.  582. 


Fig.  583. 


Strophomena  (Leplcena)  depressa,  Sow. 
Wenlock  and  Ludlow  Rocks. 


Pseudocrinites  bifasciatus,  Pearce. 
Wenlock  Limestone,  Dudley. 

The  Crustaceans  are  represented  almost  exclusively  by  Trilobites, 
which  are  very  conspicuous.  The  Calymene  Blumenbachii,  called 
the  "  Dudley  Trilobite,"  was  known  to  collectors  long  before  its  true 
place  in  the  animal  kingdom  was  ascertained.  It  is  often  found 
coiled  up  like  the  common  Oniscus  or  wood-louse,  and  this  is  so 
common  a  circumstance  among  the  trilobites  as  to  lead  us  to 
conclude  that  they  must  have  habitually  resorted  to  this  mode  of 
protecting  themselves  when  alarmed.  Sphcerexochus  mirus  (fig.  586.) 


Fig.  585. 


Fig.  584. 


Calymene  Blumenbachii, 

Brong. 

Wenlock,  Ludlow,  and 
Aymestry  limestones. 


Fig.  586. 


SpJi&rexochus  mirus,  Beyrich. 

coiled  up. 

Dudley  ;  also    in  Ohio, 
N.  America. 


Phacops  caudatus,  Brong. 
Wenlock,  Aymestry,  and  Ludlow  Rocks. 

*  E.  Forbes,  Mem.  Geol.  Survey,  vol.  ii.  p.  496. 


MIDDLE    SILURIAN   ROCKS. 


441 


Fig.  587. 


CH.  XXVII.] 

is  almost  a  globe  when  rolled  up,  the  forehead  of  this  species  being 
extremely  inflated.  The  Homalonotus,  a  form  of  Trilobite  in  which 
the  tripartite  division  of  the  dorsal  crust  is 
almost  lost  (see  fig.  587.),  is  very  characteristic 
of  this  division  of  the  Silurian  series. 

2.   The  Wenlock  Shale.  —  This,  observes  Sir  K. 
Murchison  *,  is  infinitely  the  largest  and  most 
persistent  member  of  the  Wenlock  formation,  for 
the  limestone  often  thins  out  and  disappears.  The 
shale,   like   the   Lower  Ludlow,  often   contains 
elliptical  concretions  of  impure  earthy  limestone. 
In  the  Malvern  district  it  is  a  mass  of  finely  le- 
vigated argillaceous  matter,  attaining,  according 
to  Prof.  Phillips,  a  thickness  of  640  feet,  but  it 
is  sometimes  more  than  1000  feet  thick  in  Wales. 
The  prevailing  fossils,  besides  corals  and  trilo- 
bites,  and  some  crinoids,  are  several  small  species 
of  Orihis,  with  other  brachiopods  and  certain  thin- 
shelled  species  of  Orthoceratites.     One  species  of 
GraPtolite,  *>  group  of  zoophytes  before  alluded 
to  as  being  confined  to  Silurian  rocks,  is  very 
abundant  in  this  shale,  and  occurs 
more  sparingly  in  "  the  Ludlow." 
Of  these  fossils,   which   are   more 
characteristic  of  the  Lower  Silurian, 
I  shall  again  speak  in   the  sequel 
(p.  446.). 


Castle;  §nat.  size 


Fig.  588. 

^*>^^^ 

Graptolilhus  Ludensis,  Murchison. 
Ludlow  and  Wenlock  Shales. 


MIDDLE    SILURIAN  ROCKS. 

Caradoc  Sandstone. — This  sandstone,  so  named  from  a  mountain 
called  Caer  Caradoc,  in  Shropshire,  was  originally  considered  by 
Sir  Roderick  Murchison  as  the  sandy  and  upper  portion  of  the 
Lower  Silurian  strata.  Subsequent  investigations  have  led  to  the 
conclusion  that  the  original  or  typical  Caradoc  is  divisible  into  two 
formations, — the  lower,  an  arenaceous  form  of  the  Llandeilo  flags, 
and  containing  identical  species  of  fossils ;  the  other  or  superior 
sandstone,  a  series  of  strata  resting  unconformably  on  the  Llandeilo 
beds,  and  chiefly  characterized  by  Upper  Silurian  fossils,  yet  having 
some  intermixture  of  species  common  to  the  "Lower  Silurian." 
Hence  the  Caradoc,  as  distinct  from  the  Llandeilo,  must  either  be 
classed  as  the  base  of  the  Wenlock  Shale,  an  opinion  to  which  some 
authorities  incline, — or  it  may  be  regarded  as  a  Middle  Silurian 
group,  an  alternative  which  I  have  embraced  provisionally  in  common 
with  many  officers  of  our  Government  Survey.  The  larger  part, 
therefore,  of  what  was  once  termed  "  the  Caradoc  "  has  merged  into 
the  Llandeilo,  and  is  the  equivalent  of  the  upper  and  middle  portions 
of  that  division. 

The  first  step  towards  placing  in  a  clearer  light  the  relations  of 
"the  Caradoc  "  to  the  strata  above  and  below  it,  was  made  in  1848 
*  Siluria,  p.  111. 


442  CARADOC    SANDSTONE.  [Cn.  XXVII. 

by  Professor  Ramsay  and  Mr.  Aveline,  who  observed  that  in  the 
Longmynd  Hills  the  Caradoc  sandstone  rested  un conformably  on 
the  Lower  Silurian,  and  that  the  latter  or  "  Llandeilo  flags,"  together 
with  some  still  older  rocks,  must  have  constituted  an  island  in  the 
Caradoc  sea.  Professor  E.  Forbes  at  the  same  time  observed  that 
the  island  was  probably  high  and  steep  land  rising  from  a  deep  sea, 
and  that  the  Caradoc  fossils,  some  of  them  of  littoral  aspect,  as 
Littorina  and  Turritella,  were  deposited  round  the  margin  of  that 
ancient  land.  It  was  also  remarked  that  while  the  sandstone  and 
conglomerate  of  this  upper  Caradoc  *  reposed  unconformably  on  the 
Llandeilo  beds,  it  at  the  same  time  graduated  upwards,  as  Sir  R. 
Murchison  had  stated,  into  the  Wenlock  Shale. 

Subsequently  Professor  Sedgwick  and  Mr.  M'Coy,  pursuing  their 
investigations  independently  of  the  Survey  in  North  Wales,  became 
convinced  f  that  the  Caradoc  beds  of  May  Hill  and  the  Malverns, 
constituting  the  Upper  Caradoc,  already  mentioned,  were  full  of 
Upper  Silurian  fossils ;  and  that  the  strata  of  Caradoc  sandstone  at 
Horderly  and  other  places  east  of  Caer  Caradoc  belonged  to  the 
Bala  group  (or  equivalent  of  the  Llandeilo),  being  distinguished  by 
Lower  Silurian  species.  This  opinion  was  finally  substantiated  by 
Mr.  Salter  and  Mr.  Aveline,  in  1853,  by  an  appeal  to  parts  of 
Shropshire  where  "  the  Caradoc  "  had  been  originally  studied  by 
Sir  R.  Murchison,  and  where  they  found  the  Upper  Caradoc  uncon- 
formable  on  the  lower,  and  filled  with  a  series  of  very  distinct  fossils.  J 

In  the  restricted  sense,  therefore,  in  which  it  is  now  understood, 
the  Caradoc  Sandstone  comprises  a  series  of  beds  of  passage  from 
the  Lower  to  the  Upper  Silurian  group.  It  is  everywhere  cha- 
racterized by  species  of  Pentamerus  and  Atrypa  unknown  in  the 
overlying  Wenlock  or  Ludlow  beds,  but  which  descend  into  the 
strata  of  the  Llandeilo  group.  Pentamerus  Icevis  (fig.  589.),  and 

Fig.  589. 


Pentamerus  ltevi$,  Sow.    Caradoc  Sandstone. 
Perhaps  the  young  of  Pentamerus  oblongus. 
a,  b.  Views  of  the  shell  itself,  from  figures  in  Murchison's  Sil.  Syst. 

c.  Cast  with  portion  of  shell  remaining,  and  with  the  hollow  of  the  central  septum  filled  with  spar. 

d.  Internal  cast  of  a  valve,  the  space  once  occupied  by  the  septum  being  represented  by  a  hollow  in 

which  is  seen  a  cast  of  the  chamber  within  the  septum. 

*  Quart.  Geol.  Journ.,  voLiv.  p.  297.          J  Geol.  Quart.  Journ.,  vol.  x.  p.  62. 
f  Geol.  Quart.  Journ.,  1852. 


CH.  XXVII.]  LOWER   SILURIAN   ROCKS.  443 

P.  oblongus  may  be  particularly  mentioned  as  brachiopods  which 
abounded  in  Siluria,  arid  had  a  very  wide  geographical  range,  being 
Fi    59Q  met  with  in  the  same  place  in  the  Silurian 

series  of  Russia  and  the  United  States. 
Among  its  fossils,  too,  Tentaculites  an- 
nulatus  (fig.  590.),  an  annelid  probably 
allied  to  Serpula,  is  exceedingly  common. 
This  also  is  a  link  to  connect  it  with  the 
Lower  rather  than  the  Upper  Silurian. 
annuiatus,  Schiot.  All  the  shelly  sandstone  of  the  Malvern 

Interior  casts  in  sandstone.  j    * -i  -i       i      TT*n         /?  r-r\  ,-1    •      s~\-i 

Eastnor  Park  ;  n»t  size,  and  mag-      and  Abberly  Hills,  of  TortWOrth  in  G10U- 

nified-  cestershire,  and  of  the  centre  of  the  May 

Hill  and  Woolhope  districts  belong  to  this  Middle  Silurian,  which 
in  the  Malvern  range  attains  d,  thickness  of  600  feet.  Of  the  same 
age  are  dense  masses  of  sandstone  with  shale,  2000  feet  in  thickness, 
in  the  higher  and  disturbed  regions  of  North  Wales,  as  in  the 
Berwyn  Mountains  for  example.  According  to  Professor  Sedgwick 
the  hard  quartzose  Coniston  Grits  of  Westmoreland  may  also  be 
referred  to  the  same  period. 

LOWER   SILURIAN  ROCKS. 

Llandeilo  Flags.  —  The  Lower  Silurian  strata  were  originally 
divided  by  Sir  R.  Murchison  into  an  upper  group,  already  described, 
and  termed  the  Caradoc  Sandstone,  and  a  lower  one,  called,  from  a 
town  in  Caermarthenshire,  the  Llandeilo  flags.  The  strata  last  men- 
tioned consist  of  dark-coloured  micaceous  flags,  frequently  calcareous, 
with  a  great  thickness  of  shales,  generally  black,  below  them.  The 
same  beds  are  also  seen  at  Builth  in  Radnorshire,  and  here  they 
are  interstratified  with  volcanic  matter.  Above  these  typical 
Llandeilo  beds,  however,  the  Lower  Silurian  contains,  both  in 
North  and  South  Wales,  some  strata  in  which  the  Pentameri  of 
the  Middle  Silurian,  already  alluded  to  (p.  442.),  are  associated 
with  species  of  fossils  identical  with  those  in  the  Llandeilo  flags. 
The  corals  of  the  calcareous  zone  of  the  Llandeilo  belong  to 
the  genera  Haly sites  (see  fig.  579.),  Heliolites,  Petraia,  Stenopora, 
Favosites  (fig.  580.),  and  others*;  and  there  are  peculiar  Crinoids 
and  Cystideans  in  the  same  rocks.  These  last  are  amongst  the 
most  recent  additions  made  by  paleontologists  to  the  Radiata. 
Their  structure  and  relations  were  first  elucidated  in  an  essay 
published  by  Von  Buch  at  Berlin  in  1845.  They  are  the  Sphce- 
ronites  of  old  authors,  and  are  usually  met  with  as  spheroidal 
bodies  covered  with  polygonal  plates,  with  a  mouth  on  the  upper 
side,  and  a  point  of  attachment  for  a  stem  (which  is  almost  always 
broken  off)  on  the  lower  (fig,  591.  b).  They  are  considered  by 
Professor  E.  Forbes  as  intermediate  between  the  crinoids  and  echi- 
noderms.  The  Sphaeronite  here  represented  (fig.  591.)  occurs  in 
the  Llandeilo  beds  in  Wales  f ,  as  also  in  Sweden  and  Russia. 

*  Murchison's  Siluria,  p.  178.  f  Quart.  Geol.  Journ.  vol.  vii.  p.  11.; 

and  Mem.  Geol.  Surv.  vol.  ii.  p.  r>18, 


444 


LOWER    SILURIAN    ROCKS. 


[CH.  XXVII. 


Examples  are  not  wanting,  though 
very  rare,  of  star-fish  in  the  same  beds. 
Brachiopod  shells  are  in  the  greatest 
abundance,  chiefly  of  the  genera  Orthis, 
Leptana,  and  Strophomena  (fig.  591.). 
Of  the  Orthides  those  species  with 
broad  simple  ribs  (fig.  592.)  are  parti- 
cularly characteristic.  Such  shells  as 
Atrypa  and  Spirifer,  so  frequent  in  the 
Upper  and  Middle  Silurian,  are  rare  or 
confined  to  the  superior  part  of  the 
Lower  Silurian,  while  Chonetes  and 
Productus  are  wholly  absent.  It  is  re- 
markable, however,  that  Rhynchonella 
and  Lingula,  genera  of  which  there  are 

living   representatives  in  the   present  seas,  were  common   in  the 

Silurian  ocean. 


Echinosphcerites  balttcus,  Eichwald,  sp. 
(Of  the  family  Cystidece.) 

a.  mouth 

b.  point  of  attachment  of  stem. 
Lower  Silurian,  S.  &  N.  Wales. 


Fig.  592. 


Fig.  593. 


Fig.  594. 


Or  this  tricenaria, 

Hall. 

New  York.  Canada. 
$  nat.  size. 


Or  this  vespertilio,  Sow. 
Shropshire  ;  N.  &  S. 

Wales. 
|  nat.  size. 


Strophomena  (Orthis)  grandis,  Sowerby. 

|  nat.  size. 

Horderly,  Shropshire  ;  also  Coniston, 
Lancashire. 


Among  the  Cephalopoda  are  Orthoceratites,  with  the  siphuncle  of 
large  dimensions  and  placed  on  one  side ;  also  Lituites  (see  fig.  577.), 
Bellerophon  (see  p.  411.),  and  some  of  the  floating  tribes  of  mol- 
lusca  (Pteropods).  The  Crustaceans  were  plentifully  represented 
by  the  Trilobites,  which  appear  to  have  swarmed  in  the  Silurian 
seas  just  as  crabs  and  shrimps  do  in  our  own.  The  genera  Asaphus 
(fig.  595.),  Ogygia  (fig.  596.),  and  Trinucleus  (figs.  597,  598.)  are 


Fig.  595. 


Fig.  596. 


Asaphus  tyrannus,  Murch. 
Llandeilo  ;  Bishop's  Castle,  &c. 


Osycia  Pucfiii,  Burm.  (Asaphus 

Buchif,  Brongn.) 
Builth.  Radnorshire  ;  Llandeilo,  Caermarthenshire. 


CH.  XXVII.] 


LLANDEILO   FLAGS. 


445 


especially  characteristic  of  strata  of  this  age,  if  not  entirely  con- 
fined to  them;  but  very  numerous  other  genera  accompany  these. 
Burmeister,  in  his  work  on  the  organization  of  trilobites,  supposes 
them  to  have  swum  at  the  surface  of  the  water  in  the  open  sea  and 
near  coasts,  feeding  on  smaller  marine  animals,  and  to  have  had  the 
power  of  rolling  themselves  into  a  ball  as  a  defence  against  injury. 
He  was  also  of  opinion  that  they  underwent  various  transformations 
analogous  to  those  of  living  crustaceans.  M.  Barrande,  author  of  an 
admirable  work  on  the  Silurian  rocks  of  Bohemia,  confirms  the  doctrine 
of  their  metamorphosis,  having  traced  more  than  twenty  species 
through  different  stages  of  growth  from  the  young  state  just  after 
its  escape  from  the  egg  to  the  adult  form.  He  has  followed  some  of 
them  from  a  point  in  which  they  show  no  eyes,  no  joints  to  the  body, 
and  no  distinct  tail,  up  to  the  complete  form  with  the  full  number 
of  segments.  This  change  is  brought  about  before  the  animal  has 
attained  a  tenth  part  of  its  full  dimensions,  and  hence  such  minute 
and  delicate  specimens  are  rarely  met  with.  Some  of  his  figures  of 
the  metamorphoses  of  the  common  Trinucleus  are  copied  in  the 
annexed  wood-cuts  (figs.  597,  598.). 

Fig.  598. 


Young  individuals  of  Trinucleus  con- 
cenlricus  (T.  ornatus,  Barr.) 

a.  Youngest  state.    Natural  size  and 

magnified;  the  body  rings  not 
at  all  developed. 

b.  A  little  older.    One  thorax  joint. 

c.  Still  more  advanced.  Three  thorax 

joints.  The  fourth,  fifth,  and 
sixth  segments  are  successively 
produced,  probably  each  time  the 
animal  moulted  its  crust. 

Trinucleus  concentricus,  Eaton. 

Syn.  T.  caractnci,  Murch. 

N.  Ireland  ;  Wales  ;  Shropshire  ;  N.  America  ; 

Bohemia. 

A  still  lower  part  of  the  Llandeilo  or  Bala  rocks  consists  of  a  black 
carbonaceous  slate  of  great  thickness,  frequently  containing  sulphate 
of  alumina  and  sometimes,  as  in  Dumfriesshire,  beds  of  anthracite. 
It  has  been  conjectured  that  this  carbonaceous  matter  may  be  due  in 
great  measure  to  large  quantities  of  imbedded  animal  remains,  for 
the  number  of  Graptolites  included  in  these  slates  was  certainly  very 
great.  I  collected  these  same  bodies  in  great  numbers  in  Sweden 
and  Norway  in  1835-6,  both  in  the  higher  and  lower  graptolitic 
shales  of  the  Silurian  system ;  and  was  informed  by  Dr.  Beck  of 
Copenhagen,  that  they  were  fossil  zoophytes  related  to  the  Vigularia 
and  Pennatula,  genera  of  which  the  living  species  now  inhabit  mud 
and  slimy  sediment.  The  most  eminent  naturalists  still  hold  to  this 
opinion. 


446  THICKNESS    OF    SILURIAN    STRATA.       [CH.  XXVII. 

Fig.  599. 


Fig.  600. 


Didymograpstis  geminus,  Hisinger,  sp. 
Sweden. 

a,  b.  Didymograpsus  (Graptolites)  Mur- 

ctiiionii,  Beck. 
Llandeilo  flags.    Wales. 

Fig  601. 

!/;  . 

Fig.  602.  Fig.  603. 


Diploprapsus  folium,  Diplograpsus  pristis, 

Hisinger.  Hisinger.  sp. 

llastrites  peregrfnus,  Barrande.  Sc°tland  ;  Sweden'  Shropshire  ;  Wales  ;  Sweden, 

Scotland  ;  Bohemia  ;  Saxony. 

Beneath  the  black  slates  above  described  no  graptolites  appear  as 
jet  to  have  been  found,  but  the  characteristic  shells  and  trilobites  of 
the  Lower  Silurian  rocks  are  still  traceable  downwards,  in  North 
and  South  Wales,  through  a  vast  depth  of  shaly  beds,  interstratified 
with  trappean  formations,  sometimes  not  less  in  their  aggregate 
thickness  than  11, 000  feet.  Hence  the  total  thickness  of  the  beds 
assigned  to  the  Lower  Silurian,  or  the  Llandeilo  group  of  Murchison, 
is  not  less  than  20,000  feet,  and  the  Upper  Silurian  rocks  are  above 
5000  feet  in  addition.  If  these  beds  were  all  exclusively  of  sedi- 
mentary origin  we  might  well  expect,  from  the  analogy  of  other 
parts  of  the  earth's  crust,  to  find  that  they  must  be  referred  pale- 
ontologically  to  more  than  one  era ;  in  other  words,  that  changes  in 
animal  and  vegetable  life,  as  great  as  those  which  occurred  in  the 
course  of  several  such  periods  as  the  Devonian,  Carboniferous,  and 
Permian,  would  be  found  to  have  taken  place  while  the  accumulation 
of  so  enormous  a  pile  of  rocks  was  effected.  But  in  volcanic  archi- 
pelagos, as  in  the  Canaries  for  example,  we  see  the  most  active  of  all 
known  causes,  aqueous  and  igneous,  simultaneously  at  work  to 
produce  great  results  in  a  comparatively  moderate  lapse  of  time. 
The  outpouring  of  repeated  streams  of  lava, — the  showering  down 
upon  land  and  sea  of  volcanic  ashes, — the  sweeping  seaward  of  loose 
sand  and  cinders,  or  of  rocks  ground  down  to  pebbles  and  sand,  by 
torrents  descending  steeply  inclined  channels,  —  the  undermining 
and  eating  away  of  long  lines  of  sea-cliff  exposed  to  the  swell 
of  a  deep  and  open  ocean,  —  above  all,  the  injection,  both  above 
and  below  the  sea-level,  of  sheets  of  melted  matter  between  the 
lavas  previously  formed  at  the  surface, — these  operations  may 
combine  to  produce  a  considerable  volume  of  superimposed  matter, 
without  there  being  time  for  any  extensive  change  of  species. 


CH.  XXVII.]       SILURIAN   EQUIVALENTS   IN   EUROPE.  447 

Nevertheless,  there  would  seem  to  be  a  limit  to  the  thickness  of 
stony  masses  formed  even  under  such  favourable  circumstances, 
for  the  analogy  of  tertiary  volcanic  regions  lends  no  countenance 
to  the  notion  that  sedimentary  and  igneous  rocks  25,000,  much  less 
45,000  feet  thick,  like  those  of  Wales,  could  originate  while  one  and 
the  same  fauna  should  continue  to  people  the  earth.  If,  then,  we 
allow  that  25,000  feet  of  matter  may  be  ascribed  to  one  system,  such 
as  the  Silurian,  from  the  top  of  "  the  Ludlow "  to  the  base  of  "  the 
Llandeilo  "  inclusive,  we  may  be  prepared  to  find  in  the  next  series 
of  subjacent  rocks,  the  commencement  of  another  assemblage  of 
species,  or  even  in  part  of  genera,  of  organic  remains.  Such  appears 
to  be  the  fact,  and  I  shall  therefore  conclude  with  the  Llandeilo 
beds,  the  original  base-line  of  Sir  R.  Murchison,  my  account  of  the 
Silurian  formations  in  Great  Britain,  and  proceed  to  say  something 
of  their  foreign  equivalents,  before  treating  of  rocks  older  than  the 
Silurian. 

It  would  lead  me  into  too  long  a  digression  to  attempt  to  follow 
the  Upper,  Middle,  and  Lower  Silurian  into  Scotland,  the  lake 
country,  Cornwall,  and  other  parts  of  the  British  Isles.  For  an 
account  of  these  rocks  in  Ireland,  the  reader  is  referred  to  Col.  Port- 
lock's  Report  on  Tyrone,  to  the '  writings  of  Mr.  Griffith  and 
Prof.  M'Coy,  and  those  of  the  officers  of  the  Government  Survey, 
as  well  as  to  the  sketch  recently  given  by  Sir  R.  L  Murchison. 

When  we  turn  to  the  Continent  of  Europe,  we  discover  the  same 
ancient  series  occupying  a  wide  area,  but  in  no  region  as  yet  has  it 
been  observed  to  attain  great  thickness.  Thus,  in  Norway  and 
Sw°den,  the  total  thickness  of  strata  of  Silurian  age  is  scarcely 
equal  to  1000  feet*,  although  the  representatives  both  of  the 
Upper  and  Lower  Silurian  of  England  are  not  wanting  there,  and 
even  some  beds  of  schist  have  been  comprehended  which,  as  we 
shall  hereafter  see,  lie  below  the  Llandeilo  group.  In  Russia  the 
Silurian  strata,  so  far  as  they  are  yet  known,  seem  to  be  even  of 
smaller  vertical  dimensions  than  in  Scandinavia,  and  they  appear  to 
consist  chiefly  of  Middle  and  Lower  Silurian,  or  of  a  limestone 
containing  Pentamerus  oblongus,  below  which  are  strata  with  fossils 
corresponding  to  those  of  the  Llandeilo  beds  of  England.  The 
lowest  rock  with  organic  remains  yet  discovered  is  "  the  Ungulite  or 
Obolus  grit "  of  St.  Petersburg,  probably  coeval  with  the  Llandeilo, 
and  not  exhibiting  any  of  those  peculiar  forms  which  distinguish 
"  the  Lingula  flags  "  of  Wales,  or  the  Bohemian  "  primordial  fauna  " 
of  Barrande. 

The  shales  and  grits  near  St.  Petersburg,  above  alluded  to,  contain 
green  grains  in  their  sandy  layers,  and  are  in  a  singularly  unaltered 
state,  taking  into  account  their  high  antiquity.  The  prevailing 
brachiopods  consist  of  the  Obolus  or  Ungulite  of  Pander,  and  a 
Siphonotreta  (see  figs.  604,  605.).  As  bearing  on  the  antiquity 
of  this  formation,  it  is  interesting  to  notice  that  both  genera  have 
recently  been  found  in  our  own  Dudley  limestone. 

*  Murchison's  Siluria,  p.  321. 


448 


SILURIAN    STRATA   OF   UNITED    STATES.       [Cn.  XXVII. 

Shells  of  the  lowest  known  Fossiliferous  Beds  in  Russia. 
Fig.  604.  Fig.  605. 


Siphonotreta  vnguiculata,  Eichwald. 

From  the  Lowest  Silurian  sandstone,  "  Obolus 

grits,"  of  Petersburg. 

a.  outside  of  perforated  valve. 

b.  interior  of  same,  showing  the  termination  of 

the  foramen  within. 


Obolus  Apollinis,  Eichwald. 
From  the  same  locality. 

a.  interior  of  the  larger  or  ventral  valve. 

b.  exterior  of  the  upper  (dorsal)  valve. 

(Davidson.) 


Among  the  green  grains  of  the  sandy  strata  above  mentioned, 
Professor  Ehrenberg  has  recently  (1854)  announced  his  discovery  of 
remains  of  foraminifera.  These  are  casts  of  the  cells ;  and  amongst 
five  or  six  forms  three  are  considered  by  him  as  referable  to  existing 
genera  (e.  g.,  Textularia,  Rotalia,  and  Guttulina). 


SILURIAN   STRATA  OF    THE   UNITED    STATES. 

The  position  of  some  of  these  strata,  where  they  are  bent  and 
highly  inclined  in  the  Appalachian  chain,  or  where  they  are  nearly 
horizontal  to  the  west  of  that  chain,  is  shown  in  the  section,  fig.  505. 
p.  392.  But  these  formations  can  be  studied  still  more  advanta- 
geously north  of  the  same  line  of  section,  in  the  States  of  New  York, 
Ohio,  and  other  regions  north  and  south  of  the  great  Canadian  lakes. 
Here  they  are  found,  as  in  Russia,  nearly  in  horizontal  position,  and 
are  more  rich  in  well-preserved  fossils  than  in  almost  any  spot  in 
Europe.  In  the  State  of  New  York,  where  the  succession  of  the 
beds  and  their  fossils  have  been  most  carefully  worked  out  by  the 
Government  Surveyors,  the  subdivisions  given  in  the  first  column  of 
the  annexed  list  have  been  adopted. 

Subdivisions  of  the  Silurian  Strata  of  New  York.     (Strata  below 
the  Oriskany  Sandstone,  see  Table,  p.  430.) 

New  York  Names.  British  Equivalents. 

1.  Upper  Pen  tamer  us  Limestone  "| 

2.  Encrinal  Limestone         ,    , 

3.  Delthyris  Shaly  Limestone 

4.  Pentamerus  Limestone 

5.  Tentaculite  Limestone 

6.  Onondaga  Salt-group 

7.  Niagara  Group  J 

8.  Clinton  Group  ~\ 

9.  Medina  Sandstone  I  Middle  Silurian  (or  Caradoc  Sand- 

|      stone). 

1 


Upper  Silurian    (or   Ludlow  and 
Wenlock  formations). 


10.  Oneida  Conglomerate 

11.  Grey  Sandstone 

12.  Hudson  River  Group. 

13.  Utica  Slate 

14.  Trenton  Limestone 

15.  Black-River  Limestone 

1 6.  Bird's-Eye  Limestone 

17.  Chazy  Limestone 

18.  Calciferous  Sandstone 


Lower  Silurian  (or  Llandeilo  beds). 


19.  Potsdam  Sandstone 


f  Cambrian  ?  (or  Lingula  flags  and 
\     beds,  older  than  "  the  Llandeilo  "\ 

In  the  second  column  of  the  same  table  I  have  added  the  supposed 
British  equivalents.     All  paleontologists,  European  and  American, 


CH.  XXVII.]         SPECIFIC   AGREEMENT   OF    FOSSILS.  449 

such  as  MM.  de  Verneuil,  D.  Sharpe,  Prof.  Hall,  and  others,  who  have 
entered  upon  this  comparison,  admit  that  there  is  a  marked  general 
correspondence  in  the  succession  of  fossil  forms,  and  even  species,  as 
we  trace  the  organic  remains  downwards  from  the  highest  to  the 
lowest  beds  ;  but  it  is  impossible  to  parallel  each  minor  subdivision. 
In  regard  to  the  three  following  points  there  is  little  difference  of 
opinion. 

1st.  That  the  Niagara  Limestone,  No.  7.,  over  which  the  river  of 
that  name  is  precipitated  at  the  great  cataract,  together  with  its 
underlying  shales,  corresponds  to  the  Wenlock  limestone  and  shale  of 
England.  Among  the  species  common  to  this  formation  in  America 
and  Europe  are  Calymene  Blumenbachii,  Homalonotus  delphinoce- 
phalus  (fig.  587.),  with  several  other  trilobites ;  Rhynchonella  Wilsoni, 
and  R.  cuneata  ;  Orthis  elegantula,  Pentamerus  galeatus,  with  many 
more  brachiopods ;  Orthoceras  annulatum,  among  the  cephalopodous 
shells ;  and  Favosites  gothlandica,  with  other  large  corals. 

2nd.  That  the  Clinton  Group,  No.  8.,  containing  Pentamerus 
oblongus  and  P.  Icevis,  and  related  more  nearly  by  its  fossil  species 
with  the  beds  above  than  with  those  below,  is  the  equivalent  of  the 
Middle  Silurian  as  above  defined,  p.  441. 

3rd.  That  the  Hudson  River  Group,  No.  12.,  and  the  Trenton 
Limestone,  No.  14.,  agree  paleontologically  with  the  Llandeilo  flags, 
containing  in  common  with  them  several  species  of  trilobites,  such 
as  Asaphus  (Isotelus)  gigas,  Trinucleus  concentricus  (fig.  598.  p.  445.); 
and  various  shells,  such  as  Orthis  striatula,  Orthis  biforata  (or  0.  lynx), 
O.  porcata  (0.  occiden tails  of  Hall),  Bellerophon  bilobatus,  &c.* 

Mr.  D.  Sharpe,  in  his  report  on  the  mollusca  collected  by  me  from 
these  strata  in  North  America  f ,  has  concluded  that  the  number  of 
species  common  to  the  Silurian  rocks  on  both  sides  of  the  Atlantic 
is  between  30  and  40  per  cent.;  a  result  which,  although  no  doubt 
liable  to  future  modification,  when  a  larger  comparison  shall  have 
been  made,  proves,  nevertheless,  that  many  of  the  species  had  a  wide 
geographical  range.  It  seems  that  comparatively  few  of  the  gas- 
teropods  and  lamellibranchiate  bivalves  of  North  America  can  be 
identified  specifically  with  European  fossils,  while  no  less  than  two- 
fifths  of  the  brashiopoda,  of  which  my  collection  chiefly  consisted, 
are  the  same.  In  explanation  of  these  facts,  it  is  suggested  that 
most  of  the  recent  brachiopoda  (especially  the  orthldiform  ones)  are 
inhabitants  of  deep  water,  and  that  they  may  have  had  a  wider  geo- 
graphical range  than  shells  living  near  shore.  The  predominance  of 
bivalve  mollusca  of  this  peculiar  class  has  caused  the  Silurian  period 
to  be  sometimes  styled  "  the  age  of  brachiopods." 

The  calcareous  beds,  Nos.  15,  16,  17,  and  18.,  below  the  Trenton 
Limestone  have  been  considered  by  M.  de  Verneuil  as  Lower 
Silurian,  because  they  contain  certain  species,  such  as  Asaphus 
(Isotelus)  gigas,  Illcenus  crassicauda,  and  Orthoceras  bilineatum,  in 
common  with  the  overlying  Trenton  Limestone. if  But,  according  to 

*  See  Murchison's  Siluria,  p.  414.  J  Soc.    Geol.   France,  Bulletin, 

f  Quart.  Geol.  Journ.,  vol.  iv.  vol.  iv.  p.  651.  1847. 

G  G 


450  CANADIAN   EQUIVALENTS.  [Cn.  XXVII. 

Prof.  Hall,  the  Illfsnus  was  erroneously  identified,  an  error  to  which 
he  confesses  that  he  himself  contributed ;  and  on  the  whole  these 
lower  beds  contain,  he  thinks,  a  very  distinct  set  of  species,  only 
three  or  four  of  them  out  of  eighty -three  passing  upwards  into  the 
incumbent  formations.* 

Be  this  as  it  may,  the  Black  River  Limestone,  No.  15.,  contains 
certain  forms  of  Orthoceras  of  enormous  size  (some  of  them  8  or 
9  feet  long !),  of  the  subgenera  Ormoceras  and  Endoceras,  seeming 
to  represent  the  Lower  Silurian  or  Orthoceras  limestone  of  Sweden. 
Moreover,  the  general  facies  of  the  fauna  of  all  these  beds  is 
essentially  similar.  Another  ground  for  extending  our  comparison 
of  the  Llandeilo  beds  of  Europe  as  far  down  as  the  calciferous 
sandstone  is  derived  from  the  researches  of  Mr.  Logan  in  Canada, 
and  the  study  by  Mr.  Salter  of  the  fossils  collected  by  the  Cana- 
dian Surveyor  near  the  S.  E.  end  of  the  Ottawa  River,  where  one 
mass  of  limestone  incloses  species  common  to  all  the  beds  from 
the  Calciferous  Sandstone  (No.  18.)  up  to  the  Trenton  Limestone 
(No.  14.).  In  this  rock,  the  Asaphus  gigas  and  other  well-known 
Trenton  species  are  blended  with  the  Maclurea  (a  left-handed 
Euomphalus,  fig.  606.),  a  genus  characteristic  of  the  Chazy  Lime- 

Fossflsfrom  Allumctte  Rapids,  River  Ottawa,  Canada. 
a  Fig.  606. 


Maclurea  Logani,  Salter. 
a.  view  of  the  shell.  b.  its  curious  operculum. 

Fig- 607.  stone,   or    No.  17;    and   Murchisonia    gracilis 

(fig.  607.)  is  another  Trenton  Limestone  species 
found   in   the   same  Silurian  limestone  of  Ca- 
nada f;  while  one  of  the  most  common   shells 
in   it   is   the   Raphistoma?  (Euomphalus)  uni- 
angulatum,    Hall,    a    species    characteristic    in 
New  York  of  the  Calciferous  Sandstone  itself. 
is,  Haii.       In  Canada,  as  in  the  State  of  New  York,  the 
A  foss.ii  characteristic  of  Potsdam    Sandstone   underlies   the   above-men- 

the  Trenton  Limestone.  .. 

The  genus  is  common  in   tioned  calcareous  rocks,  but  contains  a  different 

Lower  Silurian  rocks.  .  or*.-,  *n    i.       i.  c>  1-1 

suite  of  fossils,  as  will  be  hereafter  explained. 
In  parts  of  the  globe  still  more  remote  from  Europe  the  Silurian 
strata  have  also  been  recognized,  as  in  South  America,  Australia, 
and  recently  by  Captain  Strachey  in  India,  In  all  these  regions  the 
facies  of  the  fauna,  or  the  types  of  organic  life,  enable  us  to  recognize 
the  contemporaneous  origin  of  the  rocks ;  but  the  fossil  species  are 
distinct,  showing  that  the  old  notion  of  a  universal  diffusion 
throughout  the  "  primaeval  seas  "  of  one  uniform  specific  fauna  was 

*  Hall ;  Forster  and  Whitney's  Report         f  Logan,  Keport,  Brit.  Assoc.  Ipswich, 
on  Lake  Superior.  Ft.  II.  1851.  pp.  59.  63. 


CH.  XXVIT.]  CAMBRIAN   GROUP.  451 

quite  unfounded,  geographical  provinces  having  evidently  existed  in 
the  oldest  as  in  the  most  modern  times.* 

Whether  the  Silurian  rocks  are  of  deep-water  origin.  —  The 
grounds  relied  upon  by  Professor  E.  Forbes  for  inferring  that  the 
larger  part  of  the  Silurian  Fauna  is  indicative  of  a  sea  more  than  70 
fathoms  deep,  are  the  following :  first,  the  small  size  of  the  greater 
number  of  conchifera ;  secondly,  the  paucity  of  pectinibranchiata  (or 
spiral  univalves) ;  thirdly,  the  great  number  of  floaters,  such  as 
Bellerophon,  Orthoceras,  &c. ;  fourthly,  the  abundance  of  orthidiform 
brachiopoda ;  fifthly,  the  absence  or  great  rarity  of  fossil  fish. 

It  is  doubtless  true  that  some  living  Terebratulce,  on  the  coast  of 
Australia,  inhabit  shallow  water ;  but  all  the  known  species,  allied 
in  form  to  the  extinct  Orthis,  inhabit  the  depths  of  the  sea.  It 
should  also  be  remarked  that  Mr.  Forbes,  in  advocating  these  views, 
was  well  aware  of  the  existence  of  shores,  bounding  the  Silurian  sea 
in  Shropshire,  and  of  the  occurrence  of  littoral  species  of  this  early 
date  in  the  northern  hemisphere.  Such  facts  are  not  inconsistent 
with  his  theory ;  for  he  has  shown,  in  another  work,  how,  on  the 
coast  of  Lycia,  deep  sea  strata  are  at  present  forming  in  the  Medi- 
terranean, in  the  vicinity  of  high  and  steep  land. 

Had  we  discovered  the  ancient  delta  of  some  large  Silurian 
river,  we  should  doubtless  have  known  more  of  the  shallow-water, 
brackish-water,  and  fluviatile  animals,  and  of  the  terrestrial  flora  of 
the  period  under  consideration.  To  assume  that  there  were  no  such 
deltas  in  the  Silurian  world,  would  be  almost  as  gratuitous  an 
hypothesis,  as  for  the  inhabitants  of  the  coral  islands  of  the  Pacific 
to  indulge  in  a  similar  generalization  respecting  the  actual  condition 
of  the  globe. 

CAMBRIAN   GROUP. 

Upper  Cambrian.  —  We  have  next  to  consider  the  fossiliferous 
strata  that  occupy  a  lower  position  than  the  "Llandeilo  beds," 
which  last  form,  as  we  have  seen,  the  Lower  division  of  the  great 
Silurian  series,  as  originally  defined  by  Sir  R.  Murchison.  In 
the  Appendix  to  his  important  work  before  cited  f,  Sir  Roderick 
has  given,  on  the  authority  of  Mr.  Salter,  a  list  of  no  less  than 
96  species  of  fossils  (of  which  specimens  have  been  examined 
either  by  himself  or  Prof.  McCoy),  all  common  to  the  Upper  and 
Lower  Silurian  strata,  or,  in  other  words,  which,  being  found 
either  in  the  Ludlow  or  Wenlock  beds,  are  also  met  with  in  the 
Llandeilo  formation.  The  range  upwards  of  so  many  species  from 
the  inferior  to  the  superior  group  shows  that,  independently  of 
the  link  supplied  by  the  Caradoc  or  Middle  Silurian,  there  is  such 
a  connection  between  the  two  principal  divisions,  as  makes  it 
natural  to  assign  the  whole  to  one  great  period.  To  attempt,  there- 
fore, to  give  a  new  name  to  the  Llandeilo  beds,  or  to  call  them 
Cambrian,  as  has  been  recently  proposed  by  some  geologists,  would 

*  E.  Forbes,  Anniv.  Address,  1854.         f  Siluria,  p.  485. 
Quart.  Journ.  Geol.  Soc.,  vol.  x.  p.  38. 

GG  2 


452 


LINGULA   FLAGS   OF    NORTH   WALES.       [Cn.  XXVII. 


be  to  act  in  violation  of  the  ordinary  rules  of  classification,  and 
would  create  much  confusion,  by  disturbing  a  nomenclature  long  re- 
ceived and  originally  established  on  well-defined  paleontological  data. 
In  Shropshire,  the  classical  region,  where  the  type  of  the  Silurian 
group  was  first  made  out  by  Murchison,  the  formations  subjacent  to 
the  Llandeilo  consisted  of  quartzose  rocks,  sterile  of  fossils,  or 
yielding  little  more  than  some  obscure  fucoids.  In  North  Wales, 
Professor  Sedgwick  found  below  the  Bala  Limestone,  long  since 
recognized  as  the  equivalent  of  the  Llandeilo  flags,  a  vast  thickness 
of  sedimentary  and  volcanic  rocks,  the  lithological  characters  and 
physical  features  of  which  he  studied  assiduously  for  years,  dividing 
them  into  well-marked  formations,  to  which  he  affixed  names. 
Collectively  they  constituted  the  chief  part  of  the  rocks  called  by 
him  "  Cambrian."  They  were  devoid  of  limestone ;  but  in  a  group 
of  micaceous  sandstones  Mr.  E.  Davis  discovered  in  1846  the  Lin- 
gula  named  after  him,  and  from  which  the  name  of  "  Lingula  flags  " 
has  since  been  derived.  In  these  flags,  about  1500  or  2000  feet  in 
thickness,  several  other  fossils  were  afterwards  found,  of  different 
species  from  those  in  the  Llandeilo  beds.  Amongst  them,  trilobites, 
Agnostus  and  Conocephalus  (for  genus,  see  fig.  614.),  and  some  rare 
Brachiopoda  and  Bryozoa,  still  unpublished  by  our  Government 
surveyors,  have  been  detected,  and  in  the  inferior  black  slates  of 
North  Wales  a  trilobite  called  Paradoxides  (for  genus,  see  fig.  613.), 
a  form  still  more  characteristic  of  this  era,  together  with  another  of 
the  genus  Olenus  (fig.  610.),  and  a  phyllopod  crustacean  (fig.  608.X 

Fossils  of  the  "  Lingula  Flags"  or  lowest  Fossiliferous  Rocks  of  Britain. 
Fig.  608.  Fig.  609.  Fig.  610. 


Humenocaris  vermtcauda, 

Salter. 

A  Phyllopod  Crustacean. 
^  nat.  size. 

"  Lingula  Flags  "  of  Dolgelly,  and  Ffestiniog  ;  N.Wales. 


Lingula  Davisti,  M'Coy. 

a.  %  natural  size. 

b.  distorted  by  cleavage. 


Olenus  micrurus, 

Salter. 
i  nat.  size. 


I  have  before  observed,  that  between  the  Bala  Limestone  and  the 
Lingula  Flags  there  is  a  thickness  of  11,000  feet  of  strata,  in  which 
Graptolites  and  certain  species  of  Asaphus,  Calymene,  and  Ogygia 
occur.  These  may  be  referred  at  present  to  the  Silurian  series,  but 
the  exact  limits  between  them  and  the  Lingula  Flags  cannot  yet  be 
assigned. 

We  might  have  anticipated,  as  already  remarked,  p.  446.,  that, 
whenever  a  fossil  Fauna  was  discovered  in  the  Cambrian  strata,  it 
would  be  found  to  consist  of  distinct  species,  and  even,  to  a  large 
extent,  of  distinct  genera;  for,  although  geological  periods  are  of 
very  unequal  value  in  regard  to  the  lapse  of  time  (see  p.  104.),  and 


CH.  XXVII.]  LOWER    CAMBRIAN.  453 

our  lines  of  separation  may  often  be  somewhat  arbitrary,  yet  in  no 
part  of  the  world  have  we  hitherto  examined  a  succession  of  rocks 
having  so  great  a  thickness  as  45,000  feet,  even  where  they  are  made 
up  in  part  of  volcanic  materials,  which  have  been  referred  to  one 
period  as  being  characterized  by  one  and  the  same  fauna. 

The  first  formation  mentioned  by  Prof.  Sedgwick,  beneath  the  Bala 
Limestone  (and  its  associated  beds  of  sandstone)  in  N.  Wales,  are 
certain  beds,  7000  feet  thick,  called  the  Arenig  slates  and  porphyry. 
Under  them  he  finds  the  Tremadoc  Slates,  1000  feet  thick,  and  next 
the  Lingula  Flags,  already  described,  1500  feet  or  more,  which,  in 
accordance  with  views  first  put  forward  by  Mr.  Salter,  I  have 
referred  provisionally  to  an  Upper  Cambrian  group. 

Lower  Cambrian.  —  To  the  Lingula  Flags  last  enumerated,  another 
series,  called  by  Prof.  Sedgwick  the  Bangor  Group,  succeeds  in  the 
descending  order,  comprising,  1st,  the  Harlech  Grits,  500  feet  thick, 
and  next  the  Llanberis  Slates,  1000  feet.  These  formations  have 
as  yet  proved  barren  of  organic  remains  in  N.  Wales  ;  but  in  Ireland, 
immediately  opposite  Anglesea  and  Caernarvon,  rocks  of  the  same 
mineral  character  as  the  Bangor  Group,  and  occupying  precisely  the 
same  place  in  the  geological  series,  have  afforded  two  species  of 
zoophytes,  to  which  Professor  Forbes  has  given  the  name  of  Oldhamia 
(figs.  611  and  612.).  The  position  of  these  rocks  has  been  decided 

The  most  Ancient  Fossils  yet  known  (1854). 

Fig.  612. 


Fig.  611, 


Oldhamia  radiata,  Forbes. 
Wicklow,  Ireland. 


Oldhamia  antiqua,  Forbes. 
Wicklow,  Ireland. 

by  the  Government  Surveyors,  and  confirmed  by  Sir  R.  Murchison, 
so  that  here  we  behold  the  relics  of  the  most  ancient  organic  bodies 
yet  known.  We  are  of  course  unable  at  present  to  determine 
whether  they  belong  to  the  same  fauna  as  the  fossils  of  the  "Lin- 
gula Flags,"  or  to  an  older  one.  The  beds  containing  them  may 
provisionally  be  called  Lower  Cambrian,  for  it  will  always  happen 
that  our  inquiries  will  terminate  downwards  in  rocks  affording  very 
imperfect  materials  for  classification.  This  will  continue  to  be  the 
case,  however  many  steps  we  may  make  in  future  in  penetrating 
into  the  remoter  annals  of  the  past. 

G  G  3 


454 


PRIMORDIAL    GROUP   OF    BOHEMIA.       [Cn.  XXVII. 


Bohemia. — M.  Barrande,  in  his  admirable  monograph  on  the  Pa- 
leozoic rocks  of  Bohemia,  has  laid  much  stress  on  the  distinctness 
and  isolation  of  what  he  calls  the  "  Protozoic  schists,"  which  attain 
a  thickness  of  1200  feet,  and  lie  at  the  base  of  the  whole  Silurian 
group,  as  defined  by  him.  These  schists  have  no  limestone  associated 
with  them,  and  are  regarded  by  M.  Barrande  as  contemporaneous 
with  the  "Lingula  Flags"  of  N.  Wales.  So  far  as  he  has  yet 
carried  his  researches,  this  "  primordial  fauna,"  as  he  designates  it, 
has  yielded  scarcely  any  other  fossils  than  Trilobites,  the  other 
animal  remains  consisting  of  a  Pteropod,  some  Cystidese,  and  an 
Or  this,  all  of  new  and  peculiar  species.  Of  the  Trilobites,  even  the 
genera,  with  the  exception  of  one  (Agnostus,  figs.  615  and  616.),  are 
peculiar.  These  genera  are  Paradoxides  (see  fig.  613.),  of  which 
there  are  no  less  than  twelve  species,  Conocephalus  (fig.  614.),  Ellip- 

Fossils  of  the  lowest  Fossiliferous  Sects  in  Bohemia,  or  "  Primordial  Zone  "  of  Barrande. 
Fig.  613.  Fig.  614. 


Conocephalus  slriatus,  Emmrich. 

|  nut.  size. 
Ginetz  and  Skrey. 


Paradoxides  Bohemicus,  Barr. 
About  one  third  natural  size. 


Lowest    Silurian  beds" 

Ginetz,  Bohemia. 
(Etage  C.  of  Barrande.) 


of 


Fig.  615. 


Agnostus  integer,  Beyrich. 
Nat.  size  and  magnified. 


Fig.  616. 


Agnostus  Rex,  Barr. 
Nat.  size,  Skrey. 


socephalus,  Sao  (fig.  617.),  Arionellus, 
and  Hydrocephalus.  They  have  all  a 
facies  of  their  own,  dependent  on  the 
multiplication  of  their  thoracic  seg- 
ments, and  the  diminution  of  their 
caudal  shield  or  pygidium. 

All   the  Bohemian  species  differ  as 
Sao  hirsuta,  Barrande,  in  its  various  yet  from  any  found  in  England,  which 
Th,  £T£,*Cit&ii  the  may  be  owing  chiefly  to  the  very  small 
true  size,   in  the  youngest  state  a,  number  as  yet  known  in  Great  Britain  ; 

no  segments  are  visible ;  as  the  meta-  <f 

morphosis  progresses,  b,  c,  the  body  or  ft   may  fee    due    entirely  tO   the    influ- 

segments  begin  to  be  developed  ;  in  •  .*  . 

the  stage  d  the  eyes  are  introduced,  enC6    OI    geographical    CaUSCS       It    SCemS 

but  the  facial  sutures  are  not  com-  °  _  ,  .  , 

pieted ;  at  e  the  full-grown  animal,  nevertheless  to  confirm  the  view  here 
taken,  of  the  «  primordial  zone"  being 

characterized  by  fossils  distinguishable  from  the  Llandeilo,  or 
Lower  Silurian  group;  because  the  other  and  higher  Silurian  for- 
mations of  Barrande  have  each  of  them  many  species  in  common 
with  the  successive  subdivisions  of  the  British  series. 


POTSDAM    SANDSTONE    OF    N.  AMERICA.  455 

One  of  the  so-called  "  primordial "  Trilobites  of  the  genus  Sao, 
a  form  not  found  as  yet  elsewhere  in  the  world,  lias  afforded  M.  Bar- 
rande  a  fine  illustration  of  the  metamorphosis  of  these  creatures ; 
for  he  has  traced  them  through  no  less  than  twenty  stages  of  their 
development.  A  few  of  these  changes  have  been  selected  for  repre- 
sentation in  the  accompanying  figures,  that  the  reader  may  learn  the 
gradual  manner  in  which  different  segments  of  the  body  and  the  eyes 
make  their  appearance.  When  we  reflect  on  the  altered  and  crys- 
talline condition  usually  belonging  to  rocks  of  this  age,  and  how 
devoid  of  life  they  are  for  the  most  part  in  North  Wales,  Ireland, 
and  Shropshire,  the  information  respecting  such  minute  details  of 
the  Natural  History  of  these  crustaceans,  as  is  supplied  by  the  Bo- 
hemian strata,  may  well  excite  our  astonishment,  and  may  reasonably 
lead  us  to  indulge  a  hope  that  geologists  may  one  day  gain  an  insight 
into  the  condition  of  the  planet  and  its  inhabitants  at  eras  long  an- 
tecedent to  the  Cambrian ;  for  those  parts  of  the  globe  which  have 
been  subjected  to  a  scrutiny  as  rigorous  as  North  Wales  and  Bohemia 
are  insignificant  spots,  and  we  are  every  day  discovering  new  areas, 
especially  in  the  United  States  and  Canada,  where  beds  as  old  as  the 
"  primordial  schists,"  or  older,  may  be  studied. 

Sweden  and  Norway.  —  The  Lingula  Flags  of  North  Wales,  and 
the  "  primordial  schists "  of  Bohemia,  are  represented  in  Sweden  by 
strata,  the  fossils  of  which  have  been  described  by  an  able  naturalist, 
M.  Angelin,  in  his  " Palseontologica  Suecica  (1852-4)."  The  "alum 
schists,"  as  they  are  called  in  Sweden,  resting  on  a  fucoid-sandstone, 
contain  trilobites  belonging  to  the  genera  Paradoxides,  Olenus, 
Agnostus,  and  others,  some  of  which  present  rudimentary  forms,  like 
the  genus  last  mentioned,  without  eyes,  and  with  the  body  seg- 
ments scarcely  developed,  and  others  again  have  the  number  of  seg- 
ments excessively  multiplied,  as  in  Paradoxides.  These  peculiarities 
agree  with  the  characters  of  the  crustaceans  met  with  in  the  Upper 
Cambrian  strata,  before  mentioned. 

United  States  and  Canada. — In  the  table,  at  p.  448.,  I  have 
already  pointed  out  the  relative  position  of  the  Potsdam  Sandstone, 
which  has  long  been  known  as  the  lowest  fossiliferous  formation  in 
the  United  States  and  Canada.  I  have  seen  it  on  the  banks  of  the 
St.  Lawrence  in  Canada,  and  on  the  borders  of  Lake  Champlain, 
where,  as  at  Keesville,  it  is  a  white  quartzose  fine-grained  grit, 
almost  passing  into  quartzite.  It  is  divided  into  horizontal  ripple- 
marked  beds,  very  like  those  of  the  Lingula  flags  of  Britain,  and 
replete  with  a  small  round-shaped  Lingula  in  such  numbers  as  to 
divide  the  rock  into  parallel  planes,  in  the  same  manner  as  do  the 
scales  of  mica  in  some  micaceous  sandstones.  This  formation,  as  we 
learn  from  Mr.  Logan,  is  700  feet  thick  in  Canada ;  the  lower  portion 
consisting  of  a  conglomerate  with  quartz  pebbles ;  the  upper  part  of 
sandstone  containing  fucoids,  and  perforated  by  small  vertical  holes, 
which  are  very  characteristic  of  the  rock,  and  appear  to  have  been 
made  by  annelids  (Scolithus  linearis). 

On  the  banks  of  the  St.  Lawrence,  near  Beauharnois  and  else- 

G  G  4 


456  FOOTPRINTS   NEAR    MONTREAL.  [Cn.  XXVII. 

where,  many  fossil  footprints  have  been  observed  on  the  surface  of 
its  rippled  layers.  These  impressions  were  first  noticed  by  Mr. 
Abraham,  of  Montreal,  in  1847,  and  were  supposed  to  be  tracks  of  a 
tortoise ;  but  Mr.  Logan  has  since  brought  some  of  the  slabs  to 
London,  together  with  numerous  casts  of  other  slabs,  enabling  Pro- 
fessor Owen  to  correct  the  idea  first  entertained,  and  to  decide  that 
they  were  not  due  to  a  chelonian,  nor,  as  he  imagines,  to  any  vertebrate 
creature.  The  Hunterian  Professor  inclines  to  the  belief  that  they 
are  the  trails  of  more  than  one  species  of  articulate  animal,  probably 
allied  to  the  King  Crab,  or  Limulus.  Between  the  two  rows  of 
foot-tracks  runs  an  impressed  median  line  or  channel,  supposed  by 
the  Professor  to  have  been  made  by  a  caudal  appendage  rather  than 
by  a  prominent  part  of  the  trunk.  Some  individuals  appear  to  have 
had  three,  and  others  five  pairs,  of  limbs  used  for  locomotion.  The 
width  of  the  tracks  between  the  outermost  impressions  varies  from  3£ 
to  5J  inches,  which  would  imply  a  creature  of  much  larger  dimen- 
sions than  any  organic  body  yet  obtained  from  strata  of  such  an- 
tiquity. Their  size  alone  is  therefore  important,  as  warning  us  of  the 
danger  of  drawing  any  inference,  from  mere  negative  evidence, 
as  to  the  extreme  poverty  of  the  fauna  of  the  earlier  seas. 

Mr.  Logan  informs  us  *,  that  the  Lower  Silurian  strata  and  the 
Potsdam  Sandstone  in  Canada  rest  unconformably  on  a  still  older 
series  of  aqueous  rocks,  which,  as  he  says,  may  be  Cambrian  (Lower 
Cambrian,  or,  perhaps,  still  older  ?),  and  which  include  conglomerates 
and  beds  of  limestone.  In  both  of  these,  nodules  of  phosphate  of  lime 
are  frequently  observed.  That  these  contorted  rocks  are  of  aqueous 
origin,  he  infers  from  the  presence  of  quartz  pebbles  in  the  conglo- 
merates. Together  with  the  associated  igneous  masses,  this  ancient 
series  attains  a  thickness  of  at  least  10,000  feet,  in  the  Lake  Huron 
district,  and  includes  the  copper-bearing  rocks  of  that  part  of  Canada. 
Below  these  again  lies  gneiss,  with  interstratified  marble,  in  which 
crystals  of  phosphate  of  lime  both  large  and  small  are  not  uncommon. 
This  phosphate,  as  Mr.  Logan  suggests,  may  have  "  a  possible  con- 
nection with  life  in  those  ancient  rocks." 

In  the  frontispiece  to  this  volume,  and  in  fig.  83.  p.  59.,  the  reader 
may  refer  to  a  section  on  the  coast  of  Scotland  where  the  Devonian 
strata  lie  unconformably  on  the  highly  inclined  Silurian  schists,  and 
I  have  cited  the  eloquent  reflections  of  Playfair  when  he  looked,  with 
his  teacher  Hutton,  "  so  far  into  the  abyss  of  time."  But  in  the  lake 
district  of  N.  America,  the  Potsdam  Sandstone,  forming  the  upper  or 
horizontal  series,  is  older  than  even  the  inclined  strata  of  St.  Abb's 
Head  in  Scotland.  In  Canada  again,  we  behold  the  monuments  of 
still  another  period  in  the  remote  distance,  attesting,  as  Playfair 
exclaimed,  "  how  much  farther  the  reason  may  go  than  the  imagina- 
tion can  venture  to  follow." 

Valley  of  the  Upper  Mississippi.  —  Mr.  Dale  Owen  has  recently 
published  a  graphic  sketch,  in  his  survey  of  Wisconsin  (1852),  of 
the  lowest  sedimentary  rocks  near  the  head-waters  of  the  Mississippi, 

*  Quart.  Geol.  Journ.,  vol.  viii.  p.  210. 


Cu.  XXVII.]      PERIOD    OF    INVERTEBRATE    ANIMALS.  457 

lying  at  the  base  of  the  whole  Silurian  series.     They  are  many 
Fig  618  hundred  feet  thick,  and  for  the  most  part 

similar  in  character  to  the  Potsdam  Sandstone 
above  described,  but  including  in  their  upper 
portions  intercalated  bands  of  magnesian 
limestone,  and  in  'their  lower  some  argilla- 
ceous beds.  Among  the  shells  of  these  strata 
are  species  ofLingtila  &nd.0rthis,  and  several 
trilobites  of  the  new  genus  Dikelocephalus 
(fig.  618.).  These  rocks,  occurring  in  Iowa, 
Wisconsin,  and  Minnesota,  seem  destined 
hereafter  to  throw  great  light  on  the  state 
of  organic  life  in  the  Cambrian  period.  Six 
beds  containing  trilobites,  separated  by  strata 
iMocephaius  Minnesotensis,  from  10  to  150  feet  thick,  are  already  enu- 

Dale  Owen.    £  diameter.  » 


A  large  crustacean  of  the  Olenoid 
group.        Potsdam      Sandstone.          T>   i    >•  ./•       o»'?       •  in        i     • 

Fails  of  st.  croix,  on  the  upper      Relation     of    Silurian     and    Cambrian 
18Slppl'  Faunas.  —  That  there  is  a  considerable  con- 

nection between  the  Cambrian  and  Lower  Silurian  faunas,  not- 
withstanding that  nearly  every  species  may  be  distinct,  seems  evident  ; 
but  it  may  not  be  a  closer  one  than  that  existing  between  the  Upper 
Silurian  and  Devonian.  This  I  infer  from  the  following  facts,  —  that  in 
Bohemia,  where  the  Cambrian  or  primordial  fauna  of  Barrande  is  best 
developed,  it  consists  mainly  of  Trilobites  ;  and  of  this  order  more 
than  two  thirds  of  the  genera  and  all  the  species,  more  than  twenty  in 
number,  are,  with  one  exception  (Agnostus  pisiformis),  distinct  from 
the  Silurian.  But  M.  Barrande  observes  that  out  of  thirty-nine 
Silurian  genera  of  Trilobites,  no  less  than  eleven  pass  upwards  into 
the  Devonian.  If,  therefore,  we  had  only  trilobites  in  the  latter,  its 
generic  relationship  to  the  Silurian  fauna  would  appear  greater  than 
that  of  the  Silurian  to  the  Cambrian.  And,  though  the  details  of 
the  English  rocks  of  this  age  are  not  yet  fully  known,  the  species  at 
least  appear  all  to  be  distinct.  The  same  holds  good  with  regard  to 
the  fossils  of  the  Swedish  strata,  and,  as  we  have  seen,  to  those  of 
America. 

A  distinctive  character,  therefore,  is  given  to  the  fauna  of  this 
period,  by  which  we  seem  to  be  carried  one  step  further  back  into 
the  history  of  organic  life. 

Supposed  Period  of  Invertebrate  Animals. 

We  have  seen  that  in  the  upper  part  of  the  Silurian  system  a 
bone-bed  occurs  near  Ludlow,  in  which  the  remains  of  fish  are  abun- 
dant, and  amongst  them  some  of  a  highly  organized  structure,  referred 
to  the  genus  Onchus.  We  are  indebted  to  Sir  R.  Murchison  for 
having  first  announced,  in  1840,  the  discovery  of  these  ichthyolites, 
and  he  then  spoke  of  them  as  "the  most  ancient  beings  of  their 
class."  In  his  new  and  excellent  work,  entitled  "  Siluria  "  (p.  239.), 
he  reverts  to  the  opinion  formerly  expressed  by  him,  and  observes 


458  UPPER   SILURIAN    BONE-BED.  [Cn.  XXVII. 

that  the  active  researches  of  the  last  fourteen  years  in  Europe  and 
America  "  have  failed  to  modify  that  generalization,"  adding  "  the 
Silurian  system,  therefore,  may  be  regarded  as  representing  a  long 
early  period,  in  which  no  vertebrated  animals  had  been  called  into 
existence." 

It  is  certainly  a  fact  well  worthy  of  our  attention,  that  as  yet  no 
remains  of  fish  are  on  record  as  coming  from  any  stratum  older  than 
the  base  of  the  "  Upper  Ludlow."  (See  above,  p.  436.)  When  we  re- 
flect on  the  number  of  Mollusks,  Echinoderms,  Corals,  Trilobites, 
and  other  fossils  already  obtained  from  Silurian  strata  below  "  the 
Ludlow,"  we  may  well  ask,  whether  any  other  set  of  fossiliferous 
formations  were  ever  studied  with  equal  diligence  and  over  so  vast 
an  area  without  yielding  some  ichthyolites. 

Nevertheless,  we  must  be  permitted  to  hesitate  before  we  accept, 
even  on  such  evidence,  so  sweeping  a  conclusion,  as  that  the  globe, 
for  ages  after  it  was  habitable  by  all  the  great  classes  of  inverte- 
brata,  remained  wholly  untenanted  by  vetebrate  animals.  In  the  first 
place,  we  must  remember  that  we  have  detected  no  insects,  or  land- 
shells,  or  freshwater  pulmoniferous  mollusks,  or  terrestrial  crus- 
taceans, or  plants  (except  fucoids),  in  rocks  below  the  Upper 
Silurian.  Their  absence  may  admit  of  explanation,  by  supposing  all 
the  deposits  of  that  era  hitherto  examined  to  have  been  formed  in 
seas  far  from  land  or  beyond  the  influence  of  rivers.  Here  and 
there  indeed  a  shallow -water,  or  even  a  littoral  deposit  may  have 
been  met  with,  as  in  North  Wales,  for  example,  and  North  America  ; 
but,  speaking  generally,  the  Silurian  deposits,  as  at  present  known, 
have  certainly  a  more  pelagic  character  than  any  other  equally  im- 
portant formations. 

It  is  a  curious  fact,  and  not  perhaps  a  mere  fortuitous  coincidence, 
that  the  only  stratum  which  has  yielded  the  remains  of  land- 
plants  is  also  the  only  one  which  has  afforded  the  bones  of  fish. 
Bone-beds  in  general,  such  as  that  of  the  Lias  near  Bristol,  those  of 
the  Trias  near  Stuttgardt,  of  the  Carboniferous  Limestone  near 
Bristol  and  Armagh,  and  lastly  that  of  the  "  Upper  Ludlow,"  are 
remarkable  for  containing  teeth  and  bones,  much  rolled  and  im- 
plying transportation  from  a  distance.  The  association  of  the  spores 
of  Lycopodiacese  (see  p.  436.)  with  the  Ludlow  fish-bones  shows  that 
plants  had  been  washed  from  some  dry  land,  then  existing,  and  had 
been  drifted  into  a  common  submarine  receptacle  with  the  bones. 
More  usually,  however,  the  "  Upper  Ludlow,"  like  the  "  Lower 
Silurian,"  is  devoid  of  plants  and  equally  destitute  of  ichthyolites. 

It  has  been  suggested  that  Cephalopoda  were  so  abundant  in  the 
Silurian  period  that  they  may  have  discharged  the  functions  of  fish  ; 
to  which  we  may  reply  that  both  classes  coexisted  in  the  Upper  Silu- 
rian period,  and  both  of  them  swarmed  together  in  the  Carboniferous 
and  Liassic  seas,  as  they  do  now  in  certain  parts  of  the  ocean.  We 
may  also  suggest  that  we  are  too  imperfectly  acquainted  with  the 
distribution  of  scattered  bones  and  teeth  or  the  skeletons  of  dead 
fish  on  the  floor  of  the  existing  ocean,  to  have  a  right  to  theorise 


CH.  XXVII.]      ABSENCE    OF   FISH    IN   LOWER    SILURIAN.         459 

with  confidence  on  the  absence  of  such  relics  over  wide  spaces  at 
former  eras. 

They  who  in  our  own  times  have  explored  the  bed  of  the  sea  inform 
us  that  it  is  in  general  as  barren  of  vertebrate  remains  as  the  soil  of 
a  forest  on  which  thousands  of  mammalia  and  reptiles  may  have 
flourished  for  centuries.  In  the  summer  of  1850,  Prof.  E.  Forbes 
and  Mr.  McAndrew  dredged  the  bed  of  the  British  seas  from  the  Isle 
of  Portland  to  the  Land's  End  in  Cornwall,  and  thence  again  to  Shet- 
land, recording  and  tabulating  the  numbers  of  the  various  organic 
bodies  brought  up  by  them  in  the  course  of  140  distinct  dredgings, 
made  at  different  distances  from  the  shore,  some  a  quarter  of  a  mile, 
others  forty  miles  distant.  The  list  of  species  of  marine  invertebrate 
animals,  whether  Radiata,  Mollusca,  or  Articulata,  was  very  great, 
and  the  number  of  individuals  enormous ;  but  the  only  instances  of 
vertebrate  animals  consisted  of  a  few  ear-bones  and  two  or  three 
vertebrae  of  fish,  in  all  not  above  six  relics. 

It  is  still  more  extraordinary  that  Mr.  McAndrew  should  have 
dredged  the  great  "Ling  Banks"  or  cod-fishery  grounds  off  the 
Shetland  Islands  for  shells  without  obtaining  the  bones  or  teeth  of 
any  dead  fish,  although  he  sometimes  drew  up  live  fish  from  the 
mud.  This  is  the  more  singular,  because  there  are  some  areas  where 
recent  fish-bones  occur  in  the  same  northern  seas  in  profusion,  as  I 
have  shown  in  the  "  Principles  of  Geology  "  (see  Index,  "  Vidal ") ; 
two  bone-beds  having  been  discovered  by  British  hydrographers,  one 
in  the  Irish  sea,  and  the  other  in  the  sea  near  the  Faroe  Isles,  the  first 
of  them  two,  and  the  other  three  and  a  half  miles  in  length,  where 
the  lead  brings  up  everywhere  the  vertebrae  of  fish  from  various 
depths  between  45  to  235  fathoms.  These  may  be  compared  to  the 
Upper  Ludlow  bone-bed ;  and  on  the  floor  of  the  ocean  of  our  times, 
as  on  that  of  the  Silurian  epoch,  there  are  other  wide  spaces  where 
no  bones  are  imbedded  in  mud  or  sand. 

It  may  be  true,  though  it  sounds  somewhat  like  a  paradox,  that 
fish  leave  behind  them  no  memorials  of  their  presence  in  places 
where  they  swarm  and  multiply  freely  ;  whereas  currents  may  drift 
their  bones  in  great  numbers  to  regions  wholly  destitute  of  living 
fish.  Such  a  state  of  things  would  be  quite  analogous  to  what 
takes  place  on  the  habitable  land,  where,  instead  of  the  surface 
becoming  encumbered  with  heaps  of  skeletons  of  quadrupeds, 
birds,  and  land-reptiles,  all  solid  bony  substances  are  removed  after 
death  by  chemical  processes,  or  by  the  digestive  powers  of  pre- 
daceous  beasts  ;  so  that,  if  at  some  future  period  a  geologist  should 
seek  for  monuments  of  the  former  existence  of  such  creatures,  he 
must  look  anywhere  rather  than  in  the  area  where  they  flourished. 
He  must  search  for  them  in  spots  which  were  covered  at  the  time 
with  water,  and  to  which  some  bones  or  carcases  may  have  been 
occasionally  carried  by  floods  and  permanently  buried  in  sediment. 

In  the  annexed  Table,  a  few  dates  are  set  before  the  reader  of  the 
discovery  of  different  classes  of  animals  in  ancient  rocks,  to  enable 
him  to  perceive  at  a  glance  how  gradual  has  been  our  progress  in 


460      PROGRESSIVE    DISCOVERY    OF    VERTEBRATA     [Cn.  XXVII. 

tracing  back  the  signs  of  Vertebrata  to  formations  of  high  antiquity. 
Such  facts  may  be  useful  in  warning  us  not  to  assume  too  hastily 
that  the  point  which  our  retrospect  may  have  reached  at  the  present 
moment  can  be  regarded  as  fixing  the  date  of  the  first  introduction 
of  any  one  class  of  beings  upon  the  earth. 

Dates  of  the  Discovery  of  different  Classes  of  Fossil  Vertebrata ; 
showing  the  gradual  Progress  made  in  tracing  them  to  Rocks  of 
higher  Antiquity. 

Year.  Formations. 

1798.     Middle  Eocene  (or  B.  i.  p.  223.). 


Mammalia. 


Aves. 


Beptilia. 


Pisces. 


1818.  Lower  Oolite. 

1847.  Upper  Trias. 

1 782.  Middle  Eocene  (or  B.  i.  p.  223.). 

1839.  Lower  Eocene. 

C171Q.  Permian  (or  Zechstein). 

<  1844.  Carboniferous. 

[l852.  Upper  Devonian. 

1709.  Permian  (or  Kupfer-schiefer). 

1 7 93.  Carboniferous  (Mountain  Lime- 
stone). 

1828.  Devonian. 

1840.  Upper  Silurian. 


Geographical  Localities. 
Paris    (Gypsum    of 

Montmartre).1 
Stonesfield.2 
Stuttgardt.3 

Paris    (Gypsum    of 

Montmartre).4 
London     (Sheppey 

Clay).5 

Thuringia.6 

Saarbruck,nearTreves.7 

Elgin.8 

Thuringia.9 
Glasgow. lo 

Caithness.11 
Ludlow.12 


1  Cuvier  (George).    Bulletin  Soc.  Philom.  xx.     Scattered  bones  were  found  in 
the  gypsum  some  years  before  ;  but  they  were  determined  osteologically,  and 
their  true  geological  position  was  assigned  to  them  in  this  memoir. 

2  In  1818,  Cuvier,  visiting  the  Museum  of  Oxford,  decided  on  the  mammalian 
character  of  a  jaw  from  Stonesfield.     See  also  above,  p.  312. 

3  Plieninger,  Prof.     See  above,  p.  342. 

4  M.  Darcet  discovered,  and  Lamanon  figured,  as  a  fossil  bird,  some  remains 
from  Montmartre,  afterwards  recognized  as  such  by  Cuvier  (  Ossemens  Foss.,  Art. 
*'  Oiseaux  "). 

5  Owen,  Prof.,  Geol.  Trans.  2nd  Ser.  vol.  vi.  p.  203.,  1839.     The  fossil  bird  dis- 
covered in  the  same  year  in  the  slates  of  Glaris  in  the  Alps,  and  at  first  referred 
to  the  chalk,  is  now  supposed  to  belong  to  the  Nummulitic  beds,  and  may  there- 
fore be  of  newer  date  than  the  Sheppey  Clay. 

6  The  fossil  monitor  of  Thuringia  (Protorosaurus  Speneri,  V.  Meyer)  was  figured 
by  Spener,  of  Berlin,  in  1810.  (Miscel.  Berlin.) 

7  See  above,  p.  401. 

8  See  above,  p.  416. 

9  Memorabilia  Saxonise  Subterr.,  Leipsic,  1709. 

w  History  of  Eutherglen,  by  Rev.  David  Ure,  1793. 

11  Sedgwick  and  Murchison,  Geol.  Trans.,  2nd  Ser.  vol.  iii.  p.  141.,  1828. 

12  Sir  R.  Murchison.     See  above,  p.  435. 

Obs.  The  evidence  derived  from  footprints,  though  often  to  be  relied  on,  is  omit- 
ted in  the  above  table,  as  being  less  exact  than  that  founded  on  bones  and  teeth. 

How  many  living  writers  are  there  who,  before  the  year  1844, 
generalized  fearlessly  on  the  non-existence  of  reptiles  before  the 
Permian  era  !  Yet,  in  the  course  of  ten  years,  they  have  lived  to  see 
the  earliest  known  date  of  the  creation  of  reptiles  carried  back  suc- 
cessively, first  to  the  Carboniferous,  and  then  to  the  Upper  Devonian 
periods.  Before  the  year  1818,  it  was  the  popular  belief  that  the 
Palseotherium  of  the  Paris  gypsum  and  its  associates  were  the  first 
warm-blooded  quadrupeds  that  ever  trod  the  surface  of  this  planet. 


CH.  XXVII.]  IN   OLDER   ROCKS.  461 

So  fixed  was  this  idea  in  the  minds  of  the  majority  of  naturalists, 
that,  when  at  length  the  Stonesfield  Mammalia  awoke  from  a  slumber 
of  three  or  four  great  periods,  the  apparition  failed  to  make  them 
renounce  their  creed. 

"  Unwilling  I  my  lips  unclose — 
Leave,  oh,  leave  me  to  repose." 

First,  the  antiquity  of  the  rock  was  called  in  question ;  and  then 
the  mammalian  character  of  the  relics.  Even  long  after  all  contro- 
versy was  set  at  rest  on  these  points,  the  real  import  of  the  new 
revelation,  as  bearing  on  the  doctrine  of  progressive  development, 
was  far  from  being  duly  appreciated. 

It  is  clear  that  the  first  two  or  three  species,  encountered  in  any 
country  or  in  the  rocks  of  any  epoch,  cannot  be  taken  as  a  type  or 
standard  for  measuring  the  grade  of  organization  of  any  terrestrial 
fauna,  ancient  or  modern.  Suppose  that  the  two  or  three  oolitic 
species  first  brought  to  light  had  really  been  all  marsupial,  as  was  for 
a  time  erroneously  imagined,  this  would  not  have  borne  out  the 
inference  which  some  attempted  to  deduce  from  it,  namely,  that  the 
time  had  not  yet  come  for  the  creation  of  the  placental  tribes.  Or, 
if  when  some  monodelph  were  at  last  actually  recognized  (at  Stones- 
field),  they  happened  to  be  of  diminutive  size,  and  to  belong  to  the 
insectivora,  we  are  not  entitled  to  deduce  from  such  data  that  the 
oolitic  fauna  ranked  low  in  the  general  scale,  as  the  insectivora  may 
do  in  an  existing  fauna.  The  real  significance  of  the  discoveries 
alluded  to  arises  from  the  aid  they  afford  us  in  estimating  the  true 
value  of  negative  evidence,  when  brought  to  bear  on  certain  specu- 
lative questions.  Every  zoologist  will  admit  that  between  the  first 
creation  and  the  final  extinction  of  any  one  of  the  five*  oolitic 
mammalia  now  known  there  were  many  successive  generations ;  and, 
if  the  geographical  range  of  each  species  was  limited  (which  we 
have  no  right  to  assume),  still  there  must  have  been  several  hun- 
dred individuals  in  each  generation,  and  probably,  when  the  species 
reached  its  maximum,  several  thousands.  When,  therefore,  we  en- 
counter for  the  first  time  in  1854  two  or  three  jaws  of  a  Spalacothe- 
rium  in  the  Purbeck  limestone,  after  countless  specimens  of  Mollusca 
and  Crustacea,  and  hundreds  of  insects,  fish,  and  reptiles  had  been 
previously  collected  from  the  same  beds,  we  are  not  simply  taught  that 
these  individual  quadrupeds  flourished  at  the  era  in  question,  but  that 
thousands,  perhaps  hundreds  of  thousands,  of  the  same  species  peopled 
the  land  without  leaving  behind  them  any  trace  of  their  existence, 
whether  in  the  shape  of  fossil  bones  or  footprints ;  or,  if  they  left 
any  traces,  these  have  eluded  a  long  and  most  persevering  search. 

Moreover,  we  must  never  forget  how  many  of  the  dates  given  in  the 

*  I  had  written  four,  but  while  this  Stereognathus  ooliticus.  It  is  more  than 
sheet  was  passing  through  the  press  twice  the  size  of  any  of  the  species  pre- 
(Sept.  26, 18  54)  the  disco  very  of  another  viously  obtained  from  the  same  forma- 
species  of  insectivorous  mammal  from  tion.  We  have  now,  therefore,  including 
Stonesfield  was  announced  to  the  British  the  recently  found  Spalacotherium  of 
Association  at  Liverpool  by  Mr.  Charles-  Purbeck  (see  p.  296. ),  five  British  mam- 
worth,  who  has  given  to  it  the  name  of  malia  from  the  oolite. 


462  VERTEBRATA   IN   THE  [Cn.  XXVII. 

above  table  (p.  460.),  are  due  to  British  skill  and  energy,  Great  Britain 
being  still  the  only  country  in  which  mammalia  have  been  found  in 
Oolitic  rocks ;  the  only  region  where  any  reptiles  have  been  detected 
in  strata  as  old  as  the  Devonian  ;  the  only  one  wherein  the  bones  of 
birds  have  been  traced  back  as  far  as  the  London  Clay.  And,  if 
geology  had  been  cultivated  with  less  zeal  in  our  island,  we  should 
know  nothing  as  yet  of  two  extensive  assemblages  of  tertiary  mam- 
malia of  higher  antiquity  than  the  fauna  of  the  Paris  Gypsum 
(already  cited  as  having  once  laid  claim  to  be  the  earliest  that  ever 
flourished  on  the  earth) — namely,  first,  that  of  the  Headon  series 
(see  above,  p.  213.);  and,  secondly,  one  long  prior  to  it  in  date,  and 
antecedent  to  the  London  Clay.*  This  last  has  already  afforded  us 
indications  of  Quadrumana,  Cheiroptera,  Pachydermata,  and  Mar- 
supialia  (see  p.  218.).  How  then  can  we  doubt,  if  every  area  on  the 
globe  were  to  be  studied  with  the  same  diligence,  —  if  all  Europe, 
Asia,  Africa,  America,  and  Australia  were  equally  well  known,  that 
every  date  assigned  by  us  in  the  above  Table  for  the  earliest  re- 
corded appearance  of  fish,  reptiles,  birds,  and  mammals  would  have 
to  be  altered  ?  Nay,  if  one  other  area,  such  as  part  of  Spain,  of  the 
size  of  England  and  Scotland,  were  subjected  to  the  same  scrutiny 
(and  we  are  still  very  imperfectly  acquainted  even  with  Great 
Britain),  each  class  of  Vertebrata  would  probably  recede  one  or 
more  steps  farther  back  into  the  abyss  of  time :  fish  might  penetrate 
into  the  Lower  Silurian, — reptiles  into  the  Lower  Devonian, — 
mammalia  into  the  Lower  Trias, — birds  into  the  Chalk  or  Oolite, — 
and,  if  we  turn  to  the  Invertebrata,  Trilobites  and  Cephalopods 
might  descend  into  the  Lower  Cambrian, — and  some  stray  zoophyte, 
like  the  Oldhamia,  into  rocks  now  styled  "  azoic." 

Yet,  after  these  and  many  more  analogous  revisions  of  the  Table, 
it  might  still  be  just  as  easy  as  now  to  found  a  theory  of  progressive 
development  on  the  new  set  of  positive  and  negative  facts  thus 
established ;  for  the  order  of  chronological  succession  in  the  different 
classes  of  fossil  animals  would  probably  continue  the  same  as  now ;  — 
in  other  words,  our  success  in  tracing  back  the  remains  of  each  class 
to  remote  eras  would  be  greatest  in  fishes,  next  in  reptiles,  next  in 
mammalia,  and  least  in  birds.  That  we  should  meet  with  ichthy- 
olites  more  universally  at  each  era,  and  at  greater  depths  in  the 
series,  than  any  other  class  of  fossil  vertebrata,  would  follow  partly 
from  our  having  as  paleontologists  to  do  chiefly  with  strata  of 
marine  origin,  and  partly,  because  bones  of  fish,  "however  partial  and 
capricious  their  distribution  on  the  bed  of  the  sea,  are  nevertheless 
more  easily  met  with  than  those  of  reptiles  or  mammalia.  In  like 
manner,  the  extreme  rarity  of  birds  in  recent  and  Pliocene  strata, 
even  in  those  of  freshwater  origin,  might  lead  us  to  anticipate  that 
their  remains  would  be  obtained  with  the  greatest  difficulty  in  the 
older  rocks,  as  the  Table  proves  to  be  the  case, — even  in  tertiary 

*  A  bird's  bone  is  recorded  as  having  (beneath  the  London  clay),  by  Mr.Prest- 
been  lately  found  in  the  Woolwich  beds  wich  ;  Geol.  Quart.  Journ.  vol.x.p.  157. 


CH.  XXVII.]         OLDER   FOSSILIFEROUS   PERIODS.  463 

strata,  wherein  we  can  more  readily  find  deposits  formed  in  lakes 
and  estuaries. 

The  only  incongruity  between  the  geological  results,  and  those 
which  our  dredging  experiences  might  have  led  us  to  anticipate 
a  priori,  consists  in  the  frequency  of  fossil  reptiles,  and  the  com- 
parative scarcity  of  mammalia.  It  would  appear  that  during  all  the 
secondary  periods,  not  even  excepting  the  newest  part  of  the  cre- 
taceous, there  was  a  greater  development  of  reptile  life  than  is  now 
witnessed  in  any  part  of  the  globe.  The  preponderance  of  this 
class  over  the  mammalia  depended  probably  on  climatal  and  geo- 
graphical conditions,  for  we  can  scarcely  refer  it  to  "progressive 
development,"  by  which  the  vertebrate  type  was  steadily  improving, 
or  becoming  more  perfect,  as  Time  rolled  on.  We  cannot  shut  our 
eyes  to  the  positive  proofs  now  obtained  of  the  creation  of  mammalia 
before  the  excess  of  reptiles  had  ceased, — nay,  apparently  before  it 
had  even  reached  its  maximum. 

In  conclusion,  I  shall  simply  express  my  own  conviction  that  we 
are  still  on  the  mere  threshold  of  our  inquiries  ;  and  that,  as  in  the 
last  fifty  years,  so  in  the  next  half-century,  we  shall  be  called  upon 
repeatedly  to  modify  our  first  opinions  respecting  the  range  in  time 
of  the  various  classes  of  fossil  Vertebrata.  It  would  therefore  be 
premature  to  generalize  at  present  on  the  non-existence,  or  even  on 
the  scarcity  of  Yertebrata,  whether  terrestrial  or  aquatic,  at  periods 
of  high  antiquity,  such  as  the  Silurian  and  Cambrian.* 

*  For  observations  on  the  rarity  of  air-breathers  in  the  coal,  see  above,  p.  405. 


464  TRAP  ROCKS.  [Cn.  XXVIII, 


CHAPTER 

VOLCANIC   ROCKS. 

Trap  rocks  — Name,  whence  derived — Their  igneous  origin  at  first  doubted — 
Their  general  appearance  and  character  —  Volcanic  cones  and  craters,  how 
formed — Mineral  composition  and  texture  of  volcanic  rocks  —  Varieties  of 
felspar  —  Hornblende  and  augite — Isomorphism  —  Rocks,  how  to  be  studied — 
Basalt,  trachyte,  greenstone,  porphyry,  scoria,  amygdaloid,  lava,  tuff  —  Agglo- 
merate— Laterite — Alphabetical  list,  and  explanation  of  names  and  synonyms,  of 
volcanic  rocks  —  Table  of  the  analyses  of  minerals  most  abundant  in  the  vol- 
canic and  hypogene  rocks. 

THE  aqueous  or  fossiliferous  rocks  having  now  been  described,  we 
have  next  to  examine  those  which  may  be  called  volcanic,  in  the 
most  extended  sense  of  that  term.  Suppose  a  a  in  the  annexed 

Fig.  619. 


a.  Hypogene  formations,  stratified  and  unstratified. 

b.  Aqueous  formations.  c.  Volcanic  rocks. 

diagram,  to  represent  the  crystalline  formations,  such  as  the  granitic 
and  metamorphic  ;  b  b  the  fossiliferous  strata ;  and  c  c  the  volcanic 
rocks.  These  last  are  sometimes  found,  as  was  explained  in  the  first 
chapter,  breaking  through  a  and  b,  sometimes  overlying  both,  and 
occasionally  alternating  with  the  strata  b  b.  They  also  are  seen,  in 
some  instances,  to  pass  insensibly  into  the  unstratified  division  of  #, 
or  the  Plutonic  rocks. 

When  geologists  first  began  to  examine  attentively  the  structure 
of  the  northern  and  western  parts  of  Europe,  they  were  almost  en- 
tirely ignorant  of  the  phenomena  of  existing  volcanos.  They  found 
certain  rocks,  for  the  most  part  without  stratification,  and  of  a 
peculiar  mineral  composition,  to  which  they  gave  different  names, 
such  as  basalt,  greenstone,  porphyry,  and  amygdaloid.  All  these, 
which  were  recognized  as  belonging  to  one  family,  were  called  "  trap  " 
by  Bergmann,  from  trappa,  Swedish  for  a  flight  of  steps  —  a  name 
since  adopted  very  generally  into  the  nomenclature  of  the  science  ; 
for  it  was  observed  that  many  rocks  of  this  class  occurred  in  great 
tabular  masses  of  unequal  extent,  so  as  to  form  a  succession  of  ter- 
races or  steps  on  the  sides  of  hills.  This  configuration  appears  to 
be  derived  from  two  causes.  First,  the  abrupt  original  terminations 
of  sheets  of  melted  matter,  which  have  spread,  whether  on  the  land 
or  bottom  of  the  sea,  over  a  level  surface.  For  we  know,  in  the 
case  of  lava  flowing  from  a  volcano,  that  a  stream,  when  it  has 


CH;  XXVIII.]  CONES   AND   CRATERS.  465 

ceased  to  flow,  and  grown  solid,  very  commonly  ends  in  a  steep  slope, 
as  at  «,  fig.  620.  But,  secondly,  the  step-like  appearance  arises 
more  frequently  from  the  mode  in  which 
horizontal  masses  of  igneous  rock,  such 
as  b  c,  intercalated  between  aqueous 
strata,  or  showers  of  volcanic  dust  and 
ashes,  have,  subsequently  to  their  origin, 
been  exposed,  at  different  heights,  by 
denudation.  Such  an  outline,  it  is  true, 
is  not  peculiar  to  trap  rocks ;  great  beds 
step-like  appearance  of  trap.  of  iimestone,  and  other  hard  kinds  of 
stone,  often  presenting  similar  terraces  and  precipices :  but  these 
are  usually  on  a  smaller  scale,  or  less  numerous,  than  the  volcanic 
steps,  or  form  less  decided  features  in  the  landscape,  as  being  less 
distinct  in  structure  and  composition  from  the  associated  rocks. 

Although  the  characters  of  trap  rocks  are  greatly  diversified,  the 
beginner  will  easily  learn  to  distinguish  them  as  a  class  from  the 
aqueous  formations.  Sometimes  they  present  themselves,  as  already 
stated,  in  tabular  masses,  which  are  not  divided  by  horizontal  planes 
of  stratification  in  the  manner  of  sedimentary  deposits.  Sometimes 
they  form  chains  of  hills  often  conical  in  shape.  Not  unfrequently 
they  are  seen  as  "  dikes "  or  wall-like  masses,  intersecting  fossili- 
ferous  beds.  The  rock  is  occasionally  columnar,  the  columns  some- 
times decomposing  into  balls  of  various  sizes,  from  a  few  inches  to 
several  feet  in  diameter.  The  decomposing  surface  very  commonly 
assumes  a  coating  of  a  rusty  iron  colour,  from  the  oxidation  of  ferru- 
ginous matter,  so  abundant  in  the  traps  in  which  augite  or  horn- 
blende occur;  or,  in  the  felspathic  varieties  of  trap,  it  acquires  a 
white  opaque  coating,  from  the  bleaching  of  the  mineral  called  fel- 
spar. On  examining  any  of  these  volcanic  rocks,  where  they  have 
not  suffered  disintegration,  we  rarely  fail  to  detect  a  crystalline 
arrangement  in  one  or  more  of  the  component  minerals.  Sometimes 
the  texture  of  the  mass  is  cellular  or  porous,  or  we  perceive  that  it 
has  once  been  full  of  pores  and  cells,  which  have  afterwards  become 
filled  with  carbonate  of  lime,  or  other  infiltrated  mineral. 

Most  of  the  volcanic  rocks  produce  a  fertile  soil  by  their  disinte- 
gration. It  seems  that  their  component  ingredients,  silica,  alumina, 
lime,  potash,  iron,  and  the  rest,  are  in  proportions  well  fitted  for 
the  growth  of  vegetation.  As  they  do  not  effervesce  with  acids,  a 
deficiency  of  calcareous  matter  might  at  first  be  suspected ;  but 
although  the  carbonate  of  lime  is  rare,  except  in  the  nodules  of 
amygdaloids,  yet  it  will  be  seen  that  lime  sometimes  enters  largely 
into  the  composition  of  augite  and  hornblende.  (See  Table,  p.  479.) 
Cones  and  Craters. — In  regions  where  the  eruption  of  volcanic 
matter  has  taken  place  in  the  open  air,  and  where  the  surface  has 
never  since  been  subjected  to  great  aqueous  denudation,  cones  and 
craters  constitute  the  most  striking  peculiarity  of  this  class  of  form- 
ations. Many  hundreds  of  these  cones  are  seen  in  central  France, 
in  the  ancient  provinces  of  Auvergne,  Velay,  and  Vivarais,  where 

H  H 


466 


COMPOSITION   AND   NOMENCLATURE      [Cn.  XXVIII. 


they  observe,  for  the  most  part,  a  linear  arrangement,  and  form 
chains  of  hills.  Although  none  of  the  eruptions  have  happened 
within  the  historical  era,  the  streams  of  lava  may  still  be  traced  dis- 
tinctly descending  from  many  of  the  craters,  and  following  the  lowest 
levels  of  the  existing  valleys.  The  origin  of  the  cone  and  crater- 


rig.  621. 


Part  of  the  chain  of  extinct  volcanos  called  the  Monts  Dome,  Auvergne.    (Scrope.) 

shaped  hill  is  well  understood,  the  growth  of  many  having  been 
watched  during  volcanic  eruptions.  A  chasm  or  fissure  first  opens 
in  the  earth,  from  which  great  volumes  of  steam  and  other  gases  are 
evolved.  The  explosions  are  so  violent  as  to  hurl  up  into  the  air 
fragments  of  broken  stone,  parts  of  which  are  shivered  into  minute 
atoms.  At  the  same  time  melted  stone  or  lava  usually  ascends  through 
the  chimney  or  vent  by  which  the  gases  make  their  escape.  Although 
extremely  heavy,  this  lava  is  forced  up  by  the  expansive  power  of 
entangled  gaseous  fluids,  chiefly  steam  or  aqueous  vapour,  exactly  in 
the  same  manner  as  water  is  made  to  boil  over  the  edge  of  a  vessel 
when  steam  has  been  generated  at  the  bottom  by  heat.  Large 
quantities  of  the  lava  are  also  shot  up  into  the  air,  where  it  separates 
into  fragments,  and  acquires  a  spongy  texture  by  the  sudden  enlarge- 
ment of  the  included  gases,  and  thus  forms  scorice,  other  portions 
being  reduced  to  an  impalpable  powder  or  dust.  The  showering 
down  of  the  various  ejected  materials  round  the  orifice  of  eruption 
gives  rise  to  a  conical  mound,  in  which  the  successive  envelopes  of 
sand  and  scoria  form  layers,  dipping  on  all  sides  from  a  central  axis. 
In  the  mean  time  a  hollow,  called  a  crater,  has  been  kept  open  in 
the  middle  of  the  mound  by  the  continued  passage  upwards  of  steam 
and  other  gaseous  fluids.  The  lava  sometimes  flows  over  the  edge  of 
the  crater,  and  thus  thickens  and  strengthens  the  sides  of  the  cone ; 
but  sometimes  it  breaks  down  the  cone  on  one  side  (see  fig.  621.), 
and  often  it  flows  out  from  a  fissure  at  the  base  of  the  hill,  or  at 
some  distance  from  its  base.* 

Composition  and  nomenclature. — Before  speaking  of  the  connection 
between  the  products  of  modern  volcanos  and  the  rocks  usually  styled 
trappean,  and  before  describing  the  external  forms  of  both,  and  the 
manner  and  position  in  which  they  occur  in  the  earth's  crust,  it  will 
be  desirable  to  treat  of  their  mineral  composition  and  names.  The 
varieties  most  frequently  spoken  of  are  basalt  and  trachyte,  to  which 

*  For  a  description  and  theory  of  active  volcanos,  see  Principles  of  Geology, 
chaps,  xxiv.  et  seq.  &  xxxii. 


CH.  XXVIII.]  OF   VOLCANIC   KOCKS.  487 

dolerite,  greenstone,  clinkstone,  and  others  might  be  added;  while 
those  founded  chiefly  on  peculiarities  of  texture,  are  porphyry, 
amygdaloid,  lava,  volcanic  breccia  or  agglomerate,  tuff,  scoriae,  and 
pumice.  It  may  be  stated  generally,  that  all  these  are  mainly  com- 
posed of  two  minerals,  or  families  of  simple  minerals,  felspar  and 
hornblende;  but  the  felspar  preponderates  greatly  even  in  those 
rocks  to  which  the  hornblendic  mineral  imparts  its  distinctive  cha- 
racter and  prevailing  colour. 

The  two  minerals  alluded  to  may  be  regarded  as  two  groups,  rather 
than  species.  Felspar,  for  example,  may  be,  first,  common  felspar 
(often  called  Orthoclase),  that  is  to  say,  potash-felspar,  in  which  the 
predominant  alkali  is  potash  (see  Table,  p.  479.) ;  or,  secondly,  albite, 
that  is  to  say,  soda-felspar,  where  the  predominant  alkali  is  soda 
instead  of  potash ;  or,  thirdly,  Oligoclase ;  or,  fourthly,  Labrador- 
felspar  (Labradorite),  which  differs  not  only  in  its  iridescent  hues, 
but  also  in  its  angle  of  fracture  or  cleavage,  and  its  composition. 
We  also  read  much  of  two  other  kinds,  called  glassy  felspar  and 
compact  felspar,  which,  however,  cannot  rank  as  varieties  of  equal 
importance,  for  both  the  albitic  and  common  felspar  appear  some- 
times in  transparent  or  glassy  crystals  ;  and  as  to  compact  felspar,  it 
is  a  compound  of  a  less  definite  nature,  sometimes  containing  largely 
both  soda  and  potash  ;  and  which  might  be  called  a  felspathic  paste, 
being  the  residuary  matter  after  portions  of  the  original  matrix  have 
crystallized.  The  more  recent  •  analyses  have  shown  that  all  the 
varieties  or  species  of  felspar  may  contain  both  potash  and  soda, 
although  in  some  of  them  the  one,  and  in  others  the  other  alkali 
greatly  prevails. 

The  hornblendic  group  consists  principally  of  two  varieties ;  first, 
hornblende,  and,  secondly,  augite,  which  were  once  regarded  as 
very  distinct,  although  now  some  eminent  mineralogists  are  in  doubt 
whether  they  are  not  one  and  the  same  mineral,  differing  only  as  one 
crystalline  form  of  native  sulphur  differs  from  another. 

The  history  of  the  changes  of  opinion  on  this  point  is  curious  and 
instructive.  Werner  first  distinguished  augite  from  hornblende ;  and 
his  proposal  to  separate  them  obtained  afterwards  the  sanction  of 
Haiiy,  Mohs,  and  other  celebrated  mineralogists.  It  was  agreed  that 
the  form  of  the  crystals  of  the  two  species  were  different,  and  their 
structure,  as  shown  by  cleavage,  that  is  to  say,  by  breaking  or  cleaving 
the  mineral  with  a  chisel,  or  a  blow  of  the  hammer,  in  the  direction 
in  which  it  yields  most  readily.  It  was  also  found  by  analysis  that 
augite  usually  contained  more  lime,  less  alumina,  and  no  fluoric  acid ; 
which  last,  though  not  always  found  in  hornblende,  often  enters  into 
its  composition  in  minute  quantity.  In  addition  to  these  characters, 
it  was  remarked  as  a  geological  fact,  that  augite  and  hornblende  are 
very  rarely  associated  together  in  the  same  rock  ;  and  that  when  this 
happened,  as  in  some  lavas  of  modern  date,  the  hornblende  occurs  in 
the  mass  of  the  rock,  where  crystallization  may  have  taken  place  more 
slowly,  while  the  augite  merely  lines  cavities  where  the  crystals  may 
have  been  produced  rapidly.  It  was  also  remarked,  that  in  the 

H  H    2 


468  THEORY   OF   ISOMORPHISM.  [Cn.  XXVIII. 

crystalline  slags  of  furnaces,  augitic  forms  were  frequent,  the  horn- 
blendic  entirely  absent ;  hence  it  was  conjectured  that  hornblende 
might  be  the  result  of  slow,  and  augite  of  rapid  cooling.  This  view 
was  confirmed  by  the  fact,  that  Mitscherlich  and  Berthier  were  able 
to  make  augite  artificially,  but  could  never  succeed  in  forming  horn- 
blende. Lastly,  Gustavus  Rose  fused  a  mass  of  hornblende  in  a 
porcelain  furnace,  and  found  that  it  did  not,  on  cooling,  assume 
its  previous  shape,  but  invariably  took  that  of  augite.  The  same 
mineralogist  observed  certain  crystals  in  rocks  from  Siberia  which 
presented  a  hornblende  cleavage,  while  they  had  the  external  form 
of  augite. 

If,  from  these  data,  it  is  inferred  that  the  same  substance  may 
assume  the  crystalline  forms  of  hornblende  or  augite  indifferently, 
according  to  the  more  or  less  rapid  cooling  of  the  melted  mass,  it  is 
nevertheless  certain  that  the  variety  commonly  called  augite,  and 
recognised  by  a  peculiar  crystalline  form,  has  usually  more  lime  in  it, 
and  less  alumina,  than  that  called  hornblende,  although  the  quantities 
of  these  elements  do  not  seem  to  be  always  the  same.  Unquestionably 
the  facts  and  experiments  above  mentioned  show  the  very  near 
affinity  of  hornblende  and  augite ;  but  even  the  convertibility  of  one 
into  the  other,  by  melting  and  recrystallizing,  does  not  perhaps  de- 
monstrate their  absolute  identity.  For  there  is  often  some  portion 
of  the  materials  in  a  crystal  which  are  not  in  perfect  chemical  com- 
bination with  the  rest.  Carbonate  of  lime,  for  example,  sometimes 
carries  with  it  a  considerable  quantity  of  silex  into  its  own  form 
of  crystal,  the  silex  being  mechanically  mixed  as  sand,  and  yet  not 
preventing  the  carbonate  of  lime  from  assuming  the  form  proper  to 
it.  This  is  an  extreme  case,  but  in  many  others  some  one  or  more 
of  the  ingredients  in  a  crystal  may  be  excluded  from  perfect  chemical 
union ;  and  after  fusion,  when  the  mass  recrystallizes,  the  same 
elements  may  combine  perfectly  or  in  new  proportions,  and  thus  a 
new  mineral  may  be  produced.  Or  some  one  of  the  gaseous  elements 
of  the  atmosphere,  the  oxygen  for  example,  may,  when  the  melted 
matter  reconsolidates,  combine  with  some  one  of  the  component 
elements. 

The  different  quantity  of  the  impurities  or  refuse  above  alluded  to, 
which  may  occur  in  all  but  the  most  transparent  and  perfect  crystals, 
may  partly  explain  the  discordant  results  at  which  experienced 
chemists  have  arrived  in  their  analysis  of  the  same  mineral.  For  the 
reader  will  find  that  crystals  of  a  mineral  determined  to  be  the  same 
by  physical  characters,  crystalline  form,  and  optical  properties,  have 
often  been  declared  by  skilful  analyzers  to  be  composed  of  distinct  ele- 
ments. (See  the  table  at  p.  479.)  This  disagreement  seemed  at  first 
subversive  of  the  atomic  theory,  or  the  doctrine  that  there  is  a  fixed 
and  constant  relation  between  the  crystalline  form  and  structure  of 
a  mineral  and  its  chemical  composition.  The  apparent  anomaly, 
however,  which  threatened  to  throw  the  whole  science  of  mineralogy 
into  confusion,  was  in  a  great  degree  reconciled  to  fixed  principles 
by  the  discoveries  of  Professor  Mitscherlich  at  Berlin,  who  ascertained 


CH.:XXVIII.]  PYROXENE  —  AMPHIBOLE.  469 

that  the  composition  of  the  minerals  which  had  appeared  so  variable, 
was  governed  by  a  general  law,  to  which  he  gave  the  name  of 
isomorphism  (from  t<rog,  isos,  equal,  and  poptyr],  morphe,  form).  Ac- 
cording to  this  law,  the  ingredients  of  a  given  species  of  mineral  are 
not  absolutely  fixed  as  to  their  kind  and  quality  ;  but  one  ingredient 
may  be  replaced  by  an  equivalent  portion  of  some  analogous  ingre- 
dient. Thus,  in  augite,  the  lime  may  be  in  part  replaced  by  portions 
of  protoxide  of  iron,  or  of  manganese,  while  the  form  of  the  crystal, 
and  the  angle  of  its  cleavage  planes,  remain  the  same.  These 
vicarious  substitutions,  however,  of  particular  elements  cannot  exceed 
certain  defined  limits. 

Pyroxene,  a  name  of  Haiiy's,  is  often  used  for  augite  in  descrip- 
tions of  volcanic  rocks.  It  is  properly,  according  to  M.  Delesse,  a 
general  name,  under  which  Augite,  Diallage,  and  Hypersthene  may 
be  united,  for  these  three  are  varieties  of  one  and  the  same  mineral 
species,  having  the  same  chemical  formula  with  variable  bases. 

Amphibole  is  in  like  manner  a  general  term  under  which  Horn- 
blende and  Actinolite  may  be  united. 

Having  been  led  into  this  digression  on  some  recent  steps  made  in 
the  progress  of  mineralogy,  I  may  here  observe  that  the  geological 
student  must  endeavour  as  soon  as  possible  to  familiarize  himself 
with  the  characters  of  five  at  least  of  the  most  abundant  simple 
minerals  of  which  rocks  are  composed.  These  are  felspar,  quartz, 
mica,  hornblende,  and  carbonate  of  lime.  This  knowledge  cannot 
be  acquired  from  books,  but  requires  personal  inspection,  and  the 
aid  of  a  teacher.  It  is  well  to  accustom  the  eye  to  know  the  appear- 
ance of  rocks  under  the  lens.  To  learn  to  distinguish  felspar  from 
quartz  is  the  most  important  step  to  be  first  aimed  at.  In  general 
we  may  know  the  felspar  because  it  can  be  scratched  with  the  point 
of  a  knife,  whereas  the  quartz,  from  its  extreme  hardness,  receives 
no  impression.  But  when  these  two  minerals  occur  in  a  granular 
and  uncrystallized  state,  the  young  geologist  must  not  be  discouraged 
if,  after  considerable  practice,  he  often  fails  to  distinguish  them  by 
the  eye  alone.  If  the  felspar  is  in  crystals,  it  is  easily  recognized  by 
its  cleavage ;  but  when  in  grains  the  blow-pipe  must  be  used,  for 
the  edges  of  -the  grains  can  be  rounded  in  the  flame,  whereas  those 
of  quartz  are  infusible.  If  the  geologist  is  desirous  of  detecting  the 
varieties  of  felspar  above  enumerated,  or  distinguishing  hornblende 
from  augite,  it  will  often  be  necessary  to  use  the  reflecting  gonio- 
meter as  a  test  of  the  angle  of  cleavage,  and  shape  of  the  crystal. 
The  use  of  this  instrument  will  not  be  found  difficult. 

The  external  characters  and  composition  of  the  felspars  are  ex- 
tremely different  from  those  of  augite  or  hornblende ;  so  that  the  vol- 
canic rocks  in  which  either  of  these  minerals  play  a  conspicuous  part 
are  easily  recognizable.  But  there  are  mixtures  of  the  two  elements 
in  very  different  proportions,  the  mass  being  sometimes  exclusively 
composed  of  felspar,  and  at  other  times  largely  of  augite.  Between 
the  two  extremes  there  is  almost  every  intermediate  gradation ;  yet 
certain  compounds  prevail  so  extensively  in  nature,  and  preserve  so 

H  II  3 


470  BASALT  —  AUGITE  —  TRACHYTE.         [Cn.  XXVIII. 

much  uniformity  of  aspect  and  composition,  that  it  is  useful  in 
geology  to  regard  them  as  distinct  rocks,  and  to  assign  names  to 
them,  such  as  basalt,  greenstone,  trachyte,  and  others  presently  to 
be  mentioned. 

Basalt.  —  As  an  example  of  rocks  in  which  augite  is  a  conspicuous 
ingredient,  basalt  may  first  be  mentioned.  Although  we  are  more 
familiar  with  this  term  than  with  that  of  any  other  kind  of  trap,  it 
is  difficult  to  define  it,  the  name  having  been  used  so  compre- 
hensively, and  sometimes  so  vaguely.  It  has  been  generally  applied 
to  any  trap  rock  of  a  black,  bluish,  or  leaden-grey  colour,  having  a 
uniform  and  compact  texture.  Most  strictly,  it  consists  of  an  inti- 
mate mixture  of  felspar,  augite,  and  iron,  to  which  a  mineral  of  an 
olive-green  colour,  called  olivine,  is  often  superadded,  in  distinct 
grains  or  nodular  masses.  The  iron  is  usually  magnetic,  and  is  often 
accompanied  by  another  metal,  titanium.  The  term  "  Dolerite  "  is 
now  much  used  for  this  rock,  when  the  felspar  is  of  the  variety  called 
Labradorite,  as  in  the  lavas  of  Etna.  Basalt,  according  to  Dr.  Dau- 
beny,  in  its  more  strict  sense,  is  composed  of  "  an  intimate  mixture 
of  augite  with  a  zeolitic  mineral  which  appears  to  have  been  formed 
out  of  Labradorite  by  the  addition  of  water,  the  presence  of  water 
being  in  all  zeolites  the  cause  of  that  bubbling  up  under  the  blow- 
pipe, to  which  they  owe  their  appellation.*  Of  late  years  the 
analyses  of  M.  Delesse  and  other  eminent  mineralogists  have  shown 
that  the  opinion  once  entertained,  that  augite  was  the  prevailing 
mineral  in  basalt,  or  even  in  the  most  augitic  trap  rocks,  must  be 
abandoned.  Although  its  presence  gives  to  these  rocks  their  dis- 
tinctive character  as  contrasted  with  trachytes,  still  the  principal 
element  in  their  composition  is  felspar. 

Augite  rock  has,  indeed,  been  defined  by  Leonhard  as  being  made 
up  principally  or  wholly  of  augite  f,  and  in  some  veinstones,  says 
Delesse,  such  a  rock  may  be  found ;  but  the  greater  part  of  what 
passes  by  the  name  of  augite  rock  is  more  rich  in  green  felspar 
than  in  augite.  Ampkibotite,  in  like  manner,  or  Hornblende  rock, 
is  a  trap  of  the  basaltic  family,  in  which  there  is  much  hornblende, 
and  in  which  this  mineral  has  been  supposed  to  predominate ;  but 
Delesse  finds,  by  analysis,  that  the  felspar  may  be  in  excess,  the 
base  being  felspathic. 

In  some  varieties  of  basalt  the  quantity  of  olivine  is  very  great ; 
and  as  this  mineral  differs  but  slightly  in  its  chemical  composition 
from  serpentine  (see  Table  of  Analyses,  p.  479.),  containing  even  a 
larger  proportion  of  magnesia  than  serpentine,  it  has  been  suggested 
with  much  probability  that  in  the  course  of  ages  some  basalts  highly 
charged  with  olivine  may  be  turned,  by  metamorphic  action,  into 
serpentine. 

Trachyte.  —  This  name,  derived  from  rpaxvc,  rough,  has  been 
given  to  the  felspathic  class  of  volcanic  rocks  which  have  a  coarse, 
cellular  paste,  rough  and  gritty  to  the  touch.  This  paste  has 
commonly  been  supposed  to  consist  chiefly  of  albite,  but  according 

*  Volcanos,  2d  ed.  p.  18.  f  Mineralreich,  2d  ed.  p.  85. 


Cm-XXVIII.]       TRACHYTE   PORPHYRY  —  CLINKSTONE.  471 

to  M.  Delesse  it  is  variable  in  composition,  its  prevailing  alkali  being 
soda.  Through  the  base  are  disseminated  crystals  of  glassy  felspar, 
mica,  and  sometimes  quartz  and  hornblende,  although  in  the  trachyte, 
properly  so  called,  there  is  no  quartz.  The  varieties  of  felspar  which 
occur  in  trachyte  are  trisilicates,  or  those  in  which  the  silica  is  to 
the  alumina  in  the  proportion  of  three  atoms  to  one.* 

Trachytic  Porphyry,  according  to  Abich,  has  the  ordinary  com- 
position of  trachyte,  with  quartz  superadded,  and  without  any  augite 
or  titaniferous  iron.  Andesite  is  a  name  given  by  Gustavus  Rose  to 
a  trachyte  of  the  Andes,  which  contains  the  felspar  called  Andesin, 
together  with  glassy  felspar  (orthoclase)  and  hornblende  dissemi- 
nated through  a  dark-coloured  base. 

Clinkstone,  or  Pkonolite.  —  Among  the  felspathic  products  of  vol- 
canic action,  this  rock  is  remarkable  for  its  tendency  to  lamination, 
which  is  sometimes  such  that  it  affords  tiles  for  roofing.  It  rings 
when  struck  with  the  hammer,  whence  its  name;  is  compact,  and 
usually  of  a  greyish  blue  or  brownish  colour ;  is  variable  in  compo- 
sition, but  almost  entirely  composed  of  felspar,  and  in  some  cases, 
according  to  Gmelin,  of  felspar  and  mesotype.  When  it  contains 
disseminated  crystals  of  felspar,  it  is  called  Clinkstone  porphyry. 

Greenstone  is  the  most  abundant  of  those  volcanic  rocks  which  are 
intermediate  in  their  composition  between  the  Basalts  and  Trachytes. 
The  name  has  usually  been  extended  to  all  granular  mixtures, 
whether  of  hornblende  and  felspar,  or  of  augite  and  felspar.  The 
term  diorite  has  been  applied  exclusively  to  compounds  of  hornblende 
and  felspar.  According  to  the  analyses  of  Delesse  and  others,  the 
chief  cause  of  the  green  colour,  in  most  greenstones,  is  not  green 
hornblende  nor  augite,  but  a  green  siliceous  base,  very  variable  and 
indefinite  in  its  composition.  The  dark  colour,  however,  of  diorite  is 
usually  derived  from  disseminated  plates  of  hornblende. 

The  Basalts  contain  a  smaller  quantity  of  silica  than  the  Trachytes, 
and  a  larger  proportion  of  lime  and  magnesia.  Hence,  independently 
of  the  frequent  presence  of  iron,  basalt  is  heavier.  Abich  has  there- 
fore proposed  that  we  should  weigh  these  rocks,  in  order  to  appre- 
ciate their  composition  in  cases  where  it  is  impossible  to  separate 
their  component  minerals.  Thus,  the  variety  of  basalt  called  dolerite, 
which  contains  53  per  cent,  of  silica,  has  a  specific  gravity  of  2'86 ; 
whereas  trachyte,  which  has  66  per  cent,  of  silica,  has  a  sp.  gr.  of 
only  2*68 ;  trachytic  porphyry,  containing  69  per  cent,  of  silica,  a 
sp.  gr.  of  only  2'58.  If  we  then  take  a  rock  of  intermediate  compo- 
sition, such  as  that  prevailing  in  the  Peak  of  Teneriffe,  which  Abich 
calls  Trachyte -dolerite,  its  proportion  of  silica  being  intermediate, 
or  58  per  cent.,  it  weighs  2 -78,  or  more  than  trachyte,  and  less  than 
basalt,  f  The  basalts  are  generally  dark  in  colour,  sometimes  almost 
black,  whereas  the  trachytes  are  grey,  and  even  occasionally  white. 
As  compared  with  the  granitic  rocks,  basalts  and  trachytes  contain 
both  of  them  more  soda  in  their  composition,  the  potash-felspars 

*  Dr.  Daubeny  on  Volcanos,  2d  ed.  pp.  14,  15.  f  Ibid. 

H  II  4 


472  PORPHYRY — AMYGDALOID.  [Cn.  XXVIIJ. 

being  generally  abundant  in  the  granites.  The  volcanic  rocks 
moreover,  whether  basaltic  or  trachytic,  contain  less  silica  than  the 
granites,  in  which  last  the  excess  of  silica  has  gone  to  form  quartz. 
This  mineral,  so  conspicuous  in  granite,  is  usually  wanting  in  the 
volcanic  formations,  and  never  predominates  in  them. 

The  fusibility  of  the  igneous  rocks  generally  exceeds  that  of  other 
rocks,  for  the  alkaline  matter  and  lime  which  commonly  abound  in 
their  composition  serve  as  a  flux  to  the  large  quantity  of  silica,  which 
would  be  otherwise  so  refractory  an  ingredient. 

We  may  now  pass  to  the  consideration  of  those  igneous  rocks,  the 
characters  of  which  are  founded  on  their  form  rather  than  their 
composition, 

Porphyry  is  one  of  this  class,  and  very  characteristic  of  the  vol- 
canic formations.  When  distinct  crystals  of  one  or  more  minerals  are 
scattered  through  an  earthy  or  compact  base,  the  rock  is  termed 
a  porphyry  (see  fig.  622.).  Thus  trachyte  is  porphyritic ;  for  in  it, 
as  in  many  modern  lavas,  there  are  crystals  of  felspar ;  but  in  some 
porphyries  the  crystals  are  of  augite,  olivine,  or  other  minerals. 
If  the  base  be  greenstone,  basalt,  or  pitchstone,  the  rock  may  be 
denominated  greenstone-porphyry,  pitchstone-porphyry,  and  so 
forth.  The  old  classical  type  of  this  form  of  rock  is  the  red  por- 
Fig.  622.  phyry  of  Egypt,  or  the  well  known 

"  Rosso  antico."  It  consists,  according 
to  Delesse,  of  a  red  felspathic  base  in 
which  are  disseminated  rose-coloured 
crystals  of  the  felspar  called  oligoclase, 
with  some  plates  of  blackish  horn- 
blende and  grains  of  oxidized  iron-ore 
(fer  oligiste).  Red  quartziferous  por- 
phyry is  a  much  more  siliceous  rock, 
containing  about  70  or  80  per  cent, 
of  silex,  while  that  of  Egypt  has  only 

Porphyry.  62  per  Cent. 

ohnbfeS  Amygdaloid.  —  This   is    also    ano- 

ther form  of  igneous  rock,  admitting 

of  every  variety  of  composition.  It  comprehends  any  rock  in  which 
round  or  almond-shaped  nodules  of  some  mineral,  such  as  agate, 
calcedony,  calcareous  spar,  or  zeolite,  are  scattered  through  a  base  of 
wacke,  basalt,  greenstone,  or  other  kind  of  trap.  It  derives  its  name 
from  the  Greek  word  amygdala,  an  almond.  The  origin  of  this 
structure  cannot  be  doubted,  for  we  may  trace  the  process  of  its 
formation  in  modern  lavas.  Small  pores  or  cells  are  caused  by 
bubbles  of  steam  and  gas  confined  in  the  melted  matter.  After  or 
during  consolidation,  these  empty  spaces  are  gradually  filled  up  by 
matter  separating  from  the  mass,  or  infiltered  by  water  permeating 
the  rock.  As  these  bubbles  have  been  sometimes  lengthened  by  the 
flow  of  the  lava  before  it  finally  cooled,  the  contents  of  such  cavities 
have  the  form  of  almonds.  In  some  of  the  amygdaloidal  traps  of 
Scotland,  where  the  nodules  have  decomposed,  the  empty  cells  are 


C«,  XXVIII.]  LAVA  —  SCORI2E  —  PUMICE.  473 

seen  to  have  a  glazed  or  vitreoys  coating,  and  in  this  respect  exactly 

resemble  scoriaceous  lavas,  or  the  slags  of  furnaces. 

Fi    623  The  annexed  figure  represents  a 

fragment  of  stone  taken  from  the 
upper  part  of  a  sheet  of  basaltic 
lava  in  Auvergne.  One  half  is 
scoriaceous,  the  pores  being  per- 
fectly empty;  the  other  part  is 
amygdaloidal,  the  pores  or  cells 
being  mostly  filled  up  with  car- 
bonate of  lime,  forming  white  ker- 
nels. 

Lava. — This  term  has  a  some- 
what vague  signification,  having 
been  applied  to  all  melted  matter 
observed  to  flow  in  streams  from 

Scoriaceous  lava^part  Converted  into  an        volcamc  VCntS.      When  this  matter 
Montagne  de  la  Veille,  Department  of  Puy       Consolidates    in    the    Open    air,    the 

Dome,  France.  upper  part  is  usually  scoriaceous, 

and  the  mass  becomes  more  and  more  stony  as  we  descend,  or  in 
proportion  as  it  has  consolidated  more  slowly  and  under  greater 
pressure.  At  the  bottom,  however,  of  a  stream  of  lava,  a  small 
portion  of  scoriaceous  rock  very  frequently  occurs,  formed  by  the 
first  thin  sheet  of  liquid  matter,  which  often  precedes  the  main  cur- 
rent, or  in  consequence  of  the  contact  with  water  in  or  upon  the 
damp  soil. 

The  more  compact  lavas  are  often  porphyritic,  but  even  the 
scoriaceous  part  sometimes  contains  imperfect  crystals,  which  have 
been  derived  from  some  older  rocks,  in  which  the  crystals  pre- 
existed, but  were  not  melted,  as  being  more  infusible  in  their 
nature. 

Although  melted  matter  rising  in  a  crater,  and  even  that  which 
enters  a  rent  on  the  side  of  a  crater,  is  called  lava,  yet  this  term 
belongs  more  properly  to  that  which  has  flowed  either  in  the  open 
air  or  on  the  bed  of  a  lake  or  sea.  If  the  same  fluid  has  not  reached 
the  surface,  but  has  been  merely  injected  into  fissures  below  ground, 
it  is  called  trap. 

There  is  every  variety  of  composition  in  lavas  ;  some  are  trachy- 
tic,  as  in  the  Peak  of  Teneriffe ;  a  great  number  are  basaltic,  as  in 
Vesuvius  and  Auvergne ;  others  are  Andesitic,  as  those  of  Chili ; 
some  of  the  most  modern  in  Vesuvius  consist  of  green  augite,  and 
many  of  those  of  Etna  of  augite  and  Labrador-felspar.* 

Scoria  and  Pumice  may  next  be  mentioned  as  porous  rocks,  pro- 
duced by  the  action  of  gases  on  materials  melted  by  volcanic  heat. 
Scoria  are  usually  of  a  reddish-brown  and  black  colour,  and  are  the 
cinders  and  slags  of  basaltic  or  augitic  lavas.  Pumice  is  a  light, 
spongy,  fibrous  substance,  produced  by  the  action  of  gases  on 

*  G.  Rose,  Ann.  des  Mines,  torn.  viii.  p.  32. 


474  VOLCANIC   TUFF — PALAGONITE   TUFF.    [CH.XXVIII. 

trachytic  and  other  lavas  ;  the  relation,  however,  of  its  origin  to  the 
composition  of  lava  is  not  yet  well  understood.  Von  Buch  says  that 
it  never  occurs  where  only  Labrador-felspar  is  present. 

Volcanic  tuff.  Trap  tuff.  —  Small  angular  fragments  of  the  scoria? 
and  pumice,  above-mentioned,  and  the  dust  of  the  same,  produced  by 
volcanic  explosions,  form  the  tuffs  which  abound  in  all  regions  of 
active  volcanos,  where  showers  of  these  materials,  together  with 
small  pieces  of  other  rocks  ejected  from  the  crater,  fall  down  upon 
the  land  or  into  the  sea.  Here  they  often  become  mingled  with 
shells,  and  are  stratified.  Such  tuffs  are  sometimes  bound  together 
by  a  calcareous  cement,  and  form  a  stone  susceptible  of  a  beautiful 
polish.  But  even  when  little  or  no  lime  is  present,  there  is  a  great 
tendency  in  the  materials  of  ordinary  tuffs  to  cohere  together.  Be- 
sides the  peculiarity  of  their  composition,  some  tuffs,  or  volcanic  grifs, 
as  they  have  been  termed,  differ  from  ordinary  sandstones  by  the 
angularity  of  their  grains,  and  they  often  pass  into  volcanic  breccias. 

According  to  Mr.  Scrope,  the  Italian  geologists  confine  the  term 
tuff,  or  tufa,  to  felspathose  mixtures,  and  those  composed  principally 
of  pumice,  using  the  term  peperino  for  the  basaltic  tuffs.*  The 
peperinos  thus  distinguished  are  usually  brown,  and  the  tuffs  grey  or 
white. 

We  meet  occasionally  with  extremely  compact  beds  of  volcanic 
materials,  interstratified  with  fossiliferous  rocks.  These  may  some- 
times be  tuffs,  although  their  density  or  compactness  is  such  as  to 
cause  them  to  resemble  many  of  those  kinds  of  trap  which  are  found 
in  ordinary  dikes.  The  chocolate-coloured  mud,  which  was  poured 
for  weeks  out  of  the  crater  of  Graham's  Island,  in  the  Mediterranean, 
in  1831,  must,  when  unmixed  with  other  materials,  have  constituted 
a  stone  heavier  than  granite.  Each  cubic  inch  of  the  impalpable 
powder  which  has  fallen  for  days  through  the  atmosphere,  during 
some  modern  eruptions,  has  been  found  to  weigh,  without  being 
compressed,  as  much  as  ordinary  trap  rocks,  and  to  be  often  identical 
with  these  in  mineral  composition. 

Palagonite-tuff.—The  nature  of  volcanic  tuffs  must  vary  according 
to  the  mineral  composition  of  the  ashes  and  cinders  thrown  out  of 
each  vent,  or  from  the  same  vent,  at  different  times.  In  descrip- 
tions of  Iceland,  we  read  of  Palagonite-tuffs  as  very  common.  The 
name  Palagonite  was  first  given  by  Professor  Bunsen  to  a  mineral 
occurring  in  the  volcanic  formations  of  Palagonia,  in  Sicily.  It  is 
rather  a  mineral  substance  than  a  mineral,  as  it  is  always  amorphous, 
and  has  never  been  found  crystallized.  Its  composition  is  variable, 
but  it  may  be  defined  as  a  hydrosilicate  of  alumina,  containing  oxide 
of  iron,  lime,  magnesia,  and  some  alkali.  It  is  of  a  brown  or  black- 
ish-brown colour,  and  its  specific  density,  2 '43.  It  enters  largely 
into  the  composition  of  volcanic  tuffs  and  breccias,  and  is  considered 
by  Bunsen  as  an  altered  rock,  resulting  from  the  action  of  steam  on 
volcanic  tuffs. 

*  Geol.  Trans.  2nd  series,  vol.  ii.  p.  211. 


OH;  XXVIII.]  AGGLOMERATE  —  LATERITE.  475 

Agglomerate.  —  In  the  neighbourhood  of  volcanic  vents,  we  fre- 
quently observe  accumulations  of  angular  fragments  of  rock,  formed 
during  eruptions  by  the  explosive  action  of  steam,  which  shatters  the 
subjacent  stony  formations,  and  hurls  them  up  into  the  air.  They 
then  fall  in  showers  around  the  cone  or  crater,  or  may  be  spread  for 
some  distance  over  the  surrounding  country.  The  fragments  consist 
usually  of  different  varieties  of  scoriaceous  and  compact  lavas  ;  but 
other  kinds  of  rock,  such  as  granite  or  even  fossiliferous  limestones, 
may  be  intermixed  ;  in  short,  any  substance  through  which  the  ex- 
pansive gases  have  forced  their  way.  The  dispersion  of  such  ma- 
terials may  be  aided  by  the  wind,  as  it  varies  in  direction  or  intensity, 
and  by  the  slope  of  the  cone  down  which  they  roll,  or  by  floods  of 
rain,  which  often  accompany  eruptions.  But  if  the  power  of  run- 
ning water,  or  of  the  waves  and  currents  of  the  sea,  be  sufficient  to 
carry  the  fragments  to  a  distance,  it  can  scarcely  fail  (unless  where 
ice  intervenes)  to  wear  off  their  angles,  and  the  formation  then 
becomes  a  conglomerate.  If  occasionally  globular  pieces  of  scoriae 
abound  in  an  agglomerate,  they  do  not  owe  their  rounded  form  to 
attrition. 

The  size  of  the  angular  stones  in  some  agglomerates  is  enormous  ; 
for  they  may  be  two  or  three  yards  in  diameter.  The  mass  is  often 
50  or  100  feet  thick,  without  showing  any  marks  of  stratification. 
The  term  volcanic  breccia  may  be  restricted  to  those  tuffs  which 
are  made  up  of  small  angular  pieces  of  rock. 

The  slaggy  crust  of  a  stream  of  lava  will  often,  while  yet  in 
motion,  split  up  into  angular  pieces,  some  of  which,  after  the  current 
has  ceased  to  flow,  may  be  seen  to  stick  up  five  or  six  feet  above  the 
general  surface.  Such  broken-up  crusts  resemble  closely  in  structure 
the  agglomerates  above  described,  although  the  composition  of  the 
materials  will  usually  be  more  homogeneous. 

Laterite  is  a  red,  jaspery,  or  brick-like  rock  composed  of  silicate  of 
alumina  and  oxide  of  iron.  The  red  layers,  called  "ochre-beds," 
dividing  the  lavas  of  the  Giant's  Causeway,  are  laterites.  These  were 
found  by  Delesse  to  be  trap  impregnated  with  the  red  oxide  of  iron, 
and  in  part  reduced  to  kaolin.  When  still  more  decomposed  they 
were  found  to  be  clay  coloured  by  red  ochre.  As  two  of  the  lavas 
of  the  Giant's  Causeway  are  parted  by  a  bed  of  lignite,  it  is  not  im- 
probable that  the  layers  of  laterite  seen  in  the  Antrim  cliffs  resulted 
from  atmospheric  decomposition.  In  Madeira  and  the  Canary  Is- 
lands streams  of  lava  of  subaerial  origin  are  often  divided  by  red 
bands  of  laterite,  probably  ancient  soils  formed  by  the  decomposition 
of  the  surfaces  of  lava-currents,  many  of  these  soils  having  been 
coloured  red  in  the  atmosphere  by  oxide  of  iron,  others  burnt  into 
a  red  brick  by  the  overflowing  of  heated  lavas.  These  red  bands 
are  sometimes  prismatic,  the  small  prisms  being  at  right  angles  to 
the  sheets  of  lava.  Red  clay  or  red  marl,  formed  as  above  stated  by 
the  disintegration  of  lava,  scorige,  or  tuff,  has  often  accumulated  to 
a  great  thickness  in  the  valleys  of  Madeira,  being  washed  into  them 
by  alluvial  action ;  and  some  of  the  thick  beds  of  laterite  in  India 


476  MINERAL   COMPOSITION  [Cn.  XXVIII. 

may  have  had  a  similar  origin.  In  India,  however,  especially  in 
the  Deccan,  the  term  "  laterite  "  seems  to  have  been  used  too  vaguely. 
It  would  be  tedious  to  enumerate  all  the  varieties  of  trap  and 
lava  which  have  been  regarded  by  different  observers  as  sufficiently 
abundant  to  deserve  distinct  names,  especially  as  each  investigator  is 
too  apt  to  exaggerate  the  importance  of  local  varieties  which  happen 
to  prevail  in  districts  best  known  to  him.  It  will  be  useful,  however, 
to  subjoin  here,  in  the  form  of  a  glossary,  an  alphabetical  list  of  the 
names  and  synonyms  most  commonly  in  use,  with  brief  explanations, 
to  which  I  have  added  a  table  of  the  analysis  of  the  simple  minerals 
most  abundant  in  the  volcanic  and  hypogene  rocks. 

Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of 
the  more  abundant  Volcanic  Rocks. 

AGGLOMERATE.  A  coarse  breccia:  composed  of  fragments  of  rock,  cast  out  of 
volcanic  vents,  for  the  most  part  angular  and  without  any  admixture  of 
water-worn  stones.  "  Volcanic  conglomerates  "  may  be  applied  to  mixtures 
in  which  water-worn  stones  occur. 

APHANITE.     See  Cornean. 

AMPHIBOLITE,  or  HORNBLENDE  ROCK,  which  see. 

AMYGDALOID.    A  particular  form  of  volcanic  rock ;  see  p.  472. 

AUGITE  ROCK.  A  rock  of  the  basaltic  family,  composed  of  felspar  and  augite. 
See  p.  470. 

AUGITIC-PORPHYRT.  Crystals  of  Labrador-felspar  and  of  augite,  in  a  green  or 
dark  grey  base.  (Rose,  Ann.  des  Mines,  torn.  8.  p.  22.  1835.) 

BASALT.    An  intimate  mixture  of  felspar  and  augite  with  magnetic  iron,  olivine, 

&c.     See  p.  470. 
BASANITE.     Name  given  by  Alex.  Brongniart  to  a  rock,  having  a  base  of  basalt, 

with  more  or  less  distinct  crystals  of  augite  disseminated  through  it. 

CLAYSTONE  and  CLAYSTONE-PORPHYRY.  An  earthy  and  compact  stone,  usually  of 
a  purplish  colour,  like  an  indurated  clay ;  passes  into  hornstone  ;  generally 
contains  scattered  crystals  of  felspar  and  sometimes  of  quartz. 

CLINKSTONE.  Syn.  Phonolite,  fissile  Petrosilex,  see  p.  471.;  a  greyish-blue  rock, 
having  a  tendency  to  divide  into  slabs  ;  hard,  with  clean  fracture,  ringing 
under  the  hammer ;  principally  composed  of  felspar,  and,  according  to 
Gmelin,  of  felspar  and  mesotype.  (Leonhard,  Mineralreich,  p.  102.) 

COMPACT  FELSPAR,  which  has  also  been  called  Petrosilex ;  the  rock  so  called 
includes  the  hornstone  of  some  mineralogists,  is  allied  to  clinkstone,  but  is 
harder,  more  compact,  and  translucent.  It  is  a  varying  rock,  of  which  the 
chemical  composition  is  not  well  defined.  (MacCullocKs  Classification  of 
Rocks,  p.  481.) 

CORNEAN  or  APHANITE.  A  compact  homogeneous  rock  without  a  trace  of 
crystallization,  breaking  with  a  smooth  surface  like  some  compact  basalts; 
consists  of  hornblende,  quartz,  and  felspar  in  intimate  combination.  It 
derives  its  name  from  the  Latin  word  cornu,  horn,  in  allusion  to  its 
toughness  and  compact  texture. 

DIALLAGE  ROCK.  Syn.  Euphotide,  Gabbro,  and  some  Ophiolites.  Compounded 
of  felspar  and  diallage. 

DIORITE.  A  kind  of  Greenstone,  which  see.  Components,  felspar  and  hornblende 
in  grains.  According  to  Rose,  Ann.  des  Mines,  torn.  8.  p.  4.,  diorite  consists 
of  albite  and  hornblende,  but  Delesse  has  shown  that  the  felspar  may  be 


Cif.  XXVIII.]  OF   VOLCANIC   ROCKS.  477 

Oligoclase  or  Labradorite.  (Ann.  des  Mines,  1849,  torn.  16.  p.  323.)  Its 
dark  colour  is  due  to  disseminated  plates  of  hornblende.  See  above 
p.  471. 

DOLERITE.  According  to  Rose  (ibid.  p.  32.),  its  composition  is  black  augite  and 
Labrador-felspar;  according  to  Leonhard  (Mineralreich,  &c.,  p.  77.), 
augite,  Labrador-felspar,  and  magnetic  iron.  See  above,  p.  470. 

DOMITE.    An  earthy  trachyte,  found  in  the  Puy  de  Dome,  in  Auvergne. 

EUPHOTIDE.  A  mixture  of  grains  of  Labrador-felspar  and  diallage.  (Rose,  ibid. 
p.  19.)  According  to  some,  this  rock  is  defined  to  be  a  mixture  of  augite 
or  hornblende  and  Saussurite,  a  mineral  allied  to  jade.  (Allans  Mine- 
ralogy, p.  158.)  Haidinger  first  observed  that  in  this  rock  hornblende 
surrounds  the  crystals  of  diallage. 

FELSPAR-PORPHYRY.  Syn.  Hornstone-porphyry ;  a  base  of  felspar,  with  crystals 
of  felspar,  and  crystals  and  grains  of  quartz.  See  also  Hornstone. 

GABBRO,  see  Diallage  rock. 

GREENSTONE.     Syn.  A  mixture  of  felspar  and  hornblende.     See  above,  p.  471. 

GREYSTONE.  (Graustein  of  Werner.)  Lead-grey  and  greenish  rock  composed  of 
felspar  and  augite,  the  felspar  being  more  than  seventy-five  per  cent.  (Scrope, 
Journ.  of  Sci.  No.  42.  p.  221.)  Greystone  lavas  are  intermediate  in  com- 
position between  basaltic  and  trachytic  lavas. 

HORNBLENDE  ROCK,  or  AMPHIBOLITE.  This  rock,  as  defined  by  Leonhard,  is 
composed  entirely  of  hornblende ;  but  such  a  rock  appears  to  be  exceptional, 
and  confined  to  mineral  veins.  Any  rocks  in  which  hornblende  plays  a 
conspicuous  part,  constituting  the  "  roches  amphiboliques "  of  French 
writers,  may  be  called  hornblende  rock.  They  always  contain  more  or  less 
felspar  in  their  composition,  and  pass  into  basalt  or  greenstone,  or  aphanite. 
See  p.  470. 

HORNSTONE-PORPHYRY.  A  kind  of  felspar  porphyry  (Leonhard,  loc.  cit.~),  with  a 
base  of  hornstone,  a  mineral  approaching  near  to  flint,  .differing  from 
compact  felspar  in  being  infusible. 

HYPERSTHENE  ROCK,  a  mixture  of  grains  of  Labrador-felspar  and  hypersthene 
(Rose,  Ann.  des  Mines,  torn.  8.  p.  13.),  having  the  structure  of  syenite  or 
granite  ;  abundant  among  the  traps  of  Skye.  It  is  extremely  tough,  gray- 
ish, and  greenish  black.  Some  geologists  consider  it  a  greenstone,  in  which 
hypersthene  replaces  hornblende ;  and  this  opinion,  says  Delesse,  is  borne 
out  by  the  fact  that  hornblende  usually  occurs  in  hypersthene  rock,  often 
enveloping  the  crystals  of  hypersthene.  The  latter  have  a  pearly  or  metallic- 
pearly  lustre. 

LATERITE.  A  red,  jaspery,  brick-like  rock,  composed  of  silicate  of  alumina  and 
oxide  of  iron,  or  sometimes  consisting  of  clay  coloured  with  red  ochre. 
See  above,  p.  475. 

MELAPHYRE.  A  variety  of  black  porphyry  composed  of  Labrador-felspar  and  a 
small  quantity  of  augite.  Its  black  colour  was  formerly  attributed  to  dis- 
seminated microscopic  crystals  of  augite,  but  M.  Delesse  has  shown  that 
the  paste  is  discoloured  by  hydrochloric  acid,  whereas  this  acid  does  not 
attack  the  crystals  of  augite,  which  are  seen  to  be  isolated,  and  few  in 
number.  (Ann.  des  Mines,  4th  ser.  torn.  xii.  p.  228.)  From  jteAcw,  melas, 
black. 

OBSIDIAN.    Vitreous  lava  like  melted  glass,  nearly  allied  to  pitchstone. 
OPHIOLITE.     A  name  given  by  Al.  Brongniart  to  serpentine. 
OPHITE.    A  name  given  by  Palassou  to  certain  trap  rocks  of  the  Pyrenees,  very 
variable  in  composition,  usually  composed  of  Labrador-felspar  and  horn- 


478  MINERAL   COMPOSITION  [Cn.  XXVIII. 

blende,  and  sometimes  augite,  occasionally  of  a  green  colour,  and  passing 
into  serpentine. 

PALAGONITE  TUFF.  An  altered  volcanic  tuff  containing  the  substance  termed 
palagonite.  See  p.  474. 

PEARLSTONE.  A  volcanic  rock,  having  the  lustre  of  mother  of  pearl ;  usually 
having  a  nodular  structure  ;  intimately  related  to  obsidian,  but  less  glassy. 

PEPERINO.     A  form  of  volcanic  tuff,  composed  of  basaltic  scoriae.     See  p.  474. 

PETROSILEX.     See  Clinkstone  and  Compact  Felspar. 

PHONOLITE.     Syn.  of  Clinkstone,  which  see. 

PITCHSTONE,  or  KETiNiTE  of  the  French.  Vitreous  lava,  less  glassy  than  obsidian  ; 
a  blackish  green  rock  resembling  glass,  having  a  resinous  lustre  and  ap- 
pearance of  pitch  ;  composition  usually  of  glassy  felspar  (orthoclase)  with  a 
little  mica,  quartz,  and  hornblende ;  in  Arran  it  forms  a  dike  thirty  feet 
wide,  cutting  through  sandstone. 

PUMICE.     A  light,  spongy,  fibrous  form  of  trachyte.     See  p.  473. 

PYROXENIC-PORPHYRY,  same  as  augitic- porphyry,  pyroxene  being  Hatty's  name 
for  augite. 

SCORIJE.  Syn.  volcanic  cinders  ;  reddish  brown  or  black  porous  form  of  lava. 
See  p.  473. 

SERPENTINE.  A  greenish  rock  in  which  there  is  much  magnesia.  Its  composition 
always  approaches  very  near  to  the  mineral  called  "  noble  serpentine  "  (see 
Table  of  Analyses,  p.  479.),  which  forms  veins  in  this  rock.  The  minerals 
most  commonly  found  in  Serpentine  are  diallage,  garnet,  chlorite,  oxydu- 
lous  iron,  and  chromate  of  iron.  The  diallage  and  garnet  occurring  in  ser- 
pentine are  richer  in  magnesia  than  when  they  are  crystallized  in  other 
rocks.  (Delesse,  Ann.  des  Mines,  1851,  torn,  xviii.  p.  309.)  Occurs  some- 
times, though  rarely,  in  dikes,  altering  the  contiguous  strata ;  is  indifferently 
a  member  of  the  trappean  or  hypogene  series.  Its  absence  from  recent  vol- 
canic products  seems  to  imply  that  it  belongs  properly  to  the  metamorphic 
class;  and,  even  when  it  is  found  in  dikes  cutting  through  aqueous  forma- 
tions, it  may  be  an  altered  basalt,  which  abounded  greatly  in  olivine. 

TEPHRINE,  synonymous  with  lava.  Name  proposed  by  Alex.  Brongniart. 
TOADSTONE.  A  local  name  in  Derbyshire  for  a  kind  of  wacke,  which  see. 
TRACHYTE.  Chiefly  composed  of  glassy  felspar,  with  crystals  of  glassy  felspar. 

See  p.  470. 

TRAP  TUFF.     See  p.  474. 
TRASS.    A  kind  of  tuff  or  mud  poured  out  by  lake-craters  during  eruptions  ; 

common  in  the  Eifel,  in  Germany. 
TUFF.     Syn.  Trap-tuff,  volcanic  tuff.     See  p.  474. 

VITREOUS  LAVA.     See  Pitchstone  and  Obsidian. 
VOLCANIC  TUFF.     See  p.  474. 

WACKE.     A  soft  and  earthy  variety  of  trap,  having  an  argillaceous  aspect.     It 

resembles  indurated  clay,  and  when  scratched,  exhibits  a  shining  streak. 
WHINSTONE.     A  Scotch  provincial  term  for  greenstone  and  other  hard  trap  rocks. 


CHfXXVIII.] 


OF    VOLCANIC   ROCKS. 


479 


ANALYSIS  OF  MINERALS  MOST   ABUNDANT   IN   THE  VOLCANIC  AND 
HYPOGENE  ROCKS. 


Silica. 

Alu- 

Mag- 
nesia. 

Lime. 

Potash. 

Soda. 

Iron 

Oxide. 

Man- 
ganese. 

Remainder. 

Actinolite  (Bergman)  - 
Augite,  black,  of  volcanic  rocks 
(Klaproth). 

64- 

48'OG 

"5-00 

22- 
875 

3- 
10-80 

i-oo 

43-05  C. 
0-27  W. 
12-20  W. 
11-55  W. 
8-%  W. 

f.    0-85  W. 
I   0-30  Ch. 
U-22  W. 

0-5  W. 

1-5  F. 

1-50  loss. 

1-     W. 

9-83  W. 
12-30  W. 

C    1-63  T. 
i    2-00  F. 
f    1-58F. 
I   0-90  loss. 
f   0-22  F. 
I   1-51  loss. 
J3-59  L. 
3-28  F. 
0-11  P. 
4-  18  loss. 
4-12 

12-45  W. 
13-70  W. 
10-70  W. 
5-22  W. 
5-      W. 
3-83  W. 

(   0-12  P. 
J   7-66  B. 
}    2-09  loss. 
(    1-49  F. 
f  0-22  Ph. 
|    3-56  B. 
<i    0-41  L. 
2-70  F. 
{_  377  loss. 
4-02  B. 

24-00 
56-33 

-     - 

-     - 

Chiastolite  (Landgrabe) 
Chlorite  (Kobell)         ... 

68-50 
31-14 
31  07 
25-37 

49-30 
5G-81 

37- 

66-75 
G4-91 
68-84 
71-50 

58-91 

5o-7o 
53-20 

63-25 
62-87 

35-75 
43- 

42- 

45-69 
47-88 

54-25 
53-7o 
53-42 

54-64 
46-80 
42-5 
50- 
40-00 

41-22 
37-54 

49-06 
46-23 

30-11 
17-14 
15-47 

28-79 

5-50 
2-07 

21- 
17-5 
19-16 
20-53 
15-50 

24-59 

26-5 
27-31 

23-92 
22-91 

27-25 
16- 
12- 
12-18 
8-23 

2'25 
24-6  > 

1-13 

34-40 
19-14 
17-09 

17-61 

29-68 

3-85 

19-99 
28-79 

9-43 

8-46 

24- 
0-75 
traces 

traces 
0-S9 

1-25 
1-03 

traces 
1-89 

36- 
16- 
30- 
7-32 
1G-15 

24-5 
8-53 

2~2- 
7- 
19-03  S. 

21-31  S. 
5-03  P. 

1*1 

0'53 
traces 

0-51 
0-62 

1-5 

0-25 

0-25 
0-22 
traces 

a  trace 

2- 

15-70 

ji-oe 
o-io 

1-40 

traces 
0-43 

traces 

0-46 

15-43 

2-20 

-     - 

-     - 

of"s7.~~Gotthardt  (Var- 
rentrapp). 

Diallage  of  euphotide  (Delesse)  - 

rol  (Kohler). 
Epidote  (Vauquelin)    - 
Felspar,  common  (Rose)     - 
.   ,  (Delesse) 

"O6o 
0-50 
0-40 

I'Ol 
0-32 
traces 

1-25 
0-78 
a  trace 
1-73 

4-01 

11- 

8-02 

3-23 
3-61 

12- 
11-07 

3-16 
2-53 

"3-40 
2-31 
1-39 

2-49 
9-12 
5-94 

7-59 

.  4- 
3-52 

6-88 
8-16 

L  Albite  (Rose) 

the  Vosges  (Delesse). 
Andesine,  of  syenite  from 
the  Vosges  (Deiesse). 

tique  (Dfilesse). 
Oligodase,  of  protogine 
from  Mont  Blanc  (Delesse). 

(Scheerer). 
Garnet  (  Klaproth)        ... 
(Phillips)   - 
Hornblende  (Klaproth) 
(Honsdorff) 

2-25 
18-79 
18-40 

14- 

20' 
If 

13-85 
7-05 

1-5 

a  trace 
0-14 

21-35 

10- 

561 
6-05 
7-17 

4*19 

0-65 

15-09 

5-40 

M.J 

1-00 

from  Corsica  (Delesse). 
Hypersthene  (Klaproth) 
Leucite  (Klaproth)       - 
Malacolite  or  Sahlite,  green  (De- 
lesse). 
Mesotype  (Gehlen)      - 
(Berzelius)   - 
Mica  (Klaproth)  - 
—    (Vauquelin)         - 

black  (H.  Rose)    - 
green,  of  protogine  (Delesse) 

reddish,  of  crystalline  lime- 
stone (Delesse). 

rose-coloured,  of  granite  (C. 
Gmelin). 
white,  of  pegmatite  (Delesse) 

1-38 

19-70 
26-50 
11-5 
35-  • 

12-67 
13-92 
19-80 

33-61 
33-03 

14-95 

"9-" 

0'63 

4-70 
30-32 

0-41 

2-10 
47-35 
38-5 
3S-5 

40-37 
42-61 
37-38 
28-53 
22- 
31-68 
30-5 

2-58 

0-61 

4-68 

21-72 

1-61 

9-87 

"l-33 

2-58 
0-70 

.     . 

8-87 

1-45 

3-48  S. 
1172 
12- 

18-5 

1-17 
1-69 
7-39 
1-40 
3- 

(Klaproth) 

50- 
41-0 

43-07 
41-58 
40-83 
64-85 
64- 
61-75 
6175 

37-00 

41-16 
35-48 

0-25 
0-42 
0-92 

33-09 

41-83 
34-75 

0-25 

-     - 

-     - 

roth). 
Serpentine  (Hisinger)  ... 
asbestiform  (Delesse) 

0-5 

-     . 

.     . 

1-50 

-     - 

-     - 

Steatite  (Delesse)         - 

Talc,  pure  (Delesse)    - 
(Klaproth)   - 

Tourmaline  or  Schorl,  black,  of 
Granite  from  Devon  (Rammels- 
berg). 

0-50 

275 
0-65 

2-17 
0-48 

.*{ 

1-37 
1-75 

2-5 

9-33  S. 
6-19  P. 

17-44 

i  - 

97-  S. 
1-89 

Moravia  (Rammelsberg). 
Tourmaline  (Gmelin)  - 

In  the  last  column  of  the  above  Table,  the  following  signs  are  used  :  B.  Boracic  acid,  C.  Carbonic 
acid,  Ch.  Oxide  of  Chrome,  F.  Fluoric  acid,  L.  Lithine,  P.  Phosphoric  acid,  T.  Oxide  of  Titanium, 
W.  Water.  In  the  7th  column  of  numbers,  P.  means  Protoxide,  and  S.  Sesquioxide. 


480 


TRAP   DIKES. 


[Cn.  XXIX. 


CHAPTER  XXIX. 


VOLCANIC  ROCKS — continued. 


Trap  dikes  —  sometimes  project— sometimes  leave  fissures  vacant  by  decomposi- 
tion— Branches  and  veins  of  trap  —  Dikes  more  crystalline  in  the  centre — 
Strata  altered  at  or  near  the  contact  —  Obliteration  of  organic  remains  —  Con- 
version of  chalk  into  marble — Trap  interposed  between  strata — Columnar  and 
globular  structure — Relation  of  trappean  rocks  to  the  products  of  active  vol- 
canos — Form,  external  structure,  and  origin  of  volcanic  mountains — Craters 
and  Calderas  —  Sandwich  Islands — Lava  flowing  underground  —  Truncation  of 
cones — Javanese  calderas — Canary  Islands  —  Structure  and  origin  of  the  Cal- 
dera  of  Palma — Older  and  newer  volcanic  rocks  in,  unconformable  —  Aqueous 
conglomerate  in  Palma — Hypothesis  of  upheaval  considered  —  Slope  on  which 
stony  lavas  may  form — Extent  and  natiire  of  aqueous  erosion  in  Palma — Island 
of  St.  Paul  in  the  Indian  Ocean  —  Peak  of  Teneriffe,  and  ruins  of  older  cone — 
Madeira — Its  volcanic  rocks,  partly  of  marine,  and  partly  of  subaerial  origin  — 
Central  axis  of  eruptions — Varying  dip  of  solid  lavas  near  the  axis,  and  further 
from  it — Leaf-bed,  and  fossil  land-plants  —  Central  valleys  of  Madeira  not 
craters,  or  calderas. 

HAVING  in  the  last  chapter  spoken  of  the  composition  and  mineral 
characters  of  volcanic  rocks,  I  shall  next  describe  the  manner 
and  position  in  which  they  occur  in  the  earth's  crust,  and  their 
external  forms.  The  leading  varieties  both  of  the  basaltic  and 
trachytic  rocks,  as  well  as  of  greenstone  and  the  rest,  are  found 
sometimes  in  dikes  penetrating  stratified  and  unstratified  formations, 
sometimes  in  shapeless  masses  protruding  through  or  overlying 
them,  or  in  horizontal  sheets  intercalated  between  strata. 

Volcanic  or  trap  dikes. — Fissures  have  already  been  spoken  of  as 
occurring  in  all  kinds  of  rocks,  some  a  few  feet,  others  many  yardy 
in  width,  and  often  filled  up  with  earth  or  angular  pieces  of  stone, 
or  with  sand  and  pebbles.  Instead  of  such  materials,  suppose  a 

quantity  of  melted  stone  to  be 
driven  or  injected  into  an  open 
rent,  and  there  consolidated, 
we  have  then  a  tabular  mass 
resembling  a  wall,  and  called 
a  trap  dike.  It  is  not  un- 
common to  find  such  dikes 
passing  through  strata  of  soft 
materials,  such  as  tuff,  scoriae, 
or  shale,  which,  being  more 
perishable  than  the  trap,  are 
often  washed  away  by  the 

Dike  in  valley,  near  Brazen  Head,  Madeira.  gea    rivers,   Or  rain,  in  which 

(From  a  drawing  of  Capt.  Basil  Hall,  R.N.) 


Fig.  624. 


CH.  XXIX.] 


TKAP   DIKES   AND   VEINS. 


481 


Fig.  625. 


case  the  dike  stands  prominently  out  in  the  face  of  precipices,  or  on 
the  level  surface  of  a  country. 

In  the  islands  of  Arran  and  Skye,  and  in  other  parts  of  Scotland, 
where  sandstone,  conglomerate,  and  other  hard  rocks  are  traversed  by 
dikes  of  trap,  the  converse  of  the  above  phenomenon  is  seen.  The 
dike,  having  decomposed  more  rapidly  than  the  containing  rock,  has 
once  more  left  open  the  original  fissure,  often  for  a  distance  of  many 
yards  inland  from  the  sea-coast,  as 
represented  in  the  annexed  view  (fig. 
625.).  In  these  instances,  the  green- 
stone of  the  dike  is  usually  more  tough 
and  hard  than  the  sandstone ;  but  che- 
mical action,  and  chiefly  the  oxidation 
of  the  iron,  has  given  rise  to  the  more 
rapid  decay. 

There   is    yet    another    case,   by  no 
means  uncommon  in  Arran  and  other 
parts  of  Scotland,  where  the  strata  in 
contact  with  the  dike,  and  for  a  certain 
distance  from  it,  have  been  hardened,  so 
as  to  resist  the  action  of  the  weather 
Fissures  left  vacant  by  decomposed   more  than  the  dike  itself,  or  the  sur- 
loch.)  scrathaird'  skye'   <MacCuU  rounding   rocks.     When   this   happens, 
two   parallel  walls  of  indurated  strata 

are  seen  protruding   above  the  general  level  of  the  country  and 
following  the  course  of  the  dike. 

As  fissures  sometimes  send  off  branches,  or  divide  into  two  or 
more  fissures  of  equal  size,  so  also  we  find  trap  dikes  bifurcating 
and  ramifying,  and  sometimes  they  are  so  tortuous  as  to  be  called 
veins,  though  this  is  more  common  in 
granite  than  in  trap.  The  accompanying 
sketch  (fig.  626.)  by  Dr.  MacCulloch  re- 
presents part  of  a  sea-cliff  in  Argyleshire, 
where  an  overlying  mass  of  trap,  b,  sends 
out  some  veins  which  terminate  down- 
wards. Another  trap  vein,  a  «,  cuts 
through  both  the  limestone,  c,  and  the 
trap,  b. 

In  fig.  627.,  a  ground  plan  is  given  of 
a  ramifying  dike  of  greenstone,  which  I  observed  cutting  through 

Fig.  627. 


Fig.  626 


Trap  veins  in  Airdnamurchan. 


Ground  plan  of  greenstone  dike  traversing  sandstone.    Arran. 
I  I 


482  VARIOUS   FOKMS   OF  [Cfl.  XXIX. 

sandstone  on  the  beach  near  Kildonan  Castle,  in  Arran.  The 
larger  branch  varies  from  5  to  7  feet  in  width,  which  will  afford  a 
scale  of  measurement  for  the  whole. 

In  the  Hebrides  and  other  countries,  the  same  masses  of  trap 
which  occupy  the  surface  of  the  country  far  and  wide,  concealing 
the  subjacent  stratified  rocks,  are  seen  also  in  the  sea  cliffs,  pro- 
longed downwards  in  veins  or  dikes,  which  probably  unite  with 
other  masses  of  igneous  rock  at  a  greater  depth.  The  largest  of  the 
dikes  represented  in  the  annexed  diagram,  and  which  are  seen  in 
part  of  the  coast  of  Skye,  is  no  less  than  100  feet  in  width. 

Fig.  628. 


Trap  dividing  and  covering  sandstone  near  Suishnish  in  Skye.    (MacCulloch.) 

Every  variety  of  trap-rock  is  sometimes  found  in  dikes,  as  basalt, 
greenstone,  felspar-porphyry,  and  trachyte.  The  amygdaloidal 
traps  also  occur,  though  more  rarely,  and  even  tuff  and  breccia,  for 
the  materials  of  these  last  may  be  washed  down  into  open  fissures  at 
the  bottom  of  the  sea,  or  during  eruptions  on  the  land  may  be 
showered  into  them  from  the  air. 

Some  dikes  of  trap  may  be  followed  for  leagues  uninterruptedly 
in  nearly  a  straight  direction,  as  in  the  north  of  England,  showing 
that  the  fissures  which  they  fill  must  have  been  of  extraordinary 
length. 

In  many  cases  trap  at  the  edges  or  sides  of  a  dike  is  less  crys- 
talline or  more  earthy  than  in  the  centre,  in  consequence  of  the 
melted  matter  having  cooled  more  rapidly  by  coming  in  contact 
with  the  cold  sides  of  the  fissure  ;  whereas,  in  the  centre,  where  the 
matter  of  the  dike  is  kept  longer  in  a  fluid  or  soft  state,  crystals  are 
slowly  formed.  But  I  observed  the  converse  of  the  above  phe- 
nomena in  Teneriffe,  in  the  neighbourhood  of  Santa  Cruz,  where  a 
dike  is  seen  cutting  through  horizontal  beds  of  scoriae  in  the  sea- 
cliff  near  the  Barranco  de  Bufadero.  It  is  vertical  in  its  main 
direction,  slightly  flexuous,  and  about  one  foot  thick.  On  each  side 
are  walls  of  compact  basalt,  but  in  the  centre  the  rock  is  highly 
vesicular  for  a  width  of  about  4  inches.  In  this  instance,  the 
fissure  may  have  become  wider  after  the  lava  on  each  side  had 
consolidated,  and  the  additional  melted  matter  poured  into  the 
middle  space  may  have  cooled  more  rapidly  than  that  at  the  sides. 

In  the  ancient  part  of  Vesuvius,  called  Somma,  a  thin  band  of 
half-vitreous  lava  is  found  at  the  edge  of  some  dikes.  At  the 
junction  of  greenstone  dikes  with  limestone,  a  sahlband,  or  selvage, 
of  serpentine  is  occasionally  observed.  On  the  left  shore  of  the 
fiord  of  Christiania,  in  Norway,  I  examined,  in  company  with 
Professor  Keilhau,  a  remarkable  dike  of  syenitic  greenstone,  which 
is  traced  through  Silurian  strata,  until  at  length,  in  the  promontory 


CH.  XXIX.] 


TRAP   DIKES   AND   VEINS. 


483 


Fig.  629. 

Syenitic  greenstone  dike  of  Naesodden, 
Christiania. 


Green 
stone. 


of  Nassodden,  it  enters  mica- 
schist.  Fig.  629.  represents  a 
ground  plan,  where  the  dike 
appears  8  paces  in  width.  In 
the  middle  it  is  highly  crystal- 
line and  granitiform,  of  a  purplish 
colour,  and  containing  a  few 
crystals  of  mica,  and  strongly 
contrasted  with  the  whitish  mica- 
schist,  between  which  and  the 
syenitic  rock  there  is  usually  on 
each  side  a  distinct  black  band, 

b.  imbedded  fragment  of  crystalline  schist  sur-     18    inches    wide,    of    dark    STeen- 
rounded  by  a  band  of  greenstone.  .^_^  ' 

stone.      When   first   seen,   these 

bands  have  the  appearance  of  two  accompanying  dikes ;  yet  they 
are,  in  fact,  only  the  different  form  which  the  syenitic  materials 
have  assumed  where  near  to  or  in  contact  with  the  mica-schist. 
At  one  point,  a,  one  of  the  sahlbands  terminates  for  a  space ;  but 
near  this  there  is  a  large  detached  block,  ft,  having  a  gneiss-like 
structure,  consisting  of  hornblende  and  felspar,  which  is  included  in 
the  midst  of  the  dike.  Round  this  a  smaller  encircling  zone  is  seen, 
of  dark  basalt,  or  fine-grained  greenstone,  nearly  corresponding  to 
the  larger  ones  which  border  the  dike,  but  only  1  inch  wide. 

It  seems,  therefore,  evident  that  the  fragment,  ft,  has  acted  on  the 
matter  of  the  dike,  probably  by  causing  it  to  cool  more  rapidly,  in 
the  same  manner  as  the  walls  of  the  fissure  have  acted  on  a  larger 
scale.  The  facts,  also,  illustrate  the  facility  with  which  a  graniti- 
form syenite  may  pass  into  ordinary  rocks  of  the  volcanic  family. 
The  fact  above  alluded  to,  of  a  foreign  fragment,  such  as  ft, 

fig.  629.,  included  in  the  midst 
of  the  trap,  as  if  torn  off  from 
some  subjacent  rock  or  the  walls 
•of  a  fissure,  is  by  no  means  un- 
common. A  fine  example  is 
seen  in  another  dike  of  green- 
stone, 10  feet  wide,  in  the 
northern  suburbs  of  Christiania, 
in  Norway,  of  which  the  an- 
nexed figure  is  a  ground  plan. 
The  dike  passes  through  shale, 
known  by  its  fossils  to  belong  to 
the  Silurian  series.  In  the 
black  base  of  greenstone  are  angular  and  roundish  pieces  of  gneiss, 
some  white,  others  of  a  light  flesh-colour,  some  without  lamination, 
like  granite,  others  with  laminae,  which,  by  their  various  and  often 
opposite  directions,  show  that  they  have  been  scattered  at  random 
through  the  matrix.  These  imbedded  pieces  of  gneiss  measure  from 
1  to  about  8  inches  in  diameter. 

Rocks  altered  by  volcanic  dikes. — After  these  remarks  on  the  form 

II  2 


Fig.  630. 


Greenstone  dike,  with  fragments  of  gueiaa. 
Sorgenfria,  Christiania. 


484  ROCKS   ALTERED   BY    TRAP    DIKES.          [Cn.  XXIX. 

and  composition  of  dikes  themselves,  I  shall  describe  the  alterations 
which  they  sometimes  produce  in  the  rocks  in  contact  with  them. 
The  changes  are  usually  such  as  the  intense  heat  of  melted  matter 
and  the  entangled  gases  might  be  expected  to  cause. 

Plas-Newydd. — A  striking  example,  near  Plas-Newydd,  in 
Anglesea,  has  been  described  by  Professor  Henslow.*  The  dike  is 
134  feet  wide,  and  consists  of  a  rock  which  is  a  compound  of  felspar 
and  augite  (dolerite  of  some  authors).  Strata  of  shale  and  argilla- 
ceous limestone,  through  which  it  cuts  perpendicularly,  are  altered 
to  a  distance  of  30,  or  even,  in  some  places,  to  35  feet  from  the  edge, 
of  the  dike.  The  shale,  as  it  approaches  the  trap,  becomes  gradually 
more  compact,  and  is  most  indurated  where  nearest  the  junction. 
Here  it  loses  part  of  its  schistose  structure,  but  the  separation  into 
parallel  layers  is  still  discernible.  In  several  places  the  shale  is  con- 
verted into  hard  porcellanous  jasper.  In  the  most  hardened  part  of 
the  mass  the  fossil  shells,  principally  Product^  are  nearly  obliter- 
ated ;  yet  even  here  their  impressions  may  frequently  be  traced. 
The  argillaceous  limestone  undergoes  analogous  mutations,  losing  its 
earthy  texture  as  it  approaches  the  dike,  and  becoming  granular  and 
crystalline.  But  the  most  extraordinary  phenomenon  is  the  appear- 
ance in  the  shale  of  numerous  crystals  of  analcime  and  garnet,  which 
are  distinctly  confined  to  those  portions  of  the  rock  affected  by  the 
dike.f  Some  garnets  contain  as  much  as  20  per  cent,  of  lime,  which 
they  may  have  derived  from  the  decomposition  of  the  fossil  shells  or 
Producti.  The  same  mineral  has  been  observed,  under  very  ana- 
logous circumstances,  in  High  Teesdale,  by  Professor  Sedgwick, 
where  it  also  occurs  in  shale  and  limestone,  altered  by  basalt.^ 

Antrim. — In  several  parts  of  the  county  of  Antrim,  in  the  north 
of  Ireland,  chalk  with  flints  is  traversed  by  basaltic  dikes.  The 
chalk  is  there  converted  into  granular  marble  near  the  basalt,  the 
change  sometimes  extending  8  or  10  feet  from  the  wall  of  the  dike, 
being  greatest  near  the  point  of  contact,  and  thence  gradually  de- 
creasing till  it  becomes  evanescent.  "  The  extreme  effect,"  says  Dr. 
Berger,  "  presents  a  dark  brown  crystalline  limestone,  the  crystals 
running  in  flakes  as  large  as  those  of  coarse  primitive  (metamorphic) 
limestone ;  the  next  state  is  saccharine,  then  fine  grained  and  arena- 
ceous ;  a  compact  variety,  having  a  porcellanous  aspect  and  a  bluish- 
grey  colour,  succeeds  :  this,  towards  the  outer  edge,  becomes  yellow- 
ish-white, and  insensibly  graduates  into  the  unaltered  chalk.  The 
flints  in  the  altered  chalk  usually  assume  a  grey  yellowish  colour."  § 
All  traces  of  organic  remains  are  effaced  in  that  part  of  the  lime- 
stone which  is  most  crystalline. 

The  annexed  drawing  (fig.  631.)  represents  three  basaltic  dikes 
traversing  the  chalk,  all  within  the  distance  of  90  feet.  The  chalk 
contiguous  to  the  two  outer  dikes  is  converted  into  a  finely  granular 
marble,  m  m,  as  are  the  whole  of  the  masses  between  the  outer  dikes 


Cambridge    Transactions,    vol.  i.        J  Ibid.  vol.  ii.  p.  175._ 
12.  §  Dr.  Berge: 

f  Ibid.  vol.  i.  p.  410.  vol.  iii.  p.  172. 


p.  402.  §  I>r.  Berger,  Geol.  Trans.  1st  series, 

rol.  iii.  p. 


Ci.  XXIX.]          ROCKS   ALTERED   BY   TRAP   DIKES.  485 

Fig.  631. 


7^|f|i  ~  '  ••,  ^ /\^::^.:.'-v>'-? 
flifltt 


Ill  Illlmlllllillllll 


Dike  35  ft.          Dike  Dike  20  ft. 

1  foot. 

Basaltic  dikes  in  chalk  in  island  of  Rathlin,  Antrim. 
Ground  plan,  as  seen  on  the  beach.    (Conybeare  and  Buckland.*) 

and  the  central  one.  The  entire  contrast  in  the  composition  and 
colour  of  the  intrusive  and  invaded  rocks,  in  these  cases,  renders  the 
phenomena  peculiarly  clear  and  interesting. 

Another  of  the  dikes  of  the  north-east  of  Ireland  has  converted  a 
mass  of  red  sandstone  into  hornstone.  By  another,  the  shale  of  the 
coal-measures  has  been  indurated,  assuming  the  character  of  flinty 
slate;  and  in  another  place  the  slate-clay  of  the  lias  has  been 
changed  into  flinty  slate,  which  still  retains  numerous  impressions  of 
ammonites,  f 

It  might  have  been  anticipated  that  beds  of  coal  would,  from  their 
combustible  nature,  be  affected  in  an  extraordinary  degree  by  the 
contact  of  melted  rock.  Accordingly,  one  of  the  greenstone  dikes  of 
Antrim,  on  passing  through  a  bed  of  coal,  reduces  it  to  a  cinder  for 
the  space  of  9  feet  on  each  side. 

At  Cockfield  Fell,  in  the  north  of  England,  a  similar  change  is 
observed.  Specimens  taken  at  the  distance  of  about  30  yards  from 
the  trap  are  not  distinguishable  from  ordinary  pit-coal ;  those  nearer 
the  dike  are  like  cinders,  and  have  all  the  character  of  coke ;  while 
those  close  to  it  are  converted  into  a  substance  resembling  soot.J 

As  examples  might  be  multiplied  without  end,  I  shall  merely 
select  one  or  two  others,  and  then  conclude.  The  rock  of  Stirling 
Castle  is  a  calcareous  sandstone,  fractured  and  forcibly  displaced  by 
a  mass  of  greenstone  which  has  evidently  invaded  the  strata  in  a 
melted  state.  The  sandstone  has  been  indurated,  and  has  assumed  a 
texture  approaching  to  hornstone  near  the  junction.  In  Arthur's 
Seat  and  Salisbury  Craig,  near  Edinburgh,  a  sandstone  which  comes 
in  contact  with  greenstone  is  converted  into  a  jaspideous  rock. 

The  secondary  sandstones  in  Skye  are  converted  ftito  solid  quartz 
in  several  places,  where  they  come  in  contact  with  veins  or  masses 
of  trap ;  and  a  bed  of  quartz,  says  Dr.  MacCulloch,  found  near  a 
mass  of  trap,  among  the  coal  strata  of  Fife,  was  in  all  probability  a 
stratum  of  ordinary  sandstone,  having  been  subsequently  indurated 
and  turned  into  quartzite  by  the  action  of  heat.§ 

But  although  strata  in  the  neighbourhood  of  dikes  are  thus  altered 

*  Geol.  Trans.  1st  series,  vol.  iii.  J  Sedgwick,  Camb.  Trans.  voL  ii. 
p.  210.  and  plate  10.  p.  37. 

t  Ibid.  p.  213. ;  and  Playfair,  Blust.          §  Syst.  of  Geol.  vol.  i.  p.  206. 
of  Hutt.  Theory,  s.  253. 

II  3 


486  INTRUSION   OF    TRAP    BETWEEN    STRATA.       [Cn.  XXIX. 

in  a  variety  of  cases,  shale  being  turned  into  flinty  slate  or  jasper, 
limestone  into  crystalline  marble,  sandstone  into  quartz,  coal  into 
coke,  and  the  fossil  remains  of  all  such  strata  wholly  and  in  part 
obliterated,  it  is  by  no  means  uncommon  to  meet  with  the  same  rocks, 
even  in  the  same  districts,  absolutely  unchanged  in  the  proximity  of 
volcanic  dikes. 

This  great  inequality  in  the  effects  of  the  igneous  rocks  may  often 
arise  from  an  original  difference  in  their  temperature,  and  in  that  of 
the  entangled  gases,  such  as  is  ascertained  to  prevail  in  different 
lavas,  or  in  the  same  lava  near  its  source  and  at  a  distance  from  it. 
The  power  also  of  the  invaded  rocks  to  conduct  heat  may  vary, 
according  to  their  composition,  structure,  and  the  fractures  which 
they  may  have  experienced,  and  perhaps,  also,  according  to  the  quan- 
tity of  water  (so  capable  of  being  heated)  which  they  contain.  It 
must  happen  in  some  cases  that  the  component  materials  are  mixed 
in  such  proportions  as  prepare  them  readily  to  enter  into  chemical 
union,  and  form  new  minerals ;  while  in  other  cases  the  mass  may 
be  more  homogeneous,  or  the  proportions  less  adapted  for  such 
union. 

We  must  also  take  into  consideration,  that  one  fissure  may  be  sim- 
ply filled  with  lava,  which  may  begin  to  cool  from  the  first ;  whereas 
in  other  cases  the  fissure  may  give  passage  to  a  current  of  melted 
matter,  which  may  ascend  for  days  or  months,  feeding  streams  which 
are  overflowing  the  country  above,  or  are  ejected  in  the  shape  of 
scoriae  from  some  crater.  If  the  walls  of  a  rent,  moreover,  are 
heated  by  hot  vapour  before  the  lava  rises,  as  we  know  may  happen 
on  the  flanks  of  a  volcano,  the  additional  caloric  supplied  by  the  dike 
and  its  gases  will  act  more  powerfully. 

Intrusion  of  trap  between  strata.  —  In  proof  of  the  mechanical 
force  which  the  fluid  trap  has  sometimes  exerted  on  the  rocks  into 
which  it  has  intruded  itself,  I  may  refer  to  the  Whin- Sill,  where  a 
mass  of  basalt,  from  60  to  80  feet  in  height,  represented  by  «, 
fig.  632.,  is  in  part  wedged  in  between  the  rocks  of  limestone,  b,  and 

Fig.  632. 

Basalt. 


Trap  interposed  between  displaced  beds  of  limestone  and  shale,  at  White 
Force,  High  Teesdale,  Durham.    (Sedgwick.*) 

shale,  c,  which  have  been  separated  from  the  great  mass  of  limestone 
and  shale,  d,  with  which  they  were  united. 

*  Camb.  Trans,  vol.  ii.  p.  1 80. 


CH.  XXIX.]         STRUCTURE   OF   VOLCANIC   ROCKS. 


487 


The  shale  in  this  place  is  indurated ;  and  the  limestone,  which  at 
a  distance  from  the  trap  is  blue,  and  contains  fossil  corals,  is  here 
converted  into  granular  marble  without  fossils. 

Masses  of  trap  are  not  unfrequently  met  with  intercalated  between 
strata,  and  maintaining  their  parallelism  to  the  planes  of  stratifica- 
tion throughout  large  areas.  They  must  in  some  places  have  forced 
their  way  laterally  between  the  divisions  of  the  strata,  a  direction  in 
which  there  would  be  the  least  resistance  to  an  advancing  fluid,  if 
no  vertical  rents  communicated  with  the  surface,  and  a  powerful 
hydrostatic  pressure  were  caused  by  gases  propelling  the  lava 
upwards. 

Columnar  and  globular  structure.  —  One  of  the  characteristic 
forms  of  volcanic  rocks,  especially  of  basalt,  is  the  columnar,  where 
large  masses  are  divided  into  regular  prisms,  sometimes  easily  sepa- 
rable, but  in  other  cases  adhering  firmly  together.  The  columns 
vary  in  the  number  of  angles,  from  three  to  twelve  ;  but  they  have 
most  commonly  from  five  to  seven  sides.  They  are  often  divided 
transversely,  at  nearly  equal  distances,  like  the  joints  in  a  vertebral 
column,  as  in  the  Giants'  Causeway,  in  Ireland.  They  vary  exceed- 
ingly in  respect  to  length  and  diameter.  Dr.  MacCulloch  mentions 
some  in  Skye  which  are  about  400  feet  long  ;  others,  in  Morven,  not 
exceeding  an  inch.  In  regard  to  diameter,  those  of  Ailsa  measure  9 
feet,  and  those  of  Morven  an  inch  or  less.*  They  are  usually  straight, 
but  sometimes  curved ;  and  examples  of  both  these  occur  in  the 
island  of  Staffa.  In  a  horizontal  bed  or  sheet  of  trap  the  columns 
are  vertical ;  in  a  vertical  dike  they  are  horizontal.  Among  other 
examples  of  the  last-mentioned  phenomenon  is  the  mass  of  basalt, 
called  the  Chimney,  in  St.  Helena  (see  fig.  633),  a  pile  of  hexagonal 


Fig.  633. 


Fig.  634. 


Small  portion  of  the  dyke 
in  Fig.  633. 


Volcanic  dyke  composed  of  hori- 
zontal prisms.     St.  Helena. 


prisms,  64  feet  high,  evidently  the  remainder  of  a  narrow  dike,  the 
walls  of  rock  which  the  dike  originally  traversed  having  been  re- 

*  MacCul.  Syst  of  Geol.  vol.  ii.  p.  137. 
ii  4 


488 


STRUCTURE  OF  VOLCANIC  ROCKS.    [Cn.  XXIX. 


moved  down  to  the  level  of  the  sea.     In  fig.  634.,  a  small  portion  of 
this  dike  is  represented  on  a  less  reduced  scale.* 

It  being  assumed  that  columnar  trap  has  consolidated  from  a  fluid 
state,  the  prisms  are  said  to  be  always  at  right  angles  to  the  cooling 
surfaces.  If  these  surfaces,  therefore,  instead  of  being  either  per- 
pendicular or  horizontal,  are  curved,  the  columns  ought  to  be  inclined 
at  every  angle  to  the  horizon  ;  and  there  is  a  beautiful  exemplifica- 
tion of  this  phenomenon  in  one  of  the  valleys  of  the  Vivarais,  a 
mountainous  district  in  the  South  of  France,  where,  in  the  midst  of 
a  region  of  gneiss,  a  geologist  encounters  unexpectedly  several 
volcanic  cones  of  loose  sand  and  scoriae.  From  the  crater  of  one  of 
these  cones,  called  La  Coupe  d'Ayzac,  a  stream  of  lava  descends  and 
occupies  the  bottom  of  a  narrow  valley,  except  at  those  points  where 
the  river  Volant,  or  the  torrents  which  join  it,  have  cut  away  portions 
of  the  solid  lava.  The  accompanying  sketch  (fig.  635.)  represents  the 


Fig.  635. 


Lava  of  La  Coupe  d'Ayzac,  near  Antraigue,  in  the  province  of  Ardeche. 

remnant  of  the  lava  at  one  of  the  points  where  a  lateral  torrent  joins 
the  main  valley  of  the  Volant.  It  is  clear  that  the  lava  once  filled 
the  whole  valley  up  to  the  dotted  line  d  a ;  but  the  river  has  gra- 
dually swept  away  all  below  that  line,  while  the  tributary  torrent  has 
laid  open  a  transverse  section ;  by  which  we  perceive,  in  the  first 
place,  that  the  lava  is  composed,  as  usual  in  this  country,  of  three 
parts :  the  uppermost,  at  a,  being  scoriaceous ;  the  second,  b,  pre- 
senting irregular  prisms;  and  the  third,  c,  with  regular  columns, 
which  are  vertical  on  the  banks  of  the  Volant,  where  they  rest  on  a 
horizontal  base  of  gneiss,  but  which  are  inclined  at  an  angle  of  45°  at 
<7,  and  are  horizontal  at  f,  their  position  having  been  every  where 
determined,  according  to  the  law  before  mentioned,  by  the  concave 
form  of  the  original  valley. 

In  the  annexed  figure  (636.)  a  view  is  given  of  some  of  the  in- 
clined and  curved  columns  which  present  themselves  on  the  sides 
of  the  valleys  in  the  hilly  region  north  of  Vicenza,  in  Italy,  and 
at  the  foot  of  the  higher  Alps.f  Unlike  those  of  the  Vivarais,  last 
mentioned,  the  basalt  of  this  country  was  evidently  submarine,  and 
the  present  valleys  have  since  been  hollowed  out  by  denudation. 


*  Seale's  Geognosy  of   St.   Helena, 
plate  9. 


f  Fortis.   Mem.  sur  1'Hist.  Nat.  de 
1'Italie,  torn,  i.  p.  233.  plate  7. 


CH.  XXIX.]         STRUCTURE   OF   VOLCANIC   ROCKS. 


489 


Fig.  636. 


The  columnar  structure  is  by  no  means 
peculiar  to  the  trap  rocks  in  which 
augite  abounds ;  it  is  also  observed  in 
clinkstone,  trachyte,  and  other  felspathic 
rocks  of  the  igneous  class,  although  in 
these  it  is  rarely  exhibited  in  such  re- 
gular polygonal  forms. 

It  has  been  already  stated  that  basaltic 
columns  are  often  divided  by  cross  joints. 
Sometimes  each  segment,  instead  of  an 
angular,  assumes  a  spheroidal  form,  so 
that  a  pillar  is  made  up  of  a  pile  of 
balls,  usually  flattened,  as  in  the  Cheese- 
grotto  at  Bertrich-Baden,  in  the  Eifel, 
near  the  Moselle  (fig.  637.).  The  basalt  there  is  part  of  a  small 
stream  of  lava,  from  30  to  40  feet  thick,  which  has  proceeded  from 


Columnar  basalt  in  the  Vicentin. 
(Fortis.) 


Basaltic  pillars  of  the  Kasegrotte,  Bertrich-Baden,  half  way  between  Treves  and  Coblentz. 
Height  of  grotto,  from  7  to  8  feet. 

one  of  several  volcanic  craters,  still  extant,  on  the  neighbouring 
heights.  The  position  of  the  lava  bordering  the  river  in  this  valley 
might  be  represented  by  a  section  like  that  already  given  at  fig.  635. 
if  we  merely  supposed  inclined  strata  of  slate  and  the  argillaceous 
sandstone  called  greywacke  to  be  substituted  for  gneiss. 

In  some  masses  of  decomposing  greenstone,  basalt,  and  other  trap 
rocks,  the  globular  structure  is  so  conspicuous  that  the  rock  has  the 
appearance  of  a  heap  of  large  cannon  balls.  According  to  the  theory 
of  M.  Delesse,  the  centre  of  each  spheroid  has  been  a  centre  of  crys- 
tallization, around  which  the  different  minerals  of  the  rock  arranged 
themselves  symmetrically  during  the  process  of  cooling.  But  it  was 
also,  he  says,  a  centre  of  contraction,  produced  by  the  same  cooling. 
The  globular  form,  therefore,  of  such  spheroids  is  the  combined 
result  of  crystallization  and  contraction.* 


*  Delesse,  ur  les  Roches  Globuleuses,  Mem.  de  la  Soc.  Geol.  de  France,  2  ser. 
torn.  iv. 


490 


RELATION    OF    TRAP, 


[CH.  XXIX. 


Fig.  638. 


A  striking  example  of  this  structure  occurs  in  a  resinous  trachyte 
or  pitchstone-porphyry  in  one  of  the  Ponza  islands,  which  rise  from 
the  Mediterranean,  off  the  coast  of  Terracina  and  Gaeta.  The 
globes  vary  from  a  few  inches  to  three 
feet  in  diameter,  and  are  of  an  ellipsoidal 
form  (see  fig.  638.).  The  whole  rock  is 
in  a  state  of  decomposition,  "  and  when 
the  balls,"  says  Mr.  Scrope,  "  have  been 
exposed  a  short  time  to  the  weather,  they 
scale  off  at  a  touch  into  numerous  con- 
centric coats,  like  those  of  a  bulbous  root, 
inclosing  a  compact  nucleus.  The  laminae 
of  this  nucleus  have  not  been  so  much 
loosened  by  decomposition ;  but  the  appli- 
cation of  a  ruder  blow  will  produce  a  still 
further  exfoliation."  * 

A  fissile  texture  is  occasionally  assumed 
by  clinkstone  and  other  trap  rocks,  so  that 
they  have  been  used  for  roofing  houses. 
Sometimes  the  prismatic  and  slaty  struc- 
ture is  found  in  the  same  mass.  The 
causes  which  give  rise  to  such  arrange- 
ments are  very  obscure,  but  are  supposed 
to  be  connected  with  changes  of  temperature  during  the  cooling  of 
the  mass,  as  will  be  pointed  out  in  the  sequel.  (See  Chaps.  XXXV. 
and  XXXYI.) 


Globiform  pitchstone.     Chiaja  di 
Luna,  Isle  of  Ponza.   (Scrope.) 


Relation  of  Trappean  Rocks  to  the  products  of  active  Volcanos. 

When  we  reflect  on  the  changes  above  described  in  the  strata  near 
their  contact  with  trap  dikes,  and  consider  how  complete  is  the 
analogy  or  often  identity  in  composition  and  structure  of  the  rocks 
called  trappean  and  the  lavas  of  active  volcanos,  it  seems  difficult  at 
first  to  understand  how  so  much  doubt  could  have  prevailed  for  half 
a  century  as  to  whether  trap  was  of  igneous  or  aqueous  origin.  To 
a  certain  extent,  however,  there  was  a  real  distinction  between  the 
trappean  formations  and  those  to  which  the  term  volcanic  was  almost 
exclusively  confined.  A  large  portion  of  the  trappean  rocks  first 
studied  in  the  north  of  Germany,  and  in  Norway,  France,  Scotland, 
and  other  countries,  were  such  as  had  been  formed  entirely  under 
water,  or  had  been  injected  into  fissures  and  intruded  between  strata, 
and  which  had  never  flowed  out  in  the  air,  or  over  the  bottom  of  a 
shallow  sea.  When  these  products,  therefore,  of  submarine  or  sub- 
terranean igneous  action  were  contrasted  with  loose  cones  of  scoriae, 
tuff,  and  lava,  or  with  narrow  streams  of  lava  in  great  part  scoria- 
ceous  and  porous,  such  as  were  observed  to  have  proceeded  from 
Vesuvius  and  Etna,  the  resemblance  seemed  remote  and  equivocal. 


*  Scrope,  Geol.  Trans.  2d  series,  vol.  ii.  p.  205. 


CH.  XXIX.]  LAVA,   AND   SCORL2E.  491 

It  was,  in  truth,  like  comparing  the  roots  of  a  tree  with  its  leaves 
and  branches,  which,  although  they  belong  to  the  same  plant,  differ 
in  form,  texture,  colour,  mode  of  growth,  and  position.  The  external 
cone,  with  its  loose  ashes  and  porous  lava,  may  be  likened  to  the 
light  foliage  and  branches,  and  the  rocks  concealed  far  below,  to  the 
roots.  But  it  is  not  enough  to  say  of  the  volcano, 

"  quantum  vertice  in  auras 
JEtherias,  tantum  radice  in  Tartara  tendit," 

for  its  roots  do  literally  reach  downwards  to  Tartarus,  or  to  the 
regions  of  subterranean  fire;  and  what  is  concealed  far  below  is 
probably  always  more  important  in  volume  and  extent  than  what  is 
visible  above  ground. 

We  have  already  stated  how  frequently  dense  masses  of  strata 
have  been  removed  by  denudation  from  wide  areas  (see  Chap.  YI.) ; 

and  this  fact  prepares  us  to  expect  a 
similar  destruction  of  whatever  may 
once  have  formed  the  uppermost  part 
of  ancient  submarine  or  subaerial  vol- 
canos,  more  especially  as  those  super- 
ficial parts  are  always  of  the  lightest 
and  most  perishable  materials.  The 
abrupt  manner  in  which  dikes  of  trap 
usually  terminate  at  the  surface  (see 
>and  fig-  639.),  and  the  water-worn  pebbles 
of  trap  in  the  alluvium  which  covers 

the  dike,  prove  incontestably  that  whatever  was  uppermost  in  these 
formations  has  been  swept  away.  It  is  easy,  therefore,  to  conceive 
that  what  is  gone  in  regions  of  trap  may  have  corresponded  to  what 
is  now  visible  in  active  volcanos. 

It  will  be  seen  in  the  following  chapters,  that  in  the  earth's  crust 
there  are  volcanic  tuffs  of  all  ages,  containing  marine  shells,  which 
bear  witness  to  eruptions  at  many  successive  geological  periods. 
These  tuffs,  and  the  associated  trappean  rocks,  must  not  be  compared 
to  lava  and  scoriae  which  had  cooled  in  the  open  air.  Their  counter- 
parts must  be  sought  in  the  products  of  modern  submarine  volcanic 
eruptions.  If  it  be  objected  that  we  have  no  opportunity  of  studying 
these  last,  it  may  be  answered,  that  subterranean  movements  have 
caused,  almost  everywhere  in  regions  of  active  volcanos,  great 
changes  in  the  relative  level  of  land  and  sea,  in  times  comparatively 
modern,  so  as  to  expose  to  view  the  effects  of  volcanic  operations  at 
the  bottom  of  the  sea. 

Thus,  for  example,  the  examination  of  the  igneous  rocks  of  Sicily, 
especially  those  of  the  Val  di  Noto,  has  proved  that  all  the  more 
ordinary  varieties  of  European  trap  have  been  there  produced  under 
the  waters  of  the  sea,  at  a  modern  period ;  that  is  to  say,  since  the 
Mediterranean  has  been  inhabited  by  a  great  proportion  of  the 
existing  species  of  testacea. 


492  RELATION   OF    TRAP,  [Cn.  XXIX. 

These  igneous  rocks  of  the  Val  di  Noto,  and  the  more  ancient 
trappean  rocks  of  Scotland  and  other  countries,  differ  from  sub- 
aerial  volcanic  formations  in  being  more  compact  and  heavy,  and 
in  forming  sometimes  extensive  sheets  of  matter  intercalated  be- 
tween marine  strata,  and  sometimes  stratified  conglomerates,  of 
which  the  rounded  pebbles  are  all  trap.  They  differ  also  in  the 
absence  of  regular  cones  and  craters,  and  in  the  want  of  conformity 
of  the  lava  to  the  lowest  levels  of  existing  valleys. 

It  is  highly  probable,  however,  that  insular  cones  did  exist  in 
some  parts  of  the  Val  di  Noto :  and  that  they  were  removed  by  the 
waves,  in  the  same  manner  as  the  cone  of  Graham  Island,  in  the 
Mediterranean,  was  swept  away  in  1831,  and  that  of  Nyoe,  off 
Iceland,  in  1783.*  All  that  would  remain  in  such  cases,  after  the 
bed  of  the  sea  has  been  upheaved  and  laid  dry,  would  be  dikes  and 
shapeless  masses  of  igneous  rock,  cutting  through  sheets  of  lava 
which  may  have  spread  over  the  level  bottom  of  the  sea,  and  strata 
of  tuff,  formed  of  materials  first  scattered  far  and  wide  by  the  winds 
and  waves,  and  then  deposited.  Conglomerates  also,  with  pebbles 
of  trap,  to  which  the  action  of  the  waves  must  give  rise  during  the 
denudation  of  such  volcanic  islands,  will  emerge  from  the  deep 
whenever  the  bottom  of  the  sea  becomes  land.  The  proportion  of 
volcanic  matter  which  is  originally  submarine  must  always  be  very 
great,  as  those  volcanic  vents  which  are  not  entirely  beneath  the 
sea  are  almost  all  of  them  in  islands,  or,  if  on  continents,  near  the 
shore. 

As  to  the  absence  of  porosity  in  the  trappean  formations,  the 
appearances  are  in  a  great  degree  deceptive,  for  all  amygdaloids  are, 
as  already  explained,  porous  rocks,  into  the  cells  of  which  mineral 
matter  such  as  silex,  carbonate  of  lime,  and  other  ingredients,  have 
been  subsequently  introduced  (see  p.  473.) ;  sometimes,  perhaps,  by 
secretion  during  the  cooling  and  consolidation  of  lavas. 

In  the  Little  Cumbray,  one  of  the  Western  Islands,  near  Arran, 
the  amygdaloid  sometimes  contains  elongated  cavities  filled  with 
brown  spar;  and  when  the  nodules  have  been  washed  out,  the 
interior  of  the  cavities  is  glazed  with  the  vitreous  varnish  so  cha- 
racteristic of  the  pores  of  slaggy  lavas.  Even  in  some  parts  of  this 
rock  which  are  excluded  from  air  and  water,  the  cells  are  empty, 
and  seem  to  have  always  remained  in  this  state,  and  are  therefore 
undistinguishable  from  some  modern  lavas.f 

Dr.  MacCulloch,  after  examining  with  great  attention  these,  and 
the  other  igneous  rocks  of  Scotland,  observes,  "that  it  is  a  mere 
dispute  about  terms,  to  refuse  to  the  ancient  eruptions  of  trap  the 
name  of  submarine  volcanoes ;  for  they  are  such  in  every  essential 
point,  although  they  no  longer  eject  fire  and  smoke."  J  The  same 
author  also  considers  it  not  improbable  that  some  of  the  volcanic 

*  See  Princ.  of  Geol.,  Index,  "Gra-          f  MacCulloch,  West.  Islands,  vol.  ii. 
ham  Island,"  "Nyoe,"  "Conglomerates,      p.  487. 
volcanic,"  &c.  J  Syst.  of  GeoL  vol.  ii.  p.  114. 


-On.  XXIX.]  LAVA,   AND   SCORIAE.  493 

rocks  of  the  same  country  may  have  been  poured  out  in  the  open 
air.* 

Although  the  principal  component  minerals  of  subaerial  lavas  are 
the  same  as  those  of  intrusive  trap,  and  both  the  columnar  and 
globular  structure  are  common  to  both,  there  are,  nevertheless,  some 
volcanic  rocks  which  never  occur  in  currents  of  lava,  such  as 
greenstone,  the  more  crystalline  porphyries,  and  those  traps  in 
which  quartz  and  mica  appear  as  constituent  parts.  In  short,  the 
intrusive  trap  rocks,  forming  the  intermediate  step  between  lava 
and  the  plutonic  rocks,  depart  in  their  characters  from  lava  in 
proportion  as  they  approximate  to  granite. 

These  views  respecting  the  relations  of  the  volcanic  and  trap 
rocks  will  be  better  understood  when  the  reader  has  studied,  in  the 
33rd  chapter,  what  is  said  of  the  plutonic  formations 

EXTERNAL  FORM,   STRUCTURE,  AND  ORIGIN  OF   VOLCANIC  MOUNTAINS. 

The  origin  of  volcanic  cones  with  crater-shaped  summits  has  been 
alluded  to  in  the  last  chapter  (p.  466.),  and  more  fully  explained  in 
the  "Principles  of  Geology"  (chaps,  xxiv.  to  xxvii.),  where  Ve- 
suvius, Etna,  Santorin,  and  Barren  Island  are  described.  The  more 
ancient  portions  of  those  mountains  or  islands,  formed  long  before 
the  times  of  history,  exhibit  the  same  external  features  and  internal 
structure  which  belong  to  most  of  the  extinct  volcanos  of  still 
higher  antiquity;  and  these  last  have  evidently  been  due  to  a 
complicated  series  of  operations,  varied  in  kind  according  to  cir- 
cumstances ;  as,  for  example,  whether  the  accumulation  took  place 
above  or  below  the  level  of  the  sea,  whether  the  lava  issued  from 
one  or  several  contiguous  vents,  and,  lastly,  whether  the  rocks  re- 
duced to  fusion  in  the  subterranean  regions  happen  to  have  contained 
more  or  less  silica,  potash,  soda,  lime,  iron,  and  other  ingredients. 

We  are  best  acquainted  with  the  effects  of  eruptions  above  water, 
or  those  called  subaerial  or  supramarine ;  yet  the  products  even  of 
these  are  arranged  in  so  many  ways  that  their  interpretation  has 
given  rise  to  a  variety  of  contradictory  opinions,  some  of  which  will 
have  to  be  considered  in  this  chapter. 

Craters  and  Calderas,  Sandwich  Islands.  —  We  learn  from 
Mr.  Dana's  valuable  work  on  the  geology  of  the  United  States' 
Exploring  Expedition,  published  in  1849,  that  two  of  the  principal 
volcanos  of  the  Sandwich  Islands,  Mounts  Loa  and  Kea  in  Owyhee, 
are  huge  flattened  volcanic  cones,  about  1400  feet  high  (see  fig.  640.), 
each  equalling  two  and  a  half  Etnas  in  their  dimensions. 

From  the  summits  of  these  lofty  though  featureless  hills,  and  from 
vents  not  far  below  their  summits,  successive  streams  of  lava,  often 
2  .miles  or  more  in  width,  and  sometimes  26  miles  long,  have  flowed. 
They  have  been  poured  out  one  after  the  other,  some  of  them  in 
recent  times,  in  every  direction  from  the  apex  of  the  cone,  down 

*  Syst.  of  Geol.,  vol.  ii.  p.  114. 


494      EXTERNAL  FORM,  STRUCTURE,  AND  ORIGIN       [€H.  XXIX. 

a  Fig.  640. 


Mount  Loa,  in  the  Sandwich  Islands.    (Dana.) 

a.  Crater  at  the  summit.  b.  The  lateral  crater  of  Kilauea. 

The  dotted  lines  indicate  a  supposed  column  of  solid  rock  caused  by  the  lava  consolidating 
after  eruptions. 

slopes  varying  on  an  average  from  4  degrees  to  8  degrees ;  but  in 
some  places  considerably  steeper.  Sometimes  deep  rents  are  formed 
on  the  sides  of  these  conical  mountains,  which  are  afterwards  filled 
from  above  by  streams  of  lava  passing  over  them,  the  liquid  matter 
in  such  cases  consolidating  in  the  fissures  and  forming  dikes. 

The  lateral  crater  of  Kilauea,  b,  fig.  640.,  is  3970  feet  above  the 
level  of  the  sea,  or  about  the  same  height  as  Vesuvius.  It  is  an 
immense  chasm,  1000  feet  deep,  and  its  outer  circuit  no  less  than 
from  two  to  three  miles  in  diameter.  Lava  is  usually  seen  to  boil 
up  at  the  bottom  in  a  lake,  the  level  of  which  alters  continually,  for 
the  liquid  rises  and  falls  several  hundred  feet  according  to  the 
active  or  quiescent  state  of  the  volcano.  But  instead  of  overflowing 
the  rim  of  the  crater,  as  commonly  happens  in  other  vents,  the 
column  of  melted  rock,  when  its  pressure  becomes  excessive,  forces 
a  passage  through  some  subterranean  galleries  or  rents  leading 
towards  the  sea.  Mr.  Coan,  an  American  missionary,  has  described 
an  eruption  which  took  place  in  June  1840,  when  the  lava  which 
had  risen  high  in  the  great  chasm  began  to  escape  from  it.  I!s 
direction  was  first  recognised  by  the  emission  of  a  vivid  light  from 
the  bottom  of  an  ancient  wooded  crater,  called  Arare,  400  feet  deep 
and  6  miles  to  the  eastward  of  Kilauea.  The  connection  of  this 
light  with  the  discharge  or  tapping  of  the  great  reservoir  was 
proved  by  a  change  in  the  level  of  the  lava  in  Kilauea,  which  sank 
gradually  for  three  weeks,  or  until  the  eruption  ceased,  when  the 
lake  stood  400  feet  lower  than  at  the  commencement  of  the  outbreak. 
The  passage,  therefore,  of  the  fluid  matter  from  Kilauea  to  Arare 
was  underground,  and  it  is  supposed  by  Mr.  Coan  to  have  been  at 
its  first  outflow  1000  feet  deep  below  the  surface.  The  next 
indication  of  the  subterranean  progress  of  the  same  lava  was 
observed  a  mile  or  two  from  Arare,  where  the  fiery  flood  broke  out 
and  spread  itself  superficially  over  50  acres  of  land,  and  then  again 
found  its  way  underground  for  several  miles  farther  towards  the 
sea,  to  reappear  at  the  bottom  of  a  second  ancient  and  wooded 
crater,  which  it  partly  filled  up.  The  course  of  the  fluid  then 
became  again  invisible  for  several  miles,  until  it  broke  out  for  the 
last  time  at  a  point  ascertained  by  Captain  Wilkes  to  be  1244  feet 
above  the  sea,  and  27  miles  distant  from  Kilauea.  From  thence  it 
poured  along  for  12  miles  in  the  open  air,  and  then  leapt  over 
a  cliif  50  feet  high,  and  ran  for  three  weeks  into  the  sea.  Its 
termination  was  at  a  place  about  40  miles  distant  from  Kilauea. 
The  crust  of  the  earth  overlying  the  subterranean  course  of  the  lava 
was  often  traversed  by  innumerable  fissures,  which  emitted  steam, 
and  in  some  places  the  incumbent  rocks  were  uplifted  20  or  30  feet. 


CH.  XXIX.]  OF   VOLCANIC    MOUNTAINS.  495 

Thus  in  the  same  volcano  examples  are  afforded  of  the  overflowing 
of  lava  from  the  summit  of  a  cone  2\  miles  high,  and  of  the  under- 
flowing  of  melted  matter.  Whether  this  last  has  formed  sheets 
intercalated  between  the  stratified  products  of  previous  eruptions, 
or  whether  it  has  penetrated  through  oblique  or  vertical  fissures, 
cannot  be  determined.  In  one  instance,  however,  for  a  certain 
space,  it  is  said  to  have  spread  laterally,  uplifting  the  incumbent 
soil. 

The  annexed  section  of  the  crater  of  Kilauea,  as  given  by 
Mr.  Dana,  follows  the  line  of  its  shorter  diameter,  a,  £,  which  is 

Fig.  641. 


Section  of  the  crater  of  Kilauea  in  the  Sandwich  Islands.    (Dana.) 
a,  b.  External  boundaries  of  the  chasm  in  the  line  of  its  shortest  diameter. 
c,  e,  f,  d.   Black  ledge.  g,  h.  Lake  of  lava. 

about  7500  feet  long.  The  boundary  cliffs,  «,  c  and  b,  d,  are  for  the 
most  part  quite  vertical  and  650  feet  high.  They  are  composed  of 
compact  rock  in  layers,  not  divided  by  scoriae,  some  a  few  inches, 
others  30  feet  in  thickness,  and  nearly  horizontal.  Below  this,  we 
come  to  what  is  called  the  "  black  ledge,"  c,  e  and  /,  d,  composed  of 
similar  stratified  materials.  This  ledge  is  342  feet  in  height  above 
the  lake  of  lava,  #,  A,  which  it  encircles.  The  chasm,  «,  b,  and  its 
walls  have  probably  been  due  to  a  former  sinking  down  of  the 
incumbent  rocks,  undermined  for  a  space  by  the  fusion  of  their 
foundations.  The  lower  ledge,  c,  e  and  f,  d,  may  consist  in  part  of 
the  mass  which  sank  vertically,  but  part  of  it  at  least  must  be  made 
up  of  layers  of  lava,  which  have  been  seen  to  pour  one  after  the 
other  over  the  "  black  ledge."  If  at  any  future  period  the  heated 
fluid,  ascending  from  the  volcanic  focus  to  the  bottom  of  the  great 
chasm,  should  augment  in  volume,  and,  before  it  can  obtain  relief, 
should  spread  itself  subterraneously,  it  may  melt  still  farther  the 
subjacent  masses,  and,  causing  a  failure  of  support,  may  enlarge  still 
more  the  limits  of  the  amphitheatre  of  Kilauea.  There  are  distinct 
signs  of  subsidences,  from  100  to  200  feet  perpendicular,  which 
have  occurred  in  the  neighbourhood  of  Kilauea  at  various  points, 
and  they  are  each  bounded  by  vertical  walls.  If  all  of  them  were 
united,  they  would  constitute  a  sunken  area  equal  to  eight  square 
miles,  or  twice  the  extent  of  Kilauea  itself.  Similar  accidents  are 
also  likely  to  occur  near  the  summit  of  a  dome  like  Mount  Loa,  for 
the  hydrostatic  pressure  of  the  lava,  after  it  has  risen  to  the  edge  or 
lip  of  the  highest  crater,  a,  fig.  640.,  must  be  great  and  must  create 
a  tendency  to  lateral  fissuring,  in  which  case  lava  will  be  injected 
into  every  opening,  and  may  begin  to  undermine.  If,  then,  some  of 
the  melted  matter  be  drawn  off  by  escaping  at  a  lower  level,  where 


496      EXTERNAL  FORM,  STRUCTURE,  AND  ORIGIN       [Cn.  XXIX. 

the  pressure  would  be  still  greater,  the  whole  top  of  the  mountain, 
or  a  large  part  of  it,  might  fall  in. 

Instances  of  such  truncations,  however  caused,  have  occurred  in 
Java  and  in  the  Andes  within  the  times  of  history,  and  to  such  events 
we  may  perhaps  refer  a  very  common  feature  in  the  configuration  of 
volcanic  mountains,  —  namely,  that  the  present  active  cone  of  erup- 
tion is  surrounded  by  the  ruins  of  a  larger  and  older  cone,  usually 
presenting  a  crescent-shaped  precipice  towards  the  newer  cone.  In 
volcanos  long  since  extinct,  the  erosive  power  of  running  water,  or, 
in  certain  cases,  of  the  sea,  may  have  greatly  modified  the  shape  of 
the  "  atrium,"  or  space  between  the  older  and  newer  cone,  and  the 
cavity  may  thereby  be  prolonged  downwards,  and  end  in  a  ravine. 
In  such  cases  it  may  be  impossible  to  determine  how  much  of  the 
missing  rocks  has  been  removed  by  explosion  at  the  time  when 
the  original  crater  was  active,  or  how  much  by  subsequent  engulph- 
ment  and  denudation. 

Java.  —  One  of  the  latest  contributions  to  our  knowledge  of  vol- 
canos will  be  found  in  Dr.  Junghuhn's  work  on  Java,  where  forty- 
six  conical  eminences  of  volcanic  origin,  varying  in  elevation  from 
4000  to  nearly  12,000  feet  above  the  sea,  constitute  the  highest 
peaks  of  a  mountain  range,  running  through  the  island  from  east  to 
west.  All  of  them,  with  one  exception,  did  this  indefatigable  traveller 
survey  and  map.  In  none  of  them  could  he  discover  any  marine 
remains,  whether  adhering  to  their  flanks  or  entering  into  their  in- 
ternal structure,  although  strata  of  marine  origin  are  met  with 
nearer  the  sea  at  lower  levels.  Dr.  Junghuhn  ascribes  the  origin  of 
each  volcano  to  a  succession  of  subaerial  eruptions  from  one  or  more 
central  vents,  whence  scoriae,  pumice,  and  fragments  of  rock  were 
thrown  out,  and  whence  have  flowed  streams  of  trachytic  or  basaltic 
lava.  Such  overflowings  have  been  witnessed  in  modern  times  from 
the  highest  summits  of  several  of  the  peaks.  The  external  slope  of 
each  cone  is  generally  greatest  near  its  apex,  where  the  volcanic 
strata  have  also  the  steepest  dip,  sometimes  attaining  angles  of  20, 
30,  and  35  degrees,  but  becoming  less  and  less  inclined  as  they  recede 
from  the  summit,  until,  near  their  base,  the  dip  is  reduced  to  10  and 
often  4  or  5  degrees.*  The  interference  of  the  lavas  of  adjoining 
volcanos  sometimes  produces  elevated  platforms,  or  "saddles,"  in 
which  the  layers  of  rock  may  be  very  slightly  inclined.  At  the  top 
of  many  of  the  loftiest  mountains  the  active  cone  and  crater  are 
of  small  size,  and  surrounded  by  a  plain  of  ashes  and  sand,  this 
plain  being  encircled  in  its  turn  by  what  Dr.  Junghuhn  calls  "  the 
old  crater -wall,"  which  is  often  1000  feet  and  more  in  vertical  height. 
There  is  sometimes  a  terrace  of  intermediate  height  (as  in  the  moun- 
tain called  Tengger),  comparable  to  the  "black  ledge"  of  Kilauea 
(fig.  641).  Most  of  the  spaces  thus  bounded  by  semicircular  or  more 
than  semicircular  ranges  of  cliffs  are  vastly  superior  in  dimensions  to 

*  Java,  deszelfs  gedaante,  bekleeding  huhn.  (German  translation  of  2d  edit, 
en  invendige  structuur,  door  .F.  Jung-  by  Hasskarl,  Leipzig,  1852.) 


CH,  XXIX.]  JAVANESE   C  ALDER  AS.  497 

the  area  of  any  known  crater  or  hollow  which  has  been  observed  in 
any  part  of  the  world  to  be  occupied  by  a  lake  of  liquid  lava.  As 
the  Spaniards  have  given  to  such  large  cavities  the  name  of  Caldera 
(or  cauldron),  it  may  be  useful  to  use  this  term  in  a  technical  sense, 
whatever  views  we  may  entertain  as  to  their  origin.  Many  of  them 
in  Java  are  no  less  than  four  geographical  miles  in  diameter,  and  they 
are  attributed  by  Junghuhn  to  the  truncation  by  explosion  and  sub- 
sidence of  ancient  cones  of  eruption.  Unfortunately,  although  several 
lofty  cones  have  lost  a  portion  of  their  height  within  the  memory  of 
man,  neither  the  inhabitants  of  Java  nor  their  Dutch  rulers  have 
transmitted  to  us  any  reliable  accounts  of  the  order  of  events  which 
occurred.* 

Dr.  Junghuhn  believes  that  Papandayang  lost  some  portion  of  its 
summit  in  1772  ;  but  affirms  that  most  of  the  towns  on  its  sides  said 
to  have  been  engulphed  were  in  reality  overflowed  by  lava. 

From  the  highest  parts  of  many  Javanese  calderas  rivers  flow, 
which  in  the  course  of  ages  have  cut  out  deep  valleys  in  the  moun- 
tain's side.  As  a  general  rule,  the  outer  slopes  of  each  cone  are 
furrowed  by  straight  and  narrow  ravines  from  200  to  600  feet  deep, 
radiating  in  all  directions  from  the  top,  and  increasing  in  number  as 
we  descend  to  lower  zones.  The  ridges  or  "  ribs,"  intervening  be- 
tween these  furrows,  are  very  conspicuous,  and  compared  to  the 
spokes  of  an  umbrella.  In  a  mountain  above  10,000  feet  high,  no 
farrows  or  intervening  ribs  are  met  with  in  the  upper  300  or  400 
feet.  At  the  height  of  10,000  feet  there  may  be  no  more  than  10  in 
number,  whereas  500  feet  lower  32  of  them  may  be  counted.  They 
are  all  ascribed  to  the  action  of  running  water ;  and  if  they  ever  cut 
through  the  rim  of  a  caldera,  it  is  only  because  the  cone  has  been 
truncated  so  low  down  as  to  cause  the  summit  to  intersect  a  middle 
region,  where  the  torrents  once  exerted  sufficient  power  to  cause  a 
series  of  such  indentations.  It  appears  from  such  facts,  that,  if  a  cone 
escapes  destruction  by  explosion  or  engulphment,  it  may  remain  un- 
injured in  its  upper  portion,  while  there  is  time  for  the  excavation 
of  deep  ravines  by  lateral  torrents. 

It  is  remarked  by  Dr.  Junghuhn,  as  also  by  Mr.  Dana  in  regard  to 
the  Pacific  Islands,  that  volcanic  mountains,  however  large  and 
however  much  exposed  to  heavy  falls  of  rain,  support  no  rivers  so 
long  as  they  are  in  the  process  of  growth,  or  while  the  highest 
crater  emits  from  time  to  time  showers  of  scoriae  and  floods  of  lava. 
Such  ejectamenta  and  such  currents  of  melted  rock  fill  up  each 
superficial  inequality  or  depression  where  water  might  otherwise 
collect,  and  are  moreover  so  porous  that  no  rill  of  water,  however 
small,  can  be  generated.  But  where  the  subterranean  fires  have  been 
long  since  spent,  or  are  nearly  exhausted,  and  where  the  superficial 
scoriae  and  lavas  decompose  and  become  covered  with  clayey  soils, 
the  corrosive  action  of  water  begins  to  operate  with  a  prodigious 
force,  proportionate  to  the  steepness  of  the  declivities  and  the  in- 

*  See  Principles  of  Geol.,  9th  edit.  p.  493. 
KK 


498 


CANARY   ISLANDS. 


[Cn.  XXIX. 


Fig,  642, 


Briera  Pi 


BarloventO 


coherent  nature  of  the  sand  and  ashes.  Even  the  more  solid  lavas 
are  occasionally  cavernous,  and  almost  always  alternate  with  scorice 
and  perishable  tuffs,  so  as  to  be  readily  undermined,  and  most  of 
them  are  speedily  reduced  to  fragments  of  a  transportable  size  be- 
cause they  are  divided  by  vertical  joints  or  split  into  columns. 

Canary  Islands  —  Palma.  —  I  have  enlarged  so  fully  in  the  "  Prin- 
ciples of  Geology"  on  the  different  views  entertained  by  eminent 
authorities  respecting  the  origin  of  volcanic  cones,  and  the  laws 
governing  the  flow  of  lava,  and  its  consolidation,  that,  in  order  not 
to  repeat  here  what  I  have  elsewhere  published,  I  shall  confine 
myself  in  the  remainder  of  this  chapter  to  the  description  of  facts 
observed  by  me  during  a  recent  exploration  of  Madeira  and  some  of 
the  Canary  Islands.  In  these  excursions,  made  in  the  winter  of 
1853-4,  I  was  accompanied  by  an  active  fellow-labourer,  Mr.  Har- 
tung,  of  Konigsberg.  We  visited  among  other  places  the  beautiful 
island  of  Palma,  a  spot  rendered  classical  by  the  description  given  of 
it  in  1825  by  the  late  Leopold  Von  Buch,  who  regarded  it  as  a  type 
of  what  he  called  a  "crater  of  elevation."* 

Palma  is  16  geographical  miles  west  of  Teneriffe.     Seen  from  the 

channel  which  divides  the  two 
islands,  Palma  appears  to  consist 
of  two  principal  mountain  masses, 
the  depression  between  them 
being  at  a  (map,  fig.  642.),  or  at 
the  pass  of  Tacanda,  which  is 
about  4600  feet  above  the  sea- 
level.  The  most  northern  of 
these  masses  makes,  notwith- 
standing certain  irregularities 
hereafter  to  be  mentioned,  a  con- 
siderable approach  in  general 
form  to  a  great  truncated  cone, 
having  in  the  centre  a  huge  and 
deep  cavity  called  by  the  inha- 
bitants "  La  Caldera."  This  ca- 
vity (b,  c,  d,  e,  fig.  642.)  is  from 
3  to  4  geographical  miles  in  dia- 

^^    ^    ^    ^^    Qf   ^^ 

pices  surrounding  it  vary  from  about  1500  to  2500  feet  in  vertical 
height.  From  their  base  a  steep  slope,  clothed  by  a  splendid  forest 
of  pines,  descends  for  a  thousand  and  sometimes  two  thousand  feet 
lower,  the  centre  of  the  Caldera  being  about  2000  feet  above  the  sea. 
The  northern  half  of  the  encircling  ridge  is  more  than  7000  English 
feet  above  the  sea  in  its  highest  peaks,  and  is  annually  white  with 
snow  during  the  winter  months. 

Externally  the  flanks  of  this  truncated  cone  incline  outwards  in 
every  direction,  the  slopes  being  steepest  near  the  crest,  and  lessening 


nyr:Mlles 


HuencalientcP? 


Map  of  Palma,  from  Survey  of  Capt  Vidal,  R.N. 


Erhcbung's  Crater. 


CH.  XXIX.] 


CALDERA   OF   PALMA. 


499 


as  they  approach  the  lower  country.  A  great  number  of  ravines 
commence  on  the  flanks  of  the  mountain,  a  short  distance  below  the 
summit,  shallow  at  first,  but  getting  deeper  as  they  descend,  and 
becoming  at  the  same  time  more  numerous,  as  in  the  cones  of  Java 
before  mentioned. 

So  unbroken  is  the  precipitous  boundary-wall  of  the  Caldera, 
except  at  its  south-eastern  end,  where  the  torrent  which  drains  it 
through  a  deep  gorge  (b,  b',  fig.  643.)  issues,  that  there  is  not  even  a 
footpath  by  which  one  can  descend  into  it  save  at  one  place  called 
the  Cumbrecito  (e,  map,  fig.  642.  p.  498.).  This  Cumbrecito  is  a 
narrow  col  or  watershed  at  the  height  of  about  2000  feet  above  the 
bottom  of  the  Caldera,  and  4000  above  the  sea,  and  situated  at  the 
precise  limit  of  two  geological  formations  presently  to  be  mentioned. 
This  col  also  occurs  at  the  level  where,  in  other  parts  of  the  Caldera, 
the  vertical  precipices  join  the  talus-like,  rocky  slope,  covered  with 
pines.  The  other  or  principal  entrance  by  which  the  Caldera  is 

Fig.  643. 


Map  of  the  Caldera  of  Palma  and  the  ereat  ravine,  called  '«  Barranco  de  las  Angnstias."    From 
the  Survey  of  Capt.  Vidal,  11.  N.,  1837.     Scale,  two  geographical  miles  to  an  inch. 

KK   2 


500 


ISLAND   OP    PALMA. 


[Cn.  XXIX. 


drained  is  the  great  ravine  or  barranco,  as  it  is  called  (see  b,  b',  fig. 
643.),  which  extends  from  the  south-western  extremity  of  the  Cal- 
dera  to  the  sea,  a  distance  of  4^  geographical  miles,  in  which  space 
the  water  of  the  torrent  falls  about  1500  feet. 


View  of  the  Isle  of  Palma?  and  of  the  entrance  into  the  central  cavity  or  Caldera.    From 
Von  Buch's  "  Canary  Islands." 

This  sketch  was  taken  by  Von  Buch  from  a  point  at  sea  not 
visited  by  us,  but  we  saw  enough  to  convince  us  that  several  lateral 
cones  ought  to  have  been  introduced  on  the  great  slope  to  the  left, 
besides  numerous  deep  furrows  radiating  from  near  the  summit  to  the 
sea  (see  the  map,  fig.  643.).  The  sea  does  not  enter  the  great 
Barranco,  as  might  be  inferred  from  this  sketch. 

The  annexed  section  (fig.  645.)  passes  through  the  island  from 
Santa  Cruz  de  Palma  to  Briera  Point,  or  from  south-east  to  north- 
west (see  map,  p.  498.).  It  has  been  drawn  up  on  a  true  scale 
of  heights  and  horizontal  distances  from  the  observations  of 
Mr.  Hartung  and  my  own. 

Fig.  645. 


Section  of  the  Island  of  Palma,  from  Point  Briera,  on  the  north-west,  to  Santa  Cruz  de  Palma,  on 
the  south-east.     See  map,  fig.  642.,  p.  498. 

a,  b.  The  Caldera  (height  of  a,  6000  feet).  c.  Commencement  of  steeper  dip. 

d.  Santa  Cruz  de  Palma  or  Tedote. 

e.  Lateral  cone,  3940  feet  above  the  sea  (  Vidal's  Map). 
/.  Briera  Point. 

g.  One  of  several  outliers  of  the  upper  formation  in  centre  of  Caldera. 
S.  P.  Half-buried  cone  and  crater  of  San  Pedro. 


The  lavas  are  seen  to  be  slightly  inclined  near  the  sea  at  Santa 
Cruz,  where  we  observed  them  flowing  round  the  cone  of  San  Pedro, 
which  they  have  more  than  half  buried  without  entering  the  crater. 
On  starting  from  the  same  part  of  the  sea-coast,  and  ascending  the 
deep  Barranco  de  la  Madera,  we  saw  just  below  c  the  basaltic  lavas 
dipping  at  an  angle  of  5  degrees,  there  being  no  dikes  in  that  region. 
Farther  up,  where  the  dikes  were  still  scarce,  the  dip  of  the  beds 
increases  to  10  and  15  degrees,  and  they  become  still  steeper  as  they 
approach  the  Caldera  at  £>,  where  dikes  abound. 


CH.  XXIX.]  SECTION   OF    ISLAND   OF    PALMA. 


501 


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KK  3 


502  STRUCTUEE    AND   ORIGIN    OF    THE        [Cn.  XXIX. 

The  section  (fig.  646.)  is  at  right  angles  to  the  preceding,  and  cuts 
through  the  cone  in  the  direction  of  the  great  Barranco,  or  from 
north-east  to  south-west. 

The  lowest  of  the  two  slanting  lines,  m,  i,  descending  from  the 
Caldera  to  the  sea  along  the  bottom  of  the  Barranco,  represents  the 
present  bed  of  the  torrent ;  the  upper  line,  k,  I,  the  height  at  which 
beds  of  gravel,  derated  high  above  the  present  river-channel,  are 
visible  in  detached  patches,  shown  by  dotted  spaces  at  k,  and  to  the 
south-west  of  it,  on  the  same  slope.  These,  and  the  continuous 
stratified  gravel  and  conglomerate  lower  down  at  I  and  i,  are  newer 
than  all  the  volcanic  rocks  seen  in  this  section. 

The  upper  volcanic  formation,  to  be  described  in  the  sequel,  is 
traversed  by  numerous  dikes,  which  could  not  be  expressed  on  this 
small  scale.  The  vertical  lines  in  the  lower  formation  represent  a 
few  of  the  perpendicular  dikes  which  abound  there.  Countless 
others,  inclined  and  tortuous,  are  found  penetrating  the  same  rocks. 
The  five  outliers  of  somewhat  pyramidal  shape,  at  the  bottom  of  the 
Caldera  (on  each  side  of  m\  agree  in  structure  and  composition  with 
the  upper  formation,  and  may  have  subsided  into  their  present 
position,  if  the  Caldera  was  caused  by  engulphment,  or  may  have  slid 
down  in  the  form  of  land-slips,  if  the  cavity  be  attributed  chiefly  to 
aqueous  erosion. 

In  the  description  above  given  of  the  section  (fig.  646.),  the  cliffs 
which  wall  in  the  Caldera  are  spoken  of  as  consisting  of  two  forma- 
tions. Of  these  the  uppermost  alone  gives  rise  to  vertical  precipices, 
from  the  base  of  which  the  lower  descends  in  steep  slopes,  which, 
although  they  have  the  external  aspect  of  taluses,  are  not  in  fact 
made  up  of  broken  materials,  or  of  ruins  detached  from  the  higher 
rocks,  but  consist  of  rocks  in  place.  Both  formations  are  of  volcanic 
origin,  but  they  differ  in  composition  and  structure.  In  the  upper, 
the  beds  consist  of  agglomerate,  scoriae,  lapilli,  and  lava,  chiefly 
basaltic,  the  whole  dipping  outwards,  as  if  from  the  axis  of  the 
original  cone,  at  angles  varying  from  10  to  28  degrees.  The  solid 
lavas  do  not  constitute  more  than  a  fourth  of  the  entire  mass, 
and  are  divided  into  beds  of  very  variable  thickness,  some  scoriaceous 
and  vesicular,  others  more  compact,  and  even  in  some  cases  rudely 
columnar.  All  these  more  stony  masses  are  seen  to  thin  out  and 
come  to  an  end  wherever  they  can  be  traced  horizontally  for  a 
distance  of  a  quarter  of  a  mile,  and  usually  sooner.  Coarse  breccias 
or  agglomerates  predominate  in  the  lower  part,  as  if  the  commence- 
ment of  the  second  series  of  rocks  marked  an  era  of  violent  gaseous 
explosions.  Single  beds  of  this  aggregate  of  angular  stones  and 
scoriae  attain  a  thickness  of  from  200  to  300  feet.  They  are  united 
together  by  a  paste  of  volcanic  dust  or  spongiform  scoriae. 

At  one  point  on  the  right  side  of  the  great  Barranco,  near  its 
exit  from  the  Caldera,  we  observed  in  the  boundary  precipice  a  lofty 
column  of  amorphous  and  scoriaceous  rock  in  which  the  red  or  rust- 
coloured  scoriae  are  as  twisted  and  ropy  as  any  to  be  seen  on  the 
slopes  of  Vesuvius  ;  seeming  to  imply  that  there  was  here  an  ancient 


Ci.  XXIX.]  CALDERA   OF   PALMA.  503 

vent  or  channel  of  discharge  subsequently  buried  under  the  products 
of  newer  eruptions.  Countless  dikes,  more  or  less  vertical,  consisting 
chiefly  of  basaltic  lava,  traverse  the  walls  of  the  Caldera,  some  of 
them  terminating  upwards,  but  a  great  number  reaching  the  very 
crest  of  the  ridge,  and  therefore  having  been  posterior  in  origin  to 
the  whole  precipice. 

We  could  not  discover  in  any  one  of  the  fallen  masses  of  agglo- 
merate which  strewed  the  base  of  the  cliffs  a  single  pebble  or 
waterworn  fragment.  Each  imbedded  stone  is  either  angular  or, 
if  globular,  consists  of  scoriae  more  or  less  spongy,  and  evidently  not 
owing  its  shape  to  attrition.  It  would  be  impossible  to  account  for 
the  absence  of  waterworn  pebbles  if  the  coarse  breccia  in  question 
had  been  spread  by  aqueous  agency  over  a  horizontal  area  co- 
extensive with  the  Caldera  and  the  volcanic  rocks  which  surround 
it.  The  only  cause  known  to  us  capable  of  dispersing  such  heavy 
fragments,  some  of  them  3,  4,  or  6  feet  in  diameter,  without  blunting 
:heir  edges,  is  the  power  of  steam,  unless  indeed  we  could  suppose 
•hat  ice  had  co-operated  with  water  in  motion ;  and  the  interference 
)f  ice  cannot  be  suspected  in  this  latitude  (28°  40'),  especially  as  I 
ooked  in  vain  for  signs  of  glacial  action  here  and  in  the  other 
nountainous  regions  of  the  Canary  Islands. 

The  lower  formation  of  the  Caldera  is,  as  before  stated,  equally  of 

gneous  origin.     It  differs  in  its  prevailing  colour  from  the  upper, 

exhibiting  a  tea-green  and  in  parts  a  light  yellow  tint,  instead  of 

he  usual  brown,  lead-coloured,  or  reddish  hues  of  basalt  and  its 

;ssociated   scoriae.      Beds   of   a   light   greenish   tuff  are   common, 

'ogether  with  trachytic  and  greenstone  rocks,  the  whole  so  reti- 

tulated  by  dikes,  some  vertical,  others  oblique,  others  tortuous,  that 

ve  found  it  impossible  to  determine  the  general  dip  of  the  beds, 

ilthough  at  the  head  of  the  great  gorge  or  Barranco  they  certainly 

dp  outwards,  or  to  the  south,  as  stated  by  Yon  Buch.     But  in 

:bllowing  the  section  down  the  same  ravine,  where  the  mountain 

<alled  Alejanado  (d,  figs.  pp.  498.  and  501.)  is  cut  through,  and  where 

he  rocks  of  the  lower  formation  are  very  crystalline,  we  found  what 

s  not  alluded  to  by  the  Prussian  geologist,  that  the  beds  exposed 

;o  view  in  cliffs   1500  feet  high  have  an  anticlinal  arrangement, 

jxhibiting  first  a  southerly  and   then  a  northerly  dip   at   angles 

varying  from  20  to  40  degrees  (see  section,  fig.  646.  at  k.).    Hence  we 

may  presume   that  the   older   strata  must   have   undergone  great 

movements  before   the   upper   formation   was   superimposed.      No 

organic  remains  having  been   discovered  in  the  older   series,  we 

cannot  positively  decide  whether  it  was  of  subaerial  or  submarine 

origin.     We  can  only  affirm  that  it  has  been  produced  by  successive 

eruptions,  chiefly  of  felspathic  lavas  and  tuffs.     Many  beds  which 

probably  consisted  at  first  of  soft  tuffs  have  been  much  hardened  by 

the  contact  of  dikes  and  apparently  much  altered  by  other  plutonic 

influences,  so  that  they  have  acquired  a  semicrystalline  and  almost 

metamorphic  character. 

The  existence  of  so  great  a  mass  of  volcanic  rocks  of  ancient  date 

KK  4 


504  C  ALDER  A  OF  PALM  A.          [Cn.  XXIX. 

on  the  exact  site  of  an  equally  vast  accumulation  of  comparatively 
modern  lavas  and  scoriae  is  peculiarly  worthy  of  notice  as  a  general 
phenomenon  observed  in  very  different  parts  of  the  globe.  It  proves 
that,  notwithstanding  the  fact  in  the  past  history  of  volcanos  that 
one  region  after  another  has  been  for  ages  and  has  then  ceased  to  be 
the  chief  theatre  of  igneous  action,  still  the  activity  of  subterranean 
heat  may  often  be  persistent  for  more  than  one  geological  period  in 
the  same  place,  relaxing  perhaps  its  energies  for  a  while,  but  then 
breaking  out  afresh  with  an  intensity  as  great  as  ever. 

We  have  still  to  consider  the  mode  of  origin  of  the  higher  volcanic 
mass,  or  the  upper  series  of  rocks  with  which  the  peculiar  form  of 
the  Caldera  is  more  intimately  connected.  The  principal  question 
here  arising  is  this,  whether  the  mass  was  dome-shaped  from  the  be- 
ginning, having  grown  by  the  superposition  of  one  conical  envelope 
of  lava  and  ashes  formed  over  another,  or  whether,  as  Von  Buch 
and  his  followers  imagine,  its  component  materials  were  first  spread 
out  in  horizontal  or  nearly  horizontal  deposits  and  then  upheaved  at 
once  into  a  dome-shaped  mountain  with  a  caldera  in  its  centre. 
According  to  the  first  hypothesis  the  cone  was  built  up  gradually, 
and  completed  with  all  its  beds  dipping  as  now,  and  traversed  by  all 
its  dikes,  before  the  Caldera  originated.  According  to  the  other, 
the  Caldera  was  the  result  of  the  same  movements  which  gave  a 
dome-shaped  structure  to  the  mass,  and  which  caused  the  beds  to  be 
highly  inclined ;  in  other  words,  the  cone  and  the  Caldera  were 
produced  simultaneously.  So  singularly  opposite  are  these  views 
that  the  principal  agency  introduced  by  the  one  theory  is  upheaval 
by  the  other  subsidence.  The  very  name  of  "  Elevation  Craters ' 
points  to  the  kind  of  movement  to  which  one  school  attributes  the 
origin  of  a  cone  and  caldera ;  whereas  the  chief  agencies  appealec 
to  by  the  other  school  are  gaseous  explosions,  engulphment,  anc 
aqueous  denudation. 

The  favourable  reception  of  the  doctrine  of  upheaval  has  arisen 
from  the  following  circumstances.  Streams  of  lava,  it  is  said 
which  run  down  a  declivity  of  more  than  three  degrees  are  neve: 
stony ;  and,  if  the  slope  exceed  five  or  six  degrees,  they  are  merq 
shallow  and  narrow  strings  of  vesicular  or  fragmentary  slag. 
Whenever,  therefore,  we  find  parallel  layers  of  stony  lava,  especially 
if  they  be  of  some  thickness,  high  up  in  the  walls  of  a  caldera,  we 
may  be  sure  that  they  were  solidified  originally  on  a  very  gentle 
slope ;  and  if  they  are  now  inclined  at  angles  of  10°,  20°,  or  30°, 
not  only  they,  but  all  the  interstratified  beds  of  lapilli,  scoriae,  tuff, 
and  agglomerate,  must  have  been  at  first  nearly  flat  and  must  have 
been  afterwards  lifted  up  with  the  solid  beds  into  their  present 
position.  It  is  supposed  that  such  a  derangement  of  the  strata  could 
scarcely  fail  to  give  rise  to  a  wide  opening  near  the  centre  of 
upheaval,  and  in  the  case  of  Palma,  the  Caldera  (which  Yon  Buch 
called  "  the  hollow  axis  of  the  cone  ")  may  represent  this  breach 
of  continuity. 

Among    other    objections   to   the   elevation-crater  theory   often 


CH.  XXIX.]  HYPOTHESIS   OF   UPHEAVAL.  505 

advanced  and  never  yet  answered  are  the  following :  —  First,  in 
most  calderas,  as  in  Palma,  the  rim  of  the  great  cavity  and  the 
circular  range  of  precipices  surrounding  it  remain  entire  and 
unbroken  on  three  sides,  whereas  it  is  difficult  to  conceive  that  a 
series  of  volcanic  strata  2000  or  3000  feet  thick  could  have  once 
extended  over  an  area  six  or  seven  miles  in  its  shortest  diameter 
and  then  have  been  upraised  bodily,  so  that  the  beds  should  dip  at 
steep  angles  towards  all  points  of  the  compass  from  a  centre,  and 
yet  that  no  great  fractures  should  have  been  produced.  We  should 
expect  to  see  some  open  fissures  on  every  side,  widening  as  they 
approach  the  caldera.  The  dikes,  it  is  true,  do  undoubtedly  attest 
many  dislocations  of  the  mass,  which  have  taken  place  at  successive 
and  often  distant  periods.  But  none  of  them  can  have  belonged  to 
the  supposed  period  of  terminal  and  paroxysmal  upheaval,  for,  had 
the  caldera  existed  when  they  originated,  the  melted  matter  now 
solidified  in  each  dike  must,  instead  of  filling  a  rent,  have  flowed 
down  into  the  caldera,  tending  so  far  to  obliterate  the  great  cavity. 

The  second  objection  is  the  impossibility  of  imagining  that  so  vast 
a  series  of  agglomerates,  tuffs,  stratified  lapilli,  and  highly  scoria- 
ceous  lavas  could  have  been  poured  out  within  a  limited  area  without 
soon  giving  rise  to  a  hill,  and  eventually  to  a  lofty  mountain.  Such 
heavy  angular  fragments  as  are  seen  in  the  agglomerates,  single  beds 
of  which  are  sometimes  200  or  300  feet  thick,  must  when  hurled 
into  the  air  have  fallen  down  again  near  the  vent,  and  would  be 
arranged  in  inclined  layers  dipping  outwards  from  the  central  axis 
of  eruption.  It  is  in  perfect  accordance  with  this  hypothesis  that  we 
should  behold  agglomerates,  lapilli,  and  scoriae  predominating  in  the 
walls  of  the  Caldera ;  whereas  in  the  ravines  nearer  the  sea,  where 
the  inclination  of  the  beds  has  diminished  to  10  and  even  to  5 
degrees,  the  proportion  of  stony  as  compared  to  fragmentary  ma- 
terials is  precisely  reversed.  It  is  also  natural  that  the  dikes  should 
be  most  numerous  where  the  ejectamenta  are  to  the  more  solid  beds 
in  the  proportion  of  3  to  1,  as  at  b,  fig.  645.  p.  500. ;  while  the  dikes 
are  few  in  number  where  the  stony  lavas  predominate  (as  at  c,  ibid.). 
Many  of  the  scoriaceous  beds  at  b  may  be  the  upper  extremities  of 
currents  which  became  stony  and  compact  when  they  reached  c, 
and  flowed  over  a  more  level  country;  but  this  suggestion  cannot 
be  assented  to  by  the  advocates  of  the  upheaval  theory,  for  it  assumes 
the  existence  of  a  cone  long  before  the  time  had  arrived  for  the 
catastrophe  which  according  to  their  views  gave  rise  to  a  conical 
mountain. 

If,  however,  we  reject  the  doctrine  that  the  beds  were  tilted  by  a 
movement  posterior  to  the  accumulation  of  all  the  compact  and  frag- 
mentary rocks,  how  are  we  to  account  for  the  steepness  of  the  dip  of 
some  stony  lavas  high  up  in  the  walls  of  the  Caldera  ?  These  masses 
are  occasionally  50  or  100  feet  thick,  of  lenticular  shape,  as  seen  in 
the  cliffs  from  below,  and  to  all  appearance  parallel  to  the  associated 
layers  of  scoriae  and  lapilli.  But  unfortunately  no  one  can  climb  up 
and  determine  how  far  the  supposed  parallelism  may  be  deceptive. 


506  STONY   LAVAS   FORMED   ON   SLOPES.       [Cn.  XXIX. 

The  solid  beds  extend  in  general  over  small  horizontal  spaces,  and 
some  of  them  may  possibly  be  no  other  than  intrusive  lavas,  in  the 
nature  of  dikes,  more  or  less  parallel  to  the  layers  of  ejectamenta. 
Such  lavas,  when  the  crater  was  full,  may  have  forced  their  way 
between  highly  inclined  beds  of  scoriae  and  lapilli.  We  know  that 
lava  often  breaks  out  from  the  side  or  base  of  a  cone,  instead  of 
rising  to  the  rim  of  the  crater.  Nevertheless  one  or  two  of  the  stony 
masses  alluded  to  seemed  to  me  to  resemble  lavas  which  had  flowed 
out  superficially.  They  may  have  solidified  on  a  broad  ledge  formed 
by  the  rim  of  a  crater.  Such  a  rim  might  be  of  considerable  breadth 
after  a  partial  truncation  of  the  cone.  And  some  lavas  may  now 
and  then  have  entirely  filled  up  the  atrium,  or  what  in  the  case  of 
Somma  and  Vesuvius  is  called  the  atrio  del  cavallo,  that  is  to  say, 
the  interspace  between  the  old  and  new  cone.  When  by  the  products 
of  new  eruptions  a  uniform  slope  has  been  restored,  and  the  two  cones 
have  blended  into  one  (see  e,  d,  c,  fig.,  p.  515.),  the  next  breaking  down 
of  the  side  of  the  mountain  may  display  a  mass  of  compact  rock  of 
great  thickness  in  the  walls  of  a  caldera,  resting  upon  and  covered 
by  ejectamenta.  Other  extensive  wedges  of  solid  lava  will  be 
formed  on  the  flanks  of  every  volcanic  mountain  by  the  interference 
of  lateral,  or,  as  they  are  often  termed,  parasitic  cones,  which  check 
or  stop  the  downward  flow  of  lava,  and  occasionally  offer  deep  craters 
into  which  the  melted  matter  is  poured. 

By  aid  of  one  or  all  the  processes  above  enumerated  we  may 
certainly  explain  a  few  exceptional  cases  of  intercalated  stony  beds, 
in  the  midst  of  others  of  a  loose  and  scoriaceous  nature,  the  whole 
being  highly  inclined.  But  to  account  for  a  succession  of  compact 
and  truly  parallel  lavas  having  a  steep  dip,  we  may  suppose  that  they 
flowed  originally  down  the  flanks  of  a  cone  sloping  at  angles  of  from 
4  to  10  degrees,  as  in  many  active  volcanos,  and  that  they  acquired 
subsequently  a  steeper  inclination.  It  would  be  rash  to  assume  the 
entire  absence  of  local  disturbances  during  the  growth  of  a  volcanic 
mountain.  Some  dikes  are  seen  crossing  others  of  a  different  com- 
position, marking  a  distinctness  in  the  periods  of  their  origin.  The 
volume  of  rock  filling  such  a  multitude  of  fissures  as  we  see  indicated 
by  the  dikes  in  Palma  must  be  enormous ;  so  that,  could  it  be  with- 
drawn, the  mass  of  ejectamenta  would  collapse  and  lose  both  in  height 
and  bulk.  The  injection,  therefore,  of  all  this  matter  in  a  liquid 
state  must  have  been  attended  by  the  gradual  distension  of  the  cone, 
the  increase  of  which  I  have  elsewhere  compared  both  to  the  exo- 
genous and  endogenous  growth  of  a  tree,  as  it  has  been  effected  alike 
by  external  and  internal  accessions. 

But  the  acquisition  of  a  steeper  dip  by  such  reiterated  rendings 
and  injections  of  a  cone  is  altogether  opposed  to  the  views  of 
those  who  defend  the  upheaval  hypothesis,  because  it  draws  with  it 
the  conclusion  that  the  slopes  were  always  growing  steeper  and  steeper 
in  proportion  as  the  cone  waxed  older  and  loftier.  Once  admit  this, 
and  it  follows,  that  the  upper  layers  of  solid  lava  must  have  con- 


CH.  XXIX.]  AQUEOUS   EROSION   IN   PALMA.  507 

formed  to  surfaces  already  inclined  at  angles  of  20,  or,  in  the  case  of 
the  Caldera  of  Palma,  28  degrees. 

For  this  reason  the  defenders  of  the  upheaval  hypothesis  are  con- 
sistent with  themselves  in  assigning  the  whole  movement  by  which 
the  strata,  whether  solid  or  incoherent,  have  been  tilted,  exclusively 
to  one  terminal  catastrophe.  The  whole  development  of  subter- 
ranean force  is  represented  as  the  last  incident  in  every  series  of 
volcanic  operations,  the  closing  scene  of  the  drama ;  and  the  sudden 
and  paroxysmal  nature  of  the  catastrophe  is  inferred  from  the 
absence  of  all  signs  of  successive  and  intermittent  action  so  cha- 
racteristic of  the  antecedent  volcanic  phenomena. 

I  have  alluded  to  an  opinion  entertained  by  some  able  geologists, 
that  no  lava  can  acquire  any  degree  of  solidity  if  it  flows  down  a 
declivity  of  more  than  three  degrees.  This  doctrine  I  believe  to  be 
erroneous.  The  lava  which  has  flowed  from  the  cone  of  Llarena 
near  Port  Orotava,  in  Teneriffe,  is  very  columnar  in  parts,  and  yet 
has  descended  a  slope  of  six  degrees.  Another  stream  of  recent 
aspect  near  the  town  of  El  Passo,  in  Palma,  has  a  general  inclination 
of  ten  degrees,  and  is  remarkable  for  the  depth  and  extent  of  the 
large  basin-shaped  hollows,  20, 30,  and  35  feet  deep,  seen  everywhere 
on  its  surface.  Whenever  another  lava-current  shall  flow  down  over 
this  one,  although  its  average  inclination  will  be  the  same,  it  must 
fill  up  all  these  inequalities,  and  in  doing  so  must  give  rise  to  masses 
of  compact  and  solid  rock  20  or  30  feet  thick,  resting  upon  and 
encircled  by  vesicular  lava.  Other  lavas  north-east  of  Fuencaliente 
at  the  southern  extremity  of  Palma,  so  modern  as  to  be  still  black 
and  uncovered  with  vegetation,  descend  slopes  of  no  less  than  22 
degrees,  and  yet  contain  large  masses  of  compact  stone,  formed 
chiefly  on  the  sides  of  tunnel-shaped  cavities,  15  or  20  feet  deep,  in 
which  one  layer  has  solidified  within  another  on  the  walls  of  these 
channels,  while  in  the  central  part  the  lava  seems  to  have  remained 
fluid  so  as  to  run  out  of  the  tunnel,  leaving  an  arched  cavity,  the 
roof  of  which  has  in  most  cases  fallen  in.  The  strength  of  the  en- 
veloping crust  of  scoriae  at  the  lower  end  of  a  lava-current  in  which 
one  of  these  tunnels  existed  may  have  been  sufficient  to  arrest  the 
progress  of  the  stream  for  hours  or  days,  and  during  that  time 
solidification  may  have  occurred  under  great  hydrostatic  pressure. 

Before  taking  leave  of  Palma,  we  have  yet  to  consider  another 
distinct  point,  namely,  what  amount  of  denudation  has  taken  place 
in  the  Caldera,  and  its  environs.  Assuming  that  the  great  cavity  or 
some  part  of  it  may  have  originated  in  the  truncation  of  a  cone  in 
the  manner  before  suggested,  to  what  extent  has  its  shape  been  sub- 
sequently enlarged  or  modified  by  aqueous  erosion?  It  will  be 
remembered  that  a  conglomerate  of  well-rounded  pebbles,  no  less 
than  800  feet  thick,  was  spoken  of  as  visible  in  the  great  Barranco 
(see  description  of  section,  pp.  501,  502.).  That  conspicuous  deposit, 
3  or  4  miles  in  length,  was  evidently  derived  from  the  destruction 
of  rocks  like  those  in  the  Caldera,  for  the  present  torrent  brings 


508   ,  EXTENT  AND  NATURE  OF       [Cn.  XXIX. 

down  annually  similar  stones  of  every  size,  some  very  large,  and 
rounds  them  by  attrition  in  its  channel.  By  what  changes  in  the 
configuration  of  the  island  after  the  old  volcano  and  its  Caldera  were 
formed  was  so  vast  a  thickness  of  gravel  formed,  to  be  afterwards 
cut  through  to  a  depth  of  800  feet?  The  ravine  through  which 
the  torrent  now  flows  has  been  excavated  to  that  depth  through  the 
old  conglomerate.  The  occurrence  of  two  or  three  layers  of  con- 
temporaneous lava,  intercalated  between  the  strata  of  puddingstone, 
ought  not  to  surprise  us ;  for  even  in  historical  times  eruptions  have 
been  witnessed  in  the  southern  half  of  Palma.  Such  basaltic  lavas, 
one  of  them  columnar  in  structure,  have  not  come  down  from  the 
Caldera,  but  from  cones  much  nearer  the  sea,  and  immediately  ad- 
joining the  Barranco,  like  the  cone  of  Argual  (see  map,  p.  499.)  and 
others.  These  lavas,  of  the  same  age  as  the  conglomerate,  consist 
of  three  or  four  currents  of  limited  extent,  for  in  many  parts  of  the 
river-cliffs  no  volcanic  formation  is  visible  on  either  bank.  On  the 
right  bank  of  the  Barranco,  the  conglomerate,  when  traced  west- 
ward, is  soon  found  to  come  to  an  end  as  it  abuts  against  the  lofty 
precipice  E  (fig.  647.),  which  is  a  prolongation  of  the  western  wall 
of  the  Caldera.  Its  extent  eastward  from  b',  may  be  more  consider- 
able, but  cannot  be  ascertained,  as  it  is  concealed  under  modern 
scoria?  and  lava  spread  over  the  great  platform,  F. 

Fig.  647. 
West.  East. 


A.  Ravine  or  Barranco  de  las  Angustias,  near  its  termination  in  Palma. 

b,  b',  b".  Conglomerate,  800  fe*l  thick  in  parts. 

c,  c'.  Lava  intercalated  between  the  beds  of  conglomerate. 

d,  d'.  Another  and  older  current  of  basaltic  lava,  columnar  in  parts. 

K.  Cliff  of  ancient  volcanic  rocks  of  the  Upper  Formation  (p.  504.),  a  prolongation  of  the  western 

wall  of  the  Caldera. 
F.  Platform  on  which  the  town  of  Argual  stands. 

As  we  could  find  no  organic  remains  in  the  old  gravel,  we  have  no 
positive  means  of  deciding  whether  it  be  fluviatile  or  marine.  The 
height  of  its  base  above  the  sea,  where  it  is  800  feet  thick,  may  be 
about  350  feet,  but  patches  of  it  ascend  to  elevations  of  1000  and 
1500  feet  near  the  top  of  the  Barranco,  as  shown  at  k,  &c.,  in  section, 
fig.  646.,  p.  501.  Such  a  mass  of  gravel,  therefore,  bears  testimony 
to  the  removal  of  a  prodigious  amount  of  materials  from  the  Caldera 
by  the  action  of  water.  Whether  a  river  or  the  sea  was  the  trans- 
porting agent,  it  is  obvious  that  a  large  portion  of  the  volcanic 
materials,  consisting  of  sand,  lapilli,  and  scoriae,  before  described 


€H.  XXIX.]  AQUEOUS   EROSION   IN   PALMA.  509 

(p.  502.),  as  belonging  to  the  upper  formation  in  the  Caldera,  would 
leave  behind  them  few  pebbles.  Nearly  all  of  these  perishable 
deposits  would  be  swept  down  in  the  shape  of  mud  into  the  Atlantic. 
Even  the  hard  rounded  stones,  since  they  were  once  angular  and 
are  now  ground  down  into  pebbles,  must  have  lost  more  than  half 
their  original  bulk,  and  bear  witness  to  large  quantities  of  sedi- 
mentary matter  consigned  to  the  bed  of  the  ocean.  We  saw  in  the 
Caldera  blocks  of  huge  size  thrown  down  by  cascades  from  the  upper 
precipices  during  the  melting  of  the  snows,  a  fortnight  before  our 
visit,  and  much  destruction  was  likewise  going  on  in  the  lower  set  of 
rocks  by  the  same  agency.  We  also  learnt  that  a  great  flood  rushed 
down  the  Barranco  in  the  spring  of  1854,  shortly  before  our  arrival, 
damaging  several  houses  and  farms,  and  I  have  therefore  no  doubt 
that  the  erosive  power  even  of  rain  and  river  water,  aided  by  earth- 
quakes, might  in  the  course  of  ages  empty  out  a  valley  as  large  as  the 
Caldera,  although  probably  not  of  the  same  shape.  I  am  disposed  to 
attribute  the  circular  range  of  cliffs  surrounding  the  Caldera  to  vol- 
canic action,  because  they  forcibly  reminded  me  of  the  precipices 
encircling  three  sides  of  the  Val  del  Bove,  on  Etna ;  and  because 
they  agree  so  well  with  Junghuhn's  description  of  the  "  old  crater- 
walls  "  of  active  volcanos  in  Java,  some  of  which  equal  or  surpass  in 
dimensions  even  the  Caldera  of  Palma.  The  latter  may  have  con- 
sisted at  first  of  a  true  crater,  enlarged  afterwards  into  a  caldera  by 
the  partial  destruction  of  a  great  cone ;  but,  if  so,  it  has  certainly 
been  since  modified  by  denudation.  Nor  can  any  geologist  now  de- 
fine how  much  of  the  work  has  been  accomplished  by  aqueous,  and 
how  much  by  volcanic  agency.  The  phenomenon  of  a  river  cutting 
its  channel  through  a  dense  mass  of  ancient  alluvium  formed  during 
oscillations  in  the  level  of  the  land  is  not  confined  to  volcanic  coun- 
tries, and  I  need  not  dwell  here  on  its  interpretation,  but  refer  to 
what  was  said  in  the  7th  chapter.  (See  p.  84.). 

There  remains,  however,  another  question  of  high  theoretical 
interest ;  namely,  whether  the  denudation  was  marine  or  fluviatile. 
It  was  stated  that  the  materials  of  the  great  cone  or  assemblage 
of  cones  in  the  north  of  Palma  are  of  subaerial  origin,  as  proved 
by  the  angularity  of  the  fragments  of  rock  in  the  agglomerates ; 
but  it  may  be  asked,  whether,  when  the  Caldera  was  formed  long 
afterwards,  it  may  not,  like  the  crater  of  St.  Paul's  (fig.  649., 
p.  513.),  have  had  a  communication  with  the  sea,  which  may  have 
entered  by  the  great  Barranco,  and  if,  after  a  period  of  partial 
submergence,  the  island  may  not  then  have  risen  again  to  its  ori- 
ginal altitude.  In  such  a  case  the  retiring  waters  might  leave 
behind  them  a  conglomerate,  partly  of  river-pebbles,  collected  at  the 
points  where  the  torrent  successively  entered  the  sea,  and  partly  of 
stones  rounded  by  the  waves.  The  torrent  may  have  finally  cut  a 
deep  ravine  in  the  gravel  and  associated  lavas  when  the  land  was 
rising  again.  Such  oscillations  of  level,  amounting  to  more  than 
2000  feet,  would  not  be  deemed  improbable  by  any  geologists,  pro- 
vided they  enable  us  to  explain  more  naturally  than  by  any  other 


510  EXTENT  AND  NATURE  OF       [Cn.  XXIX. 

causation,  the  origin  of  the  physical  outlines  of  the  country.  As  to 
the  fact  that  no  marine  shells  have  yet  been  discovered  in  the 
conglomerate,  sufficient  search  has  not  yet  been  made  for  them  to 
entitle  us  to  found  an  argument  on  such  negative  evidence.  At  the 
same  time  I  confess,  that,  having  found  sea-shells  and  bryozoa 
abundantly  in  certain  elevated  marine  conglomerates  in  the  Grand 
Canary,  before  I  visited  Palma,  and  being  unable  to  meet  with  any 
in  the  Barranco  de  las  Angustias,  I  regarded  the  old  gravel  when  I 
was  on  the  spot  as  of  fluviatile  origin.  Such  inferences  are  always 
doubtful  in  the  absence  of  more  positive  data,  and  the  intervention 
of  the  sea  will  unquestionably  account  for  some  phenomena  in  the 
configuration  of  the  Caldera  and  Barranco  more  naturally  than  river 
action.  For  example,  we  have  the  lofty  cliff  E,  fig.  p.  508.  already 
mentioned,  and  c,  f,  map,  p.  498.,  extending  four  or  five  miles  from 
the  Caldera  to  the  sea  on  the  right  bank  of  the  Barranco,  and  no 
cliff  of  corresponding  height  or  structure  on  the  other  bank,  where 
for  miles  towards  the  south-east  there  is  the  platform  F,  fig.  p.  508. 
supporting  several  minor  volcanic  cones.  The  sea  might  be  sup- 
posed to  leave  just  such  a  cliff  as  E,  after  cutting  away  a  portion  of 
the  south-western  extremity  of  the  old  dome-shaped  mountain  in  the 
north  of  Palma,  whereas  a  torrent  or  river  would  leave  a  cliff  of 
similar  structure  and  nearly  equal  height  on  both  banks.  As  to  the 
fact  of  the  old  conglomerate  ascending  an  inclined  plane,  i,  I,  k, 
p.  501.,  from  the  sea-level  to  an  elevation  of  about  1500  feet,  near 
the  entrance  of  the  Caldera,  this  is  by  no  means  conclusive  in  i'avour 
of  fluviatile  action,  although  some  elevated  patches  of  the  same  may 
in  truth  belong  to  an  old  river-bed ;  but  in  South  America  gravel- 
beds  of  marine  origin  have  a  similar  upward  slope,  when  followed 
inland,  and  the  cause  of  such  an  arrangement  has  been  explained  in 
a  satisfactory  manner  by  Mr.  Darwin.* 

Another  argument  in  favour  of  marine  denudation  may  be  derived 
from  that  peculiar  feature  in  the  configuration  of  Palma,  before 
alluded  to,  called  the  pass  of  the  Cumbrecito  (e,  fig.  646.,  p.  501.), 
forming  a  notch  in  the  uppermost  line  of  precipices  surrounding 
the  Caldera.  This  break  divides  the  mountain  called  Alejenado,  d, 
fig.,  p.  501.,  from  the  eastern  wall  c  f,  and  cuts  quite  through  the 
upper  formation  ;  yet  the  range  of  precipice  f,  e,  on  the  eastern  side 
of  the  Caldera  is  continued  uninterruptedly,  and  retains  its  full  height 
of  1500  or  2000  feet  above  its  base,  to  the  southward  of  the  Cum- 
brecito, or  from  e  towards  a,  map,  fig.  642.,  p.  498.  In  this  prolon- 
gation of  the  cliff  for  half  a  mile  southward  beds  of  volcanic  matter 
and  dikes  are  seen,  as  in  the  walls  of  the  Caldera. 

The  indentation  forming  the  pass  of  the  Cumbrecito,  e,  p.  501.,  has 
more  the  appearance  of  an  old  channel,  such  as  a  current  of  water 
may  have  excavated,  than  of  a  rent  or  a  chasm  caused  by  a  fault.  In 
case  of  a  fault  the  lower  formation  would  not  be  persistent  and  unin- 
terrupted across  the  Cumbrecito,  constituting  the  watershed;  but 
would  have  sunk  down  and  have  been  replaced  by  the  upper  basaltic 

*  Geolog.  Observ.,  South  America,  p.  43. 


€H.  XXIX.]  AQUEOUS   EROSION   IN   PALMA.  511 

rocks.  If  we  could  assume  that  the  sea  once  entered  the  Caldera 
here  as  well  as  by  the  great  Barranco,  it  might  have  produced  such 
a  breach  as  ey  and  such  an  extension  of  the  line  of  cliffs  as  that  now 
observable  between  e  and  «,  map,  p.  498.  without  any  corresponding 
cliff  to  the  westward  of  e,  a. 

Yet  we  could  discover  no  elevated  outliers  of  conglomerate  to 
attest  the  supposed  erosion  at  the  Cumbrecito,  which  is  about 
3500  feet  above  the  level  of  the  sea.  It  might  also  be  objected  to 
the  hypothesis  of  marine  denudation  in  Palma,  that  there  are  no 
ranges  of  ancient  sea-cliffs  on  the  external  slopes  of  the  island. 
The  flanks  of  the  mountain,  except  where  it  is  furrowed  by  ravines 
or  broken  by  lateral  cones,  descend  to  the  sea  with  a  uniform 
inclination.  In  reply  to  such  a  remark,  I  may  observe  that  we  do 
not  require  the  submergence  of  the  uppermost  3000  feet  of  the 
old  cone  in  order  to  allow  the  sea  to  enter  both  the  great  Barranco 
and  the  Cumbrecito  and  to  flow  into  the  Caldera.  It  would  be 
enough  to  suppose  the  land  to  sink  down  so  as  to  permit  the  waves 
to  wash  the  base  of  the  basaltic  cliffs  in  the  interior  of  the  Cal- 
dera, and  to  wear  a  passage  through  the  Cumbrecito  where  there 
may  have  been  always  a  considerable  depression  in  the  outline  of 
the  upper  formation.  But  would  not  the  same  waves  which  had 
power  to  form  in  the  Barranco  a  mass  of  conglomerate  800  feet 
thick  have  left  memorials  of  their  beach-action  on  the  external 
slope  of  the  island  ?  No  such  monuments  are  to  be  seen.  It  may 
be  said,  in  explanation,  —  first,  that  cliffs  are  not  so  easily  cut  on  the 
side  of  an  island  towards  which  the  beds  dip  as  on  the  side  from 
which  they  dip ;  secondly,  if  some  small  cliffs  and  sea-beaches  had 
existed,  they  may  have  been  subsequently  buried  under  showers  of 
ashes  and  currents  of  lava  proceeding  from  lateral  cones  during 
eruptions  of  the  same  date  as  those  which  were  certainly  contem- 
poraneous with  the  conglomerate  of  the  great  Barranco. 

On  the  eastern  coast  of  Palma,  about  half  a  mile  from  the  sea,  in 
the  ravine  of  Las  Nieves,  not  far  from  Santa  Cruz,  we  observed  a 
conglomerate  of  well-rounded  pebbles  having  a  thickness  of  100 
feet,  covered  by  successive  beds  of  lava,  also  about  100  feet  thick. 
In  this  instance  the  ancient  gravel  beds  occupy  a  position  very 
analogous  to  the  buried  cone,  s.  P.,  fig.  645.,  p.  500.  When  in  Palma, 
I  conceived  them  to  be  of  fluviatile  origin  ;  but,  whether  marine  or 
freshwater,  it  must  be  admitted  that  the  superposition  of  so  dense  an 
accumulation  of  lavas  to  a  mass  of  conglomerate  100  feet  thick 
shows  how  easily  the  outer  slopes  of  the  island  may  have  been 
denuded  by  the  sea  and  yet  display  no  superficial  signs  of  marine 
denudation,  every  old  beach  or  delta  once  at  the  mouth  of  a  torrent 
being  concealed  under  newer  volcanic  outpourings. 

Since  the  cessation  of  volcanic  action  in  the  north  of  Palma,  the 
most  frequent  eruptions  appear  to  have  taken  place  in  a  line  running 
north  and  south,  from  a  to  Fuencaliente,  map,  p.  498. ;  one  of  the 
volcanos  in  this  range,  called  Yerigojo,  g,  being  no  less  than  6565 
English  feet  high.  The  lavas  descending  from  several  vents  in  this 


512 


ISLAND    OF    ST.  PAUL. 


[CH.  XXIX. 


chain  reach  the  sea  both  on  the  east  and  west  coast,  and  are  many 
of  them  nearly  as  naked  and  barren  of  vegetation  as  when  they  first 
flowed.  The  tendency  in  volcanic  vents  to  assume  a  linear  ar- 
rangement, as  seen  in  the  volcanos  of  the  Andes  and  Java  on  a 
grand  scale,  is  exemplified  by  the  cones  and  craters  of  this  small 
range  in  Palma.  It  has  been  conjectured  that  such  linearity  in  the 
direction  of  superficial  outbreaks  is  connected  with  deep  fissures  in 
the  earth's  crust  communicating  with  a  subjacent  focus  of  subter- 
ranean heat. 

By  discussing  at  so  much  length  the  question  whether  the  sea 
may  or  may  not  have  played  an  important  part  in  enlarging  the 
Caldera  of  Palma,  I  have  been  desirous  at  least  to  show  how  many 
facts  and  observations  are  required  to  explain  the  structure  and 
configuration  of  such  volcanic  islands.  It  may  be  useful  to  cite,  in 
illustration  of  the  same  subject,  the  present  geographical  condition 
of  St.  Paul's  or  Amsterdam  Island,  in  the  Indian  Ocean,  midway 
between  the  Cape  of  Good  Hope  and  Australia. 

Fig.  648. 


Nine-pin 
rock. 


.    Entrance  nearly  dry  at 
**  low  water. 


Map  of  the  Island  of  St.  Paul,  in  the  Indian  Ocean,  lat.  38°  44'  S.,  long.  77°  37'  E., 
surveyed  by  Capt.  Blackwood,  R.N.,  1842. 

In  this  case  the  crater  is  only  a  mile  in  diameter  and  180  feet 
deep,  and  the  surrounding  cliffs  where  loftiest  about  800  feet  high,  so 
that  in  regard  to  size  such  a  cone  and  crater  are  insignificant  when 
compared  to  the  cone  and  Caldera  of  Palma  or  to  such  volcanic 
domes  as  Mounts  Loa  and  Kea  in  the  Sandwich  Islands.  But  the 
Island  of  St.  Paul  exemplifies  a  class  of  insular  volcanos  into  which 


CH.  XXIX.]      ISLAND   OF    ST.    PAUL. — TENERIFFE 

Fig.  649. 


513 


View  of  the  Crater  of  the  Island  of  St.  Paul. 
Fig.  650. 


Side  view  of  the  Island  of  SL  Paul  (N.E.  side).    Nine-pin  rocks  two  miles  distant. 
(Captain  Blackwood.) 

the  ocean  now  enters  by  a  single  passage.  Every  crater  must 
almost  invariably  have  one  side  much  lower  than  all  the  others, 
namely  that  side  towards  which  the  prevailing  winds  never  blow, 
and  to  which,  therefore,  showers  of  dust  and  scoriae  are  rarely 
carried  during  eruptions.  There  will  also  be  one  point  on  this 
windward  or  lowest  side  more  depressed  than  all  the  rest,  by  which 
in  the  event  of  a  partial  submergence  the  sea  may  enter  as  often  as 
the  tide  rises,  or  as  often  as  the  wind  blows  from  that  quarter.  For 
the  same  reason  that  the  sea  continues  to  keep  open  a  single 
entrance  into  the  lagoon  of  an  atoll  or  annular  coral  reef,  it  will  not 
allow  this  passage  into  the  crater  to  be  stopped  up,  but  will  scour  it 
out  at  low  tide,  or  as  often  as  the  wind  changes.  The  channel, 
therefore,  will  always  be  deepened  in  proportion  as  the  island  rises 
above  the  level  of  the  sea,  at  the  rate  perhaps  of  a  few  feet  or  yards 
in  a  century. 

The  crater  of  Vesuvius  in  1822  was  2000  feet  deep ;  and,  if  it 
were  a  half-submerged  cone  like  St.  Paul,  the  excavating  power  of 
the  ocean  might  in  conjunction  with  a  gradual  upheaving  force  give, 
rise  to  a  large  caldera.  Whatever,  therefore,  may  have  been  the 
nature  of  the  forces,  igneous  or  aqueous,  which  have  shaped  out  the 
Val  del  Bove  on  Etna  or  the  deep  abyss  called  the  Caldera  in  the 
north  of  Palma,  we  can  scarcely  doubt  that  many  craters  have  been 
enlarged  into  calderas  by  the  denuding  power  of  the  ocean,  when- 
ever considerable  oscillations  in  the  relative  level  of  land  and  sea 
have  occurred. 

Peak  of  Teneriffe.  —  The  accompanying  view  of  the  Peak,  taken 

LL 


514 


VIEW   OF   PEAK   OF    TENERIFFE.  [CiL  XXIX. 


a        " 
1       8 


A 


!p^ 

-2U>SC 


. 
tsl! 


w 


CH.  XXIX.]  PEAK   OF   TENERIFFE.  515 

from  sketches  made  by  Mr.  Hartung  and  myself  during  our  visit  to 
Teneriffe  in  1854,  will  show  the  manner  in  which  that  lofty  cone  is 
encircled  on  more  than  two  sides  by  what  I  consider  as  the  ruins  of 
an  older  cone,  chiefly  formed  by  eruptions  from  a  summit  which  has 
disappeared.  That  ancient  culminating  point  from  which  one  or 
more  craters  probably  poured  forth  their  lavas  and  ejectamenta  may 
not  have  been  placed  precisely  where  the  present  peak  now  rises, 
and  may  not  have  had  the  same  form,  but  its  position  was  probably 
not  materially  different.  The  great  wall  or  semicircular  range  of 
precipices,  c  c,  surrounding  the  atrium,  b  b,  is  obviously  analogous  to 
the  walls  of  a  Caldera  like  that  of  Palma  ;  but  here  the  cliffs  are 
insignificant  in  dimensions  when  compared  to  those  in  Palma,  being 
in  general  no  more  than  500  feet  high  and  rarely  exceeding  1000 
feet.  The  plain  or  atrium,  b  b,  figs.  651.  and  652.,  lying  at  the  base 
of  the  cliffs,  is  here  called  Las  Canadas,  and  is  covered  with  sand  and 
pumice  thrown  out  from  the  Peak  or  from  craters  on  its  flanks. 
Copious  streams  of  lava,  dd,  have  also  flowed  down  from  lateral 
openings,  especially  from  a  crater  called  the  Chahorra,  f,  fig.  652., 
which  is  not  seen  in  the  view,  fig.  651.,  as  it  is  hidden  by  the  Peak. 
The  last  eruption  was  as  late  as  the  year  1798. 

Fig.  652. 


Guia 


S.W.  N.E. 

Section  through  part  of  Teneriffe,  from  N.E.  to  S.W.     On  a  true  scale;  as  given  in 

Von  Buch's  "  Canary  Islands." 

a.  Peak  of  Teneriffe.  b.  The  Canadas  or  atrium. 

c.  Cliff  bounding  the  atrium.  d.  Modern  lavas. 

/.  Cone  and  crater  of  Chahorra. 

To  what  extent  the  lavas,  dd,  figs.  651.  and  652.,  may  have  nar- 
rowed the  circus  or  atrium,  b,  or  taken  away  from  the  height  of 
the  cliff  c,  no  geologist  can  determine  for  want  of  sections ;  but 
should  the  Peak  and  the  Chahorra  continue  to  be  active  volcanos 
for  ages,  the  new  cone,  #,  might  become  united  with  the  old  one, 
and  the  lava  might  flow  first  from  e  to  c  and  then  from  a  to  c, 
fig.  652.,  so  that  the  slope  might  begin  to  resemble  that  formed  by 
lavas  and  ejectamenta  from  the  summit  a  to  Guia,  on  the  south- 
western side  of  the  cone. 

Madeira. — Every  volcanic  island,  so  far  as  I  have  examined  them, 
varies  from  every  other  one  in  the  details  of  its  geographical  and 
.  geological  structure  so  greatly  that  I  have  no  expectation  of  finding 
any  simple  hypothesis,  like  that  of  "  elevation  craters,"  applicable  to 
all  or  capable  of  explaining  their  origin  and  mode  of  growth.  Few 
islands,  for  example,  resemble  each  other  more  than  Madeira  and 
Palma,  inasmuch  as  both  consist  mainly  of  basaltic  rocks  of  sub- 
aerial  origin,  but,  when  we  compare  them  closely  together,  there  is 
no  end  of  the  points  in  which  they  differ. 

The  oldest  formation  known  in  Madeira  is  of  submarine  volcanic 

LL  2 


516  ISLAND   OF    MADEIRA.  [Cn.  XXIX. 

origin,  and  referable  perhaps  to  the  Miocene  tertiary  epoch.  Tuffs 
and  limestones  containing  marine  shells  and  corals  occur  at  S.  Vi- 
cente on  the  northern  coast,  where  they  rise  to  the  height  of  more 
than  1200  feet  above  the  sea.  They  bear  testimony  to  an  upheaval 
to  that  amount,  at  least,  since  the  commencement  of  volcanic  action 
in  those  parts. 

The  pebbles  in  these  marine  beds  are  well  rounded  and  polished, 
strongly  contrasting  in  that  respect  with  the  angular  fragments  of 
similar  varieties  of  volcanic  rocks  so  frequent  in  the  superimposed 
tuffs  and  agglomerates  formed  above  the  level  of  the  sea. 

The  length  of  Madeira  from  east  to  west  is  about  30  miles,  its 
breadth  from  north  to  south  being  12  miles.  The  annexed  section, 
fig.  653.,  drawn  up  on  a  true  scale  of  heights  and  horizontal 
distances  from  the  observations  of  Mr.  Hartung  and  myself,  will 
enable  the  reader  to  comprehend  some  of  the  points  in  which, 
geologically  considered,  Madeira  resembles  or  varies  from  Palma. 
In  the  central  region,  at  A,  as  well  as  in  the  adjoining  region  on 
each  side  of  it,  are  seen,  as  in  the  centre  of  Palma,  a  great  number 
of  dikes  penetrating  through  a  vast  accumulation  of  ejectamenta,  c. 
Here  also,  as  in  Palma,  we  observe  as  we  recede  from  the  centre 
that  the  dikes  decrease  in  number,  and  beds  of  scoriae,  lapilli, 
agglomerate,  and  tuff  begin  to  alternate  with  stony  lavas,  d  d, 
until  at  the  distance  of  a  mile  or  more  from  the  central  axis  the 
volcanic  mass,  below  fh  and  eg,  consists  almost  exclusively  of 
streams  or  sheets  of  basalt,  with  some  red  partings  of  ochreous 
clay  or  laterite,  probably  ancient  soils.  The  darker  lines  indicate 
the  predominance  of  these  lavas  which  have  flowed  on  the  surface, 
and  which,  besides  basalt,  consist  of  various  kinds  of  trap,  and  in 
some  places  of  trachyte.  The  lighter  tint,  c,  expresses  an  accu- 
mulation of  scoriae,  agglomerate,  and  other  materials,  such  as  may 
have  been  piled  up  in  the  open  air,  in  or  around  the  chief  orifices 
of  eruption,  and  between  volcanic  cones. 

The  Pico  Torres,  A,  more  than  6000  feet  high,  is  one  of  many 
central  peaks,  composed  of  ejected  materials.  By  the  union  of  the 
foundations  of  many  similar  peaks,  ridges  or  mountain  crests  are 
formed,  from  which  the  tops  of  vertical  dikes  project  like  turrets  above 
the  weathered  surface  of  the  softer  beds  of  tuff  and  scoriae.  Hence 
the  broken  and  picturesque  outline,  giving  a  singular  and  romantic 
character  to  the  scenery  of  the  highest  part  of  Madeira.  North  of 
A  is  seen  Pico  Ruivo  (B),  the  most  elevated  peak  in  the  island,  yet 
exceeding  by  a  few  feet  only  the  height  of  Pico  Torres.  It  is 
similar  in  composition,  but  its  uppermost  part,  400  feet  high,  retains 
a  more  perfectly  conical  form,  and  has  a  dike  at  its  summit  with 
streams  of  scoriaceous  lava  adhering  to  its  steep  flanks.  There  are  a 
great  many  such  peaks  east  and  west  of  A,  which  seem  to  be  the 
ruins  of  cones  of  eruption,  the  materials  of  some  at  least  having 
been  arranged  with  a  qua-qua-versal  dip.  Among  these  is  Pico 
Grande,  c,  fig.  655.,  now  half-buried  under  more  modern  lavas 
which  have  flowed  round  it.  It  is  perhaps  owing  to  the  juxta- 
position of  such  a  multitude  of  cones  or  points  of  eruption,  and  the 


Ck.  XXIX.  1 


SECTION   OF   MADEIRA. 


517 


LL  3 


518  FOSSIL   PLANTS   OF    MADEIRA.  [Ce.  XXIX. 

interference  of  their  lavas  along  the  great  east  and  west  line  of  vol- 
canic action,  that  we  find  the  stony  beds  in  the  central  region  between 
e  andyj  fig.  653.,  nearly  horizontal,  or  having  a  dip  of  no  more  than 
from  3  to  5  degrees  instead  of  having  a  very  steep  inclination  like 
those  in  the  walls  of  the  Caldera  of  Palma. 

These  level  or  slightly  inclined  beds  often  form  platforms,  such  as 
that  called  the  Paul  da  Serra  (a,  fig.,  p.  520.).  But  when  we  recede 
from  the  central  axis,  the  lavas  acquire  an  average  slope  of  10 
degrees  on  the  north  (as  between  e  and  g,  fig.  653.),  and  of  15  on  the 
south  between  f  and  h.  Nearer  the  sea  again,  as  at  i  and  L,  where 
the  most  modern  lavas  occur,  the  dip  diminishes  to  5  degrees,  and 
even  to  3^,  as  at  K,  near  Funchal.  In  this  latter  characteristic, 
however  (the  smaller  inclination  of  the  lavas  near  the  sea,  and  their 
association  there  with  modern  cones  of  eruption,  such  as  M,  N,  o), 
there  is  a  strict  analogy  between  Madeira  and  Palma.  Buried  cones 
of  eruption  also  occur  at  many  points,  as  at  p  and  q,  fig.  653.,  which 
have  been  overwhelmed  by  lavas  flowing  from  the  central  region. 
The  aggregate  thickness  of  the  more  solid  basalts  alternating  with 
tuffs  rarely  exceeds  1500  feet ;  but  below  Pico  S.  Antonio,  or  R,  fig., 
p.  517.,  they  attain  a  thickness  of  3000  feet,  being  exposed  to  view  on 
the  sides  of  a  deep  valley  called  the  Curral,  presently  to  be  men- 
tioned. 

As  a  general  rule,  the  lavas  of  Madeira,  whether  vesicular  or  com- 
pact, do  not  constitute  continuous  sheets  parallel  to  each  other. 
When  viewed  in  the  sea-cliffs  in  sections  transverse  to  the  direction 
in  which  they  flowed,  they  vary  greatly  in  thickness,  even  if 
followed  for  a  few  hundred  feet  or  yards,  and  they  usually  thin  out 
entirely  in  less  than  a  quarter  of  a  mile.  In  the  ravines  which 
radiate  from  the  centre  of  the  island,  the  beds  are  more  persistent, 
but  even  here  they  usually  are  seen  to  terminate,  if  followed  for  a 
few  miles ;  their  thickness  also  being  very  variable,  and  sometimes 
increasing  suddenly  from  a  few  feet  to  many  yards. 

I  saw  no  remains  of  fossil  plants  in  any  of  the  red  partings  or 
laterites  above  alluded  to ;  but  Mr.  Smith,  of  Jordanhill,  was  more 
fortunate  in  1840,  having  met  with  the  carbonized  branches  and 
roots  of  shrubs  in  some  red  clays  under  basalt  near  Funchal.  Never- 
theless, Mr.  Hartung  and  I  obtained  satisfactory  evidence  in  the 
northern  part  of  the  island,  in  the  ravine  of  S.  Jorge,  of  the  former 
existence  of  terrestrial  vegetation,  and  consequently  of  the  subaerial 
origin  of  a  large  portion  of  the  lavas  of  Madeira.  At  q  in  the  section 
(fig.  653.)  the  occurrence  of  a  bed  of  impure  lignite,  covered  by  basalt, 
had  long  been  known.  Associated  with  it,  we  observed  several  layers 
of  tuff  and  clay  or  hardened  mud,  in  one  of  which  leaves  of  dicoty- 
ledonous plants  and  of  ferns  abound.  The  latter,  according  to  Mr. 
Charles  J.  F.  Bunbury,  are  referable  to  the  genera  Sphenopteris, 
Adiantum?,  Pecopteris,  and  Woodwardia,  one  of  them  having  the 
peculiar  venation  of  Woodwardia  radicans,  a  species  now  common 
in  Madeira.  Among  the  dicotyledonous  leaves,  some  are  apparently 
of  the  myrtle  family,  the  larger  proportion  having  their  surfaces 


CH.  XXIX.]          CRATER  OF  LAGOA.  519 

smooth  and  unwrinkled,  with  a  somewhat  rigid  and  coriaceous 
texture,  and  with  undivided  or  entire  margins.  "  These  characters," 
observes  Mr.  Bunbur y,  "  belong  to  the  laurel-type,  and  indicate  a 
certain  analogy  between  the  ancient  vegetable  remains  and  the 
modern  forests  of  Madeira,  in  which  laurels  and  other  evergreens 
abound,  with  glossy  coriaceous  and  entire-edged  leaves,  while  below 
them  there  is  an  undergrowth  of  ferns  and  other  plants." 

The  lignite  above  mentioned  and  the  leaf-bed  occur  at  the  height 
of  1000  feet  above  the  level  of  the  sea,  and  are  overlaid  by  super- 
imposed basalts  and  scoriae,  1100  feet  thick,  implying  the  existence 
of  an  ancient  terrestrial  vegetation  long  before  a  large  part  of 
Madeira  had  been  built  up.  The  nature  of  the  tuffs  accompanying 
the  lignite,  together  with  some  agglomerates  in  the  vicinity,  entitles 
us  to  presume  that  near  this  spot  a  series  of  eruptions  once  broke 
out.  Nor  is  it  improbable  that  there  may  have  been  here  the  crater 
of  some  lateral  cone  in  which  the  lignite  and  leaf-bed  accumulated ; 
for,  although  craters  are  remarkably  rare  in  Madeira,  when  we 
consider  how  considerable  is  the  number  of  perfect  cones,  yet  on  the 
mountain  called  Lagoa,  2|-  miles  west  of  Machico,  a  crater  as  perfect 
as  that  of  Astroni  near  Naples  may  be  seen. 

At  the  bottom  of  this  circular  cavity  (fig.  654.),  which  is  about 
150  feet  deep,  is  a  plain  about  500  feet  in  diameter,  having  a  pond 
in  the  middle,  towards  which  the  plain  slopes  gently  from  all  sides. 
Such  ponds  are  often  seen  in  the  interior  of  extinct  craters.  Except 
n  the  middle  it  is  shallow,  and  supports  aquatic  plants.  Many 
eaves  must  also  be  blown  into  it  from  the  surrounding  heights 
vhen  high  winds  prevail,  so  that  a  mass  of  peaty  matter  convertible 
hto  lignite  may  collect  here. 

Fig.  654. 


Crater  of  Lagoa,  2$  miles  west  of  Machico,  Madeira. 

In  this  cut,  taken  from  a  sketch  of  my  own,  the  depth  of  the  crater  may  appear 
too  great,  unless  it  is  borne  in  mind  that  there  are  no  trees  visible,  and  most  of  the 
hushes  are  of  the  Madeira  whortle-berry  ( Vacciniwn  Madeireme)  five  or  six  feet 
high.  Immediately  behind  the  foreground  an  artificial  mound  is  seen  thrown  up 
as  a  fence. 

Had  streams  of  lava  descending  from  greater  heights  entered  this 
Lagoa  crater,  they  would  have  formed  dense  masses  of  compact  rock 

LL  4 


520  CENTRAL  VALLEYS.          [Ce.  XXIX. 

cooling  slowly  under  great  pressure,  like  those  now  incumbent  on 
the  impure  lignite  of  S.  Jorge.  The  dip  of  the  latter  cannot  be 
clearly  determined,  since  it  is  exposed  to  view  for  too  short  a  dis- 
tance ;  and  the  same  may  be  said  of  the  leaf-bed,  part  of  which  may 
be  traced  lower  down  the  ravine.  It  seems,  however,  to  dip  to  the 
north  or  towards  the  sea  conformably  with  the  general  inclination 
of  the  basaltic  and  tufaceous  strata. 

A  deep  valley,  called  the  Curral  (B,  fig.  655.),  surrounded  by 
precipices  from  1500  to  2500  feet  high,  and  by  peaks  of  still  greater 
elevation,  occurs  in  the  middle  of  Madeira.  It  has  been  compared 
by  some  to  a  crater  or  caldera,  for  its  upper  portion  is  situated  in 
the  region  where  dikes  and  ejectamenta  abound.  The  Curral,  how- 
ever, extends,  without  diminishing  in  depth,  to  below  the  region  of 
numerous  dikes,  and  it  lays  open  to  view  all  the  beds  R,  s,  fig.  653. 
Nor  do  the  volcanic  masses  dip  away  in  all  directions  from  the  Curral, 
as  from  a  central  point,  or  from  the  hollow  axis  of  a  cone.  The 
Curral  is  in  fact  one  only  of  three  great  valleys  which  radiate  from 
the  most  mountainous  district,  a  second  depression,  called  the  Serra 
d'Agoa  (D,  fig.  655.),  being  almost  as  deep.  This  cavity  is  also 
drained  by  a  river  flowing  to  the  south ;  while  a  third  valley,  namely, 
that  of  the  Janella,  sends  its  waters  to  the  north.  The  section  alluded 
to  (fig.  655.),  passing  through  part  of  the  axis  of  the  island  in  an  E. 
and  W.  direction,  shows  how  the  Curral  and  Serra  d'Agoa,  B  and  D, 

Fig.  655. 


Section  through  the  central  region  of  Madeira,  from  East  to  West. 


A.  Part  of  the  platform,  called  the  Paul  da  Serra.  B.  Curral ;  a  valley,  3000  feet  deep. 

C.  Pico  Grande.  D.  The  valley  of  the  Serra  d'Agoa. 

are  separated  by  a  narrow  and  lofty  ridge,  c,  part  of  which 
surmounted  by  the  Pico  Grande,  before  mentioned,  nearly  5400  fept 
high.     There  is  no  essential  difference  between  the  shape  of  the 
three  great  valleys  and  many  of  those  in  the  Alps  and  Pyrenees, 
where  the  valley-making  process  can  have  had  no  connection  wijh 
any  superficial  volcanic  action. 

In  the  Alps,  no  doubt,  as  in  other  lofty  chains,  the  formation  |>f 
valleys  has  been  greatly  aided  by  subterranean  movements,  boih 
gradual  and  violent,  and  by  the  dislocation  of  rocks.  The  same  mgy 
be  true  of  Madeira  and  of  almost  every  lofty  volcanic  region ;  but, 
when  we  reflect  that  the  central  heights  A  and  B,  fig.  653.,  are  more 
than  6000  feet  above  the  sea,  and  that  the  waters  flowing  from  them, 
swollen  by  melted  snows,  reach  the  sea  by  a  course  of  not  much 
more  than  6  miles  in  the  case  of  those  draining  the  Curral,  and  by 
nearly  as  short  a  route  in  the  Serra  d'Agoa,  we  shall  be  prepared 
for  almost  any  amount  of  denudation  effected  simply  by  subaerial 
erosion. 


OH.  XXIX.  TRACHYTIC    ROCKS.  521 

The  general  absence  of  water-worn  pebbles  in  the  tuffs  underlying 
the  Madeira  lavas  is  very  striking,  and  contrasts  with  the  frequent 
occurrence  of  gravel-beds  under  so  many  of  the  Auvergne  lavas.  It 
simply  proves  that  Madeira,  like  the  volcanic  mountains  of  Java,  or 
like  Mount  Etna  or  Mona  Loa  in  the  Sandwich  Islands,  could  not,  for 
reasons  before  given  p.  479.,  support  a  single  torrent  so  long  as  erup- 
tions were  frequent  on  its  slopes.  The  period,  therefore,  of  fluviatile 
erosion  must  have  been  subsequent  to  the  formation  of  the  central 
nucleus  of  ejectamenta,  c,  fig.,  p.  517.,  and  of  the  lavas  d,  ibid.  When 
we  infer  that  these  were  of  supramarine  origin  as  far  down  as  the 
line  p,  s,  t,  and  perhaps  lower,  it  follows  that  a  lofty  island,  4000  feet 
or  more  in  height,  must  have  resulted,  even  if  no  upheaval  had  ever 
occurred. 

The  movements  which  upraised  the  marine  deposits  of  San  Vicente 
may  or  may  not  have  extended  over  a  wide  area.  How  far  they 
modified  the  form  of  the  island,  or  added  to  its  height  is  a  fair  sub- 
ject of  speculation ;  and  whether  the  steep  dip  of  the  lavas  seen  in  the 
ravines  intersecting  the  slopes  of  the  mountain,  f  h,  and  e  g,  can  be 
ascribed  to  such  movements.  The  lavas  of  more  modern  date,  near 
Funchal,  may  be  imagined  to  remain  comparatively  horizontal, 
because  they  have  escaped  the  influence  of  disturbing  forces  to 
which  the  older  nucleus  was  exposed.  Without  discussing  this 
point  (so  fully  treated  of  in  reference  to  Palma),  I  may  observe  that 
unquestionably  different  parts  of  Madeira  have  been  formed  in  suc- 
cession. Near  Porto  da  Cruz,  for  example,  on  the  northern  coast, 
trachytes  of  a  grey,  and  trachytic  tuffs  almost  of  a  white  colour,  in 
slightly  inclined  or  almost  horizontal  beds,  have  partially  filled  up 
deep  valleys  previously  excavated  through  the  older  and  inclined 
basaltic  rocks  (dipping  at  an  angle  of  10°  to  the  north),  under 
which  the  leaf-bed  and  lignite  before  mentioned,  fig.  653.,  p.  517., 
lie  buried.  During  the  convulsions  which  accompanied  the  out- 
pouring of  every  newer  series  of  lavas  the  older  rocks  may  have 
been  more  or  less  disturbed  and  tilted,  without  destroying  the 
general  form  of  the  old  dome-shaped  mountain  supposed  by  us  to 
have  been  the  result  of  repeated  eruptions  from  the  central  vents. 

The  locality  just  referred  to  of  Porto  da  Cruz  exemplifies,  not 
only  the  long  intervals  of  time  which  separated  the  outflowing  of 
distinct  sets  of  lavas,  but  also  the  precedence  of  the  basaltic  to 
the  trachytic  outpourings.  So  also  on  the  northern  slope  of 
Madeira,  I  observed  between  the  Jardim  and  Pico  Bodes,  situated 
in  a  direct  line  about  six  miles  north-west  of  Funchal,  a  well- 
marked  series  of  trachytic  rocks  of  considerable  thickness  occu- 
pying the  highest  geological  position.  They  consist  of  white  and 
grey  trachytes,  occurring  at  points  varying  from  2500  to  3500  feet 
above  the  sea.  Their  position  may  be  understood  by  supposing 
them  to  constitute  the  uppermost  beds  represented  at  h  in  the 
section,  fig.  653.,  p.  517.,  and  on  the  slope  above  h.  The  doctrine, 
therefore,  that  in  each  series  of  volcanic  eruptions  the  trachytic 
lavas  flow  out  first,  and  after  them  the  basaltic  kinds  (see  p.  526.), 


522  LAVAS   OP    MADEIRA.  [Cn.  XXIX. 

is  by  no  means  borne  out  in  Madeira,  although  some  of  the  newest 
currents,  like  those  at  the  foot  of  the  cones  M,  N,  o,  fig.  653.,  are 
basaltic. 

I  may  here  allude  to  another  feature  in  the  mineralogical 
structure  of  Madeira,  namely,  that  most  commonly  the  uppermost 
of  all  the  volcanic  rocks,  when  we  ascend  to  heights  of  1200  feet 
or  more  above  the  sea,  consist  of  compact  felspathic  trap,'  with 
much  olivine,  separating  into  spheroidal  masses  several  feet  in 
diameter,  especially  when  some  of  the  contained  iron  has  become 
more  highly  oxidated  in  the  atmosphere.  M.  Delesse,  after  ex- 
amining my  specimens,  informs  me  that  in  France  they  would  call 
this  rock  basalt,  although  it  is  often  without  augite  and  simply  a 
mixture  of  blackish  green  felspar  with  olivine.  Whatever  name  we 
assign  to  it,  the  superficial  envelope  of  the  island,  not  only  in  the  line 
of  section  followed  in  fig.  653.,  p.  517.,  but  also  very  generally,  may 
be  said  to  consist  of  this  trap,  except  near  the  sea,  where  basalts 
occur  which  have  not  the  same  spheroidal  structure. 

Among  other  indications  of  a  considerable  difference  of  age,  even 
in  the  superficial  volcanic  formations  of  Madeira,  I  may  remark  that 
many  of  the  central  peaks,  such  as  A,  fig.  653.,  seem  to  be  the  mere 
skeletons  of  cones  of  eruption;  whereas  the  forms  of  the  more 
modern  cones,  such  as  M,  N,  o,  are  regular,  and  have  no  protruding 
dikes  on  their  summits  or  flanks.  The  newest  lavas  also  in 
Madeira  have,  in  one  district  at  least,  a  singularly  recent  aspect  as 
compared  to  those  of  older  date,  which  are  decomposed  superficially 
often  to  the  depth  of  several  feet  or  yards.  I  allude  to  the  lava 
currents  near  Port  Moniz,  one  of  which  is  as  rough  and  bristling 
as  are  some  streams  before  alluded  to  in  Palma  (p.  512.)  of  his- 
torical date.  I  am  indebted  to  Mr.  Hartung  for  the  annexed 
drawing  of  a  lava  at  Port  Moniz,  which  I  did  not  visit  myself. 

Fig.  656. 


Surface  of  lava  near  Port  Moniz,  N.W.  point  of  Madeira ;  from  a  drawing  by  M.  Hartung 
a.  Channel  traversing  the  lava. 

It  is  traversed  by  a  channel,  a,  like  one  of  those  already  described, 
p.  507.  For  how  long  a  period  such  characters  may  be  retained  is 
uncertain,  so  much  does  this  depend  on  the  mineral  composition 
of  the  rock.  Some  of  the  lavas  of  Auvergne  of  prehistorical  date 
and  certainly  of  high  antiquity,  are  almost  as  rugged ;  so  that 
this  freshness  of  aspect  is  only  a  probable  indication  of  a  relatively 
modern  origin. 


CH.  XXX.]        TESTS   OF   AGE    OF   VOLCANIC   BOCKS.  523 


CHAPTER  XXX. 

ON  THE  DIFFERENT  AGES  OF  THE  VOLCANIC  ROCKS. 

Tests  of  relative  age  of  volcanic  rocks  —  Tests  by  superposition  and  intrusion — 
Dike  of  Quarrington  Hill,  Durham  —  Test  by  alteration  of  rocks  in  contact  — 
Test  by  organic  remains  —  Test  of  age  by  mineral  character — Test  by  included 
fragments — Volcanic  rocks  of  the  Post- Pliocene  period  —  Basalt  of  the  Bay 
of  Trezza  in  Sicily — Post-Pliocene  volcanic  rocks  near  Naples— Dikes  of  Somma 
—  Igneous  formations  of  the  Newer  Pliocene  period  —  Val  di  Noto  in  Sicily. 

HAVING  referred  the  sedimentary  strata  to  a  long  succession  of 
geological  periods,  we  have  now  to  consider  how  far  the  volcanic 
formations  can  be  classed  in  a  similar  chronological  order.  The 
tests  of  relative  age  in  this  class  of  rocks  are  four:  —  1st,  super- 
position and  intrusion,  with  or  without  alteration  of  the  rocks  in 
contact ;  2nd,  organic  remains ;  3rd,  mineral  characters ;  4th,  in- 
cluded fragments  of  older  rocks. 

Tests  by  superposition,  fyc.  —  If  a  volcanic  rock  rest  upon  an 
aqueous  deposit,  the  former  must  be  the  newest  of  the  two,  but  the 
like  rule  does  not  hold  good  where  the  aqueous  formation  rests  upon 
the  volcanic,  for  melted  matter,  rising  from  below,  may  penetrate  a 
sedimentary  mass  without  reaching  the  surface,  or  may  be  forced  in 
conformably  between  two  strata,  as  b  at  D  in  the  annexed  figure 
(fig.  656.),  after  which  it  may  cool  down  and  consolidate.  Super- 
Fig.  657. 


position,  therefore,  is  not  of  the  same  value  as  a  test  of  age  in  the 
unstratified  volcanic  rocks  as  in  fossiliferous  formations.  We  can 
only  rely  implicitly  on  this  test  where  the  volcanic  rocks  are 
contemporaneous,  not  where  they  are  intrusive.  Now,  they  are  said 
to  be  contemporaneous  if  produced  by  volcanic  action  which  was 
going  on  simultaneously  with  the  deposition  of  the  strata  with 
which  they  are  associated.  Thus  in  the  section  at  D  (fig.  656.),  we 
may  perhaps  ascertain  that  the  trap  b  flowed  over  the  fossiliferous 
bed  c,  and  that,  after  its  consolidation,  a  was  deposited  upon  it,  a 
and  c  both  belonging  to  the  same  geological  period.  But  if  the 
stratum  a  be  altered  by  b  at  the  point  of  contact,  we  must  then 
conclude  the  trap  to  have  been  intrusive,  or  if,  in  pursuing  b  for 


524 


TESTS   OF   RELATIVE   AGE 


[Cn.  XXX. 


Fig.  658. 


some  distance,  we  find  at  length  that  it  cuts  through  the  stratum  «, 
and  then  overlies  it  as  at  E. 

We  may,  however,  be  easily  deceived  in  supposing  a  volcanic  rock 
to  be  intrusive,  when  in  reality  it  is  contemporaneous  ;  for  a  sheet 
of  lava,  as  it  spreads  over  the  bottom  of  the  sea,  cannot  rest  every 
where  upon  the  same  stratum,  either  because  these  have  been  de- 
nuded, or  because,  if  newly  thrown  down,  they  thin  out  in  certain 
places,  thus  allowing  the  lava  to  cross  their  edges.  Besides  the 
heavy  igneous  fluid  will  often,  as  it  moves  along,  cut  a  channel  into 

beds  of  soft  mud  and  sand.  Suppose 
the  submarine  lava  F,  fig.  658.,  to  have 
come  in  contact  in  this  manner  with 
the  strata  a,  b,  c,  and  that  after  its 
consolidation  the  strata  d,  e,  are  thrown 
down  in  a  nearly  horizontal  position, 
yet  so  as  to  lie  un  conformably  to  F,  the 
appearance  of  subsequent  intrusion  will 
here  be  complete,  although  the  trap  is  in  fact  contemporaneous. 
We  must  not,  therefore,  hastily,  infer  that  the  rock  F  is  intrusive, 
unless  we  find  the  strata  d,  e,  or  c,  to  have  been  altered  at  their 
junction,  as  if  by  heat. 

When  trap  dikes  were  described  in  the  preceding  chapter,  they 
were  shown  to  be  more  modern  than  all  the  strata  which  they 
traverse.  A  basaltic  dike  at  Quarrington  Hill  near  Durham,  passes 
through  coal-measures,  the  strata  of  which  are  inclined,  and  shifted 
so  that  those  on  the  north  side  of  the  dike  are  24  feet  above  the 
level  of  the  corresponding  beds  on  the  south  side  (see  section, 
fig.  659.).  But  the  horizontal  beds  of  overlying  Red  Sandstone  and 

Fig.  659. 
Magnesian  limestone. 


Coal.  Dike.  Coal.  N 

Section  at  Quarrington  Hill,  east  of  Durham.    (Sedgwick.) 
a.  Magnesian  Limestone  (Permian).  b.  Lower  New  Red  Sandstone. 

c.  Coal  strata. 

Magnesian  Limestone  are  not  cut  through  by  the  dike.  Now  here 
the  coal-measures  were  not  only  deposited,  but  had  subsequently 
been  disturbed,  fissured,  and  shifted,  before  the  fluid  trap  now 
forming  the  dike  was  introduced  into  a  rent.  It  is  also  clear  that 
some  of  the  upper  edges  of  the  coal  strata,  together  with  the  upper 
part  of  the  dike,  had  been  subsequently  removed  by  denudation 
before  the  lower  New  Red  Sandstone  and  Magnesian  Limestone 
were  superimposed.  Even  in  this  case,  however,  although  the  date 


'Cn.  XXX.]  OF   VOLCANIC   ROCKS.  525 

of  the  volcanic  eruption  is  brought  within  narrow  limits,  it  cannot 
be  defined  with  precision ;  it  may  have  happened  either  at  the  close 
of  the  Carboniferous  period,  or  early  in  that  of  the  Lower  New 
Red  Sandstone,  or  between  these  two  periods,  when  the  state  of  the 
animate  creation  and  the  physical  geography  of  Europe  were  gra- 
dually changing  from  the  type  of  the  Carboniferous  era  to  that  of 
the  Permian. 

The  test  of  age  by  superposition  is  strictly  applicable  to  all  stra- 
tified volcanic  tuffs,  according  to  the  rules  already  explained  in  the 
case  of  other  sedimentary  deposits.  (See  p.  97.) 

Test  of  age  by  organic  remains.  —  We  have  seen  how,  in  the 
vicinity  of  active  volcanos,  scoriae,  pumice,  fine  sand,  and  fragments 
of  rock  are  thrown  up  into  the  air,  and  then  showered  down  upon  the 
land,  or  into  neighbouring  lakes  or  seas.  In  the  tuffs  so  formed 
shells,  corals,  or  any  other  durable  organic  bodies  which  may  happen 
to  be  strewed  over  the  bottom  of  a  lake  or  sea  will  be  embedded,  and 
thus  continue  as  permanent  memorials  of  the  geological  period  when 
the  volcanic  eruption  occurred.  Tufaceous  strata  thus  formed  in  the 
neighbourhood  of  Vesuvius,  Etna,  Stromboli,  and  other  volcanos  now 
active  in  islands  or  near  the  sea,  may  give  information  of  the  relative 
age  of  these  tuffs  at  some  remote  future  period  when  the  fires  of  these 
mountains  are  extinguished.  By  evidence  of  this  kind  we  can 
establish  a  coincidence  in  age  between  volcanic  rocks  and  the  dif- 
ferent primary,  secondary,  and  tertiary  fossiliferous  strata. 

The  tuffs  alluded  to  may  not  always  be  marine,  but  may  include, 
in  some  places,  freshwater  shells  ;  in  others,  the  bones  of  terrestrial 
quadrupeds.  The  diversity  of  organic  remains  in  formations  of  this 
nature  is  perfectly  intelligible,  if  we  reflect  on  the  wide  dispersion  of 
ejected  matter  during  late  eruptions,  such  as  that  of  the  volcano  of 
Coseguina,  in  the  province  of  Nicaragua,  January  19.  1835.  Hot 
cinders  and  fine  scoriae  were  then  cast  up  to  a  vast  height,  and 
covered  the  ground  as  they  fell  to  the  depth  of  more  than  10  feet, 
and  for  a  distance  of  8  leagues  from  the  crater  in  a  southerly  direc- 
tion. Birds,  cattle,  and  wild  animals  were  scorched  to  death  in 
great  numbers,  and  buried  in  ashes.  Some  volcanic  dust  fell  at 
Chiapa,  upwards  of  1200  miles,  not  to  leeward  of  the  volcano  as 
might  have  been  anticipated,  but  to  windward,  a  striking  proof  of 
a  counter  current  in  the  upper  region  of  the  atmosphere  ;  and  some 
on  Jamaica,  about  700  miles  distant  to  the  north-east.  In  the  sea, 
also,  at  the  distance  of  1100  miles  from  the  point  of  eruption,  Cap- 
tain Eden  of  the  Conway  sailed  40  miles  through  floating  pumice, 
among  which  were  some  pieces  of  considerable  size.* 

Test  of  age  by  mineral  composition.  —  As  sediment  of  homo- 
geneous composition,  when  discharged  from  the  mouth  of  a  large 
river,  is  often  deposited  simultaneously  over  a  wide  space,  so  a  par- 
ticular kind  of  lava,  flowing  from  a  crater  during  one  eruption,  may 
spread  over  an  extensive  area ;  as  in  Iceland  in  1783,  when  the 

*  Caldcleugh,  Phil.  Trans.  1836.  p.  27. 


526        RELATIVE  AGES  OF  VOLCANIC  ROCKS.   [Cu.  XXX. 

melted  matter,  pouring  from  Skaptar  Jokul,  flowed  in  streams  in 
opposite  directions,  and  caused  a  continuous  mass  the  extreme  points 
of  which  were  90  miles  distant  from  each  other.  This  enormous 
current  of  lava  varied  in  thickness  from  100  feet  to  600  feet,  and  in 
breadth  from  that  of  a  narrow  river  gorge  to  15  miles.*  Now,  if 
such  a  mass  should  afterwards  be  divided  into  separate  fragments  by 
denudation,  we  might  still  perhaps  identify  the  detached  portions  by 
their  similarity  in  mineral  composition.  Nevertheless,  this  test  will 
not  always  avail  the  geologist ;  for,  although  there  is  usually  a  pre- 
vailing character  in  lava  emitted  during  the  same  eruption,  and  even 
in  the  successive  currents  flowing  from  the  same  volcano,  still,  in 
many  cases,  the  different  parts  even  of  one  lava-stream,  or,  as  before 
stated,  of  one  continuous  mass  of  trap,  vary  much  in  mineral  com- 
position and  texture. 

In  Auvergne,  the  Eifel,  and  other  countries  where  trachyte  and 
basalt  are  both  present,  the  trachytic  rocks  are  for  the  most  part 
older  than  the  basaltic.  These  rocks  do,  indeed,  sometimes  alternate 
partially,  as  in  the  volcano  of  Mont  Dor,  in  Auvergne ;  and  we  have 
seen  that  in  Madeira  trachytic  rocks  may  overlie  an  older  basaltic 
series  (p.  521.) ;  but  the  great  mass  of  trachyte  occupies  more  generally 
perhaps  an  inferior  position,  and  is  cut  through  and  overflowed  by 
basalt.  It  can  by  no  means  be  inferred  that  trachyte  predominated  at 
one  period  of  the  earth's  history  and  basalt  at  another,  for  we  know 
that  trachytic  lavas  have  been  formed  at  many  successive  periods, 
and  are  still  emitted  from  many  active  craters ;  but  it  seems  that  in 
each  region,  where  a  long  series  of  eruptions  have  occurred,  the  more 
felspathic  lavas  have  been  first  emitted,  and  the  escape  of  the  more 
augitic  kinds  has  followed.  The  hypothesis  suggested  by  Mr.  Scrope 
may,  perhaps,  afford  a  solution  of  this  problem.  The  minerals,  he 
observes,  which  abound  in  basalt  are  of  greater  specific  gravity  than 
those  composing  the  felspathic  lavas  ;  thus,  for  example,  hornblende, 
augite,  and  olivine  are  each  more  than  three  times  the  weight  of 
water ;  whereas  common  felspar,  albite,  and  Labrador  felspar  have 
each  scarcely  more  than  2-|  times  the  specific  gravity  of  water ;  and 
the  difference  is  increased  in  consequence  of  there  being  much  more 
iron  in  a  metallic  state  in  basalt  and  greenstone  than  in  trachyte  and 
other  felspathic  lavas  and  trap  rocks.  If,  therefore,  a  large  quantity 
of  rock  be  melted  up  in  the  bowels  of  the  earth  by  volcanic  heat,  the 
denser  ingredients  of  the  boiling  fluid  may  sink  to  the  bottom,  and 
the  lighter  remaining  above  would  in  that  case  be  first  propelled  up- 
wards to  the  surface  by  the  expansive  power  of  gases.  Those  ma- 
terials, therefore,  which  occupy  the  lowest  place  in  the  subterranean 
reservoir  will  always  be  emitted  last,  and  take  the  uppermost  place 
on  the  exterior  of  the  earth's  crust. 

Test  by  included  fragments.  —  We  may  sometimes  discover  the 
relative  age  of  two  trap  rocks,  or  of  an  aqueous  deposit  and  the  trap 
on  which  it  rests,  by  finding  fragments  of  one  included  in  the  other, 

*  See  Principles,  Index,  "  Skaptar  JokuL" 


C«.  XXX.]  POST-PLIOCENE   VOLCANIC   ROCKS.  527 

in  cases  such  as  those  before  alluded  to,  where  the  evidence  of  super- 
position alone  would  be  insufficient.  It  is  also  not  uncommon  to  find 
a  conglomerate  almost  exclusively  composed  of  rolled  pebbles  of  trap, 
associated  with  some  fossiliferous  stratified  formation  in  the  neigh- 
bourhood of  massive  trap.  If  the  pebbles  agree  generally  in  mineral 
character  with  the  latter,  we  are  then  enabled  to  determine  its  rela- 
tive age  by  knowing  that  of  the  fossiliferous  strata  associated  with 
the  conglomerate.  The  origin  of  such  conglomerates  is  explained  by 
observing  the  shingle  beaches  composed  of  trap  pebbles  in  modern 
volcanic  islands,  or  at  the  base  of  Etna. 

Post-Pliocene  Period  (including  the  Recent).  —  I  shall  now  select 
examples  of  contemporaneous  volcanic  rocks  of  successive  geological 
periods,  to  show  that  igneous  causes  have  been  in  activity  in  all  past 
ages  of  the  world,  and  that  they  have  been  ever  shifting  the  places 
where  they  have  broken  out  at  the  earth's  surface. 

One  portion  of  the  lavas,  tuffs,  and  trap-dikes  of  Etna,  Vesuvius, 
and  the  Island  of  Ischia  has  been  produced  within  the  historical  era ; 
another,  and  a  far  more  considerable  part,  originated  at  times  imme- 
diately antecedent,  when  the  waters  of  the  Mediterranean  were 
already  inhabited  by  the  existing  species  of  testacea.  The  southern 
and  eastern  flanks  of  Etna  are  skirted  by  a  fringe  of  alternating  sedi- 
mentary and  volcanic  deposits,  of  submarine  origin,  as  at  Aderno, 
Trezza,  and  other  places.  Of  sixty-five  species  of  fossil  shells  which 
I  procured  in  1828  from  this  formation,  near  Trezza,  it  was  impos- 
sible to  distinguish  any  one  from  species  now  living  in  the  neigh- 
bouring sea. 

The  Cyclopian  Islands,  called  by  the  Sicilians  Dei  Faraglioni,  in 
the  sea-cliffs  of  which  these  beds  of  clay,  tuff,  and  associated  lava  are 
laid  open  to  view,  are  situated  in  the  Bay  of  Trezza,  and  may  be  re- 
Fig.  660. 


View  of  the  Isle  of  Cyclops  in  the  Bay  of  Trezza.* 

garded  as  the  extremity  of  a  promontory  severed  from  the  mam  land. 
Here  numerous  proofs  are  seen  of  submarine  eruptions,  by  which  the 

*  This  view  of  the  Isle  of  Cyclops  is  from  an  original  drawing  by  my  friend 
the  late  Captain  Basil  Hall,  K.N. 


528 


VOLCANIC    ROCKS   OF 


[Cn.  XXX. 


argillaceous  and  sandy  strata  were  invaded  and  cut  through,  and  tu- 
faceous  breccias  formed.  Inclosed  in  these  breccias  are  many  angular 
and  hardened  fragments  of  laminated  clay  in  different  states  of  alter- 
ation by  heat,  and  intermixed  with  volcanic  sands. 

The  loftiest  of  the  Cyclopian  islets,  or  rather  rocks,  is  about  200 
feet  in  height,  the  summit  being  formed  of  a  mass  of  stratified  clay, 
the  laminae  of  which  are  occasionally  subdivided  by  thin  arenaceous 
layers.  These  strata  dip  to  the  N.W.,  and  rest  on  a  mass  of  columnar 
lava  (see  fig.  660.)  in  which  the  tops  of  the  pillars  are  weathered, 
and  so  rounded  as  to  be  often  hemispherical.  In  some  places  in  the 
adjoining  and  largest  islet  of  the  group,  which  lies  to  the  north-east- 
ward of  that  represented  in  the  drawing  (fig.  660.),  the  overlying 
clay  has  been  greatly  altered  and  hardened  by  the  igneous  rock,  and 
occasionally  contorted  in  the  most  extraordinary  manner ;  yet  the 
lamination  has  not  been  obliterated,  but,  on  the  contrary,  rendered 
much  more  conspicuous,  by  the  indurating  process. 

In  the  annexed  woodcut  (fig.  661.)  I  have  represented  a  portion  of 
the  altered  rock,  a  few  feet  square,  where  the  alternating  thin  laminse 

of  sand  and  clay  have  put 


Fig.  661. 


which 


on  the  appearance 
we  often  observe  in  some 
of  the  most  contorted  of  the 
metamorphic  schists. 

A  great  fissure,  running 
from  east  to  west,  nearly 
divides  this  larger  island 
into  two  parts,  and  lays  open 
its  internal  structure.  In 
the  section  thus  exhibited, 
a  dike  of  lava  is  seen,  first 
cutting  through  an  older 
mass  of  lava,  and  then  pene- 
trating the  superincumbent 
tertiary  strata.  In  one  place 
the  lava  ramifies  and  ter- 
minates in  thin  veins,  from 
a  few  feet  to  a  few  inches  in 
thickness.  (See  fig.  662.). 

The  arenaceous  laminae 
are  much  hardened  at  the 
point  of  contact,  and  the 
clays  are  converted  into  sili- 
ceous schist.  In  this  island 
the  altered  rocks  assume  a 
honeycombed  structure  on  their  weathered  surface,  singularly  con- 
trasted with  the  smooth  and  even  outline  which  the  same  beds  present 
in  their  usual  soft  and  yielding  state. 

The  pores  of  the  lava  are  sometimes  coated,  or  entirely  filled,  with 
carbonate  of  lime,  and  with  a  zeolite  resembling  analcime,  which  has 


Contortions  of  strata  in  the  largest  of  the  Cyclopian 
Islands. 


CnrXXX.]  THE   POST-PLIOCENE   PERIOD. 

Fig.  662. 


529 


a. 
Lava. 


Altered. 


b. 
Clay.    Lava.     Clay. 

Post- Pliocene  strata  invaded  by  lava,  Isle  of  Cyclops  (horizontal  section). 
a.  Lava.  b.  Laminated  clay  and  sand.  c.  The  same  altered. 

been  called  cyclopite.  The  latter  mineral  has  also  been  found  in 
small  fissures  traversing  the  altered  marl,  showing  that  the  same  cause 
which  introduced  the  minerals  into  the  cavities  of  the  lava,  whether 
we  suppose  sublimation  or  aqueous  infiltration,  conveyed  it  also  into 
the  open  rents  of  the  contiguous  sedimentary  strata. 

Post-Pliocene  formations  near  Naples.  —  I  have  traced  in  the 
"  Principles  of  Geology "  the  history  of  the  changes  which  the  vol- 
canic region  of  Campania  is  known  to  have  undergone  during  the 
last  2000  years.  The  aggregate  effect  of  igneous  operations  during 
that  period  is  far  from  insignificant,  comprising  as  it  does  the  forma- 
tion of  the  modern  cone  of  Vesuvius  since  the  year  79,  and  the  pro- 
duction of  several  minor  cones  in  Ischia,  together  with  that  of 
Monte  Nuovo  in  the  year  1538.  Lava-currents  have  also  flowed 
upon  the  land  and  along  the  bottom  of  the  sea-—  volcanic  sand, 
pumice,  and  scoriae  have  been  showered  down  so  abundantly  that 
whole  cities  were  buried  —  tracts  of  the  sea  have  been  filled  up  or 
converted  into  shoals  —  and  tufaceous  sediment  has  been  transported 
by  rivers  and  land-floods  to  the  sea.  There  are  also  proofs,  during 
the  same  recent  period,  of  a  permanent  alteration  of  the  relative 
levels  of  the  land  and  sea  in  several  places,  and  of  the  same  tract 
having,  near  Puzzuoli,  been  alternately  upheaved  and  depressed  to 
the  amount  of  more  than  20  feet.  In  connection  with  these  convul- 
sions, there  are  found,  on  the  shores  of  the  Bay  of  Baiae,  recent 
tufaceous  strata,  filled  with  articles  fabricated  by  the  hands  of  man, 
and  mingled  with  marine  shells. 

It  was  also  stated  in  this  work  (p.  119.),  that  when  we  examine 
this  same  region,  it  is  found  to  consist  largely  of  tufaceous  strata,  of 
a  date  anterior  to  human  history  or  tradition,  which  are  of  such 
thickness  as  to  constitute  hills  from  500  to  more  than  2000  feet  in 

MM 


530  VOLCANIC   ROCKS   OF  [Cn.  XXX. 

height.  These  post-pliocene  strata,  containing  recent  marine  shells, 
alternate  with  distinct  currents  and  sheets  of  lava  which  were  of 
contemporaneous  origin  ;  and  we  find  that  in  Vesuvius  itself,  the 
ancient  cone  called  Somma  is  of  far  greater  volume  than  the  modern 
cone,  and  is  intersected  by  a  far  greater  number  of  dikes.  In  con- 
trasting this  ancient  part  of  the  mountain  with  that  of  modern  date, 
one  principal  point  of  difference  is  observed ;  namely,  the  greater 
frequency  in  the  older  cone  of  fragments  of  altered  sedimentary 
rocks  ejected  during  eruptions.  We  may  easily  conceive  that  the 
first  explosions  would  act  with  the  greatest  violence,  rending  and 
shattering  whatever  solid  masses  obstructed  the  escape  of  lava  and 
the  accompanying  gases,  so  that  great  heaps  of  ejected  pieces  of  rock 
would  naturally  occur  in  the  tufaceous  breccias  formed  by  the  earliest 
eruptions.  But  when  a  passage  had  once  been  opened,  and  an 
habitual  vent  established,  the  materials  thrown  out  would  consist  of 
liquid  lava,  which  would  take  the  form  of  sand  and  scoriae,  or  of 
angular  fragments  of  such  solid  lavas  as  may  have  choked  up  the 
vent. 

Among  the  fragments  which  abound  in  the  tufaceous  breccias  of 
Somma,  none  are  more  common  than  a  saccharoid  dolomite,  supposed 
to  have  been  derived  from  an  ordinary  limestone  altered  by  heat  and 
volcanic  vapours. 

Carbonate  of  lime  enters  into  the  composition  of  so  many  of  the 
simple  minerals  found  in  Somma,  that  M.  Mitscherlich,  with  much 
probability,  ascribes  their  great  variety  to  the  action  of  the  volcanic 
heat  on  subjacent  masses  of  limestone. 

Dikes  of  Somma.  —  The  dikes  seen  in  the  great  escarpment  which 
Somma  presents  towards  the  modern  cone  of  Vesuvius  are  very 
numerous.  They  are  for  the  most  part  vertical,  and  traverse  at 
right  angles  the  beds  of  lava,  scorise,  volcanic  breccia,  and  sand,  of 
which  the  ancient  cone  is  composed.  They  project  in  relief  several 
inches  or  sometimes  feet,  from  the  face  of  the  cliff,  being  extremely 
compact,  and  less  destructible  than  the  intersected  tuffs  and  porous 
lavas.  In  vertical  extent  they  vary  from  a  few  yards  to  500  feet, 
and  in  breadth  from  1  to  12  feet.  Many  of  them  cut  all  the  inclined 
beds  in  the  escarpment  of  Somma  from  top  to  bottom,  others  stop 
short  before  they  ascend  above  half  way,  and  a  few  terminate  at  both 
ends,  either  in  a  point  or  abruptly.  In  mineral  composition  they 
scarcely  differ  from  the  lavas  of  Somma,  the  rock  consisting  of  a 
base  of  leucite  and  augite,  through  which  large  crystals  of  augite 
and  some  of  leucite  are  scattered.*  Examples  are  not  rare  of  one 
dike  cutting  through  another,  and  in  one  instance  a  shift  or  fault  is 
seen  at  the  point  of  intersection. 

In  some  cases,  however,  the  rents  seem  to  have  been  filled  laterally, 
when  the  walls  of  the  crater  had  been  broken  by  star-shaped  cracks, 
as  seen  in  the  accompanying  wood-cut  (fig.  663.).  But  the  shape  of 

*  L.  A.  Necker,  Mem.  de  la  Soc.  de  Phys.  et  d'Hist.  Nat.  de  Geneve,  torn,  il 
part  i.  Nov.  1822. 


Ofl.  XXX.]  THE   POST-PLIOCENE    PERIOD.  631 

Fig.  663. 


Dikes  or  veins  at  the  Punto  del  Nasone  on  Somma.    (Necker.*) 

these  rents  is  an  exception  to  the  general  rule ;  for  nothing  is  more 
remarkable  than  the  usual  parallelism  of  the  opposite  sides  of  the 
dikes,  which  correspond  almost  as  regularly  as  the  two  opposite  faces 
of  a  wall  of  masonry.  This  character  appears  at  first  the  more  in- 
explicable, when  we  consider  how  jagged  and  uneven  are  the  rents 
caused  by  earthquakes  in  masses  of  heterogeneous  composition,  like 
those  composing  the  cone  of  Somma.  In  explanation  of  this  phe- 
nomenon, M.  Necker  refers  us  to  Sir  W.  Hamilton's  account  of  an 
eruption  of  Vesuvius  in  the  year  1779,  who  records  the  following 
facts :  —  "  The  lavas,  when  they  either  boiled  over  the  crater,  or 
broke  out  from  the  conical  parts  of  the  volcano,  constantly  formed 
channels  as  regular  as  if  they  had  been  cut  by  art  down  the  steep 
part  of  the  mountain  ;  and,  whilst  in  a  state  of  perfect  fusion,  con- 
tinued their  course  in  those  channels,  which  were  sometimes  full  to 
the  brim,  and  at  other  times  more  or  less  so,  according  to  the  quantity 
of  matter  in  motion. 

These  channels,  upon  examination  after  an  eruption,  I  have 
found  to  be  in  general  from  two  to  five  or  six  feet  wide,  and  seven 
or  eight  feet  deep.  They  were  often  hid  from  the  sight  by  a 
quantity  of  scoriae  that  had  formed  a  crust  over  them ;  and  the  lava, 
having  been  conveyed  in  a  covered  way  for  some  yards,  came  out 
fresh  again  into  an  open  channel.  After  an  eruption,  I  have 
walked  in  some  of  those  subterraneous  or  covered  galleries,  which 
were  exceedingly  curious,  the  sides,  top,  and  bottom  being  worn 
perfectly  smooth  and  even  in  most  parts,  by  the  violence  of  the 
currents  of  the  red-hot  lavas  which  they  had  conveyed  for  many 
weeks  successively."  f 

Now,  the  walls  of  a  vertical  fissure,  through  which  lava  has 
ascended  in  its  way  to  a  volcanic  vent,  must  have  been  exposed  to 
the  same  erosion  as  the  sides  of  the  channels  before  adverted  to. 

*  From  a  drawing  of  M.  Necker, -in      f  Phil.  Trans.,  vol.  hoc,  1780. 
Mem.  above  cited. 

MM  2 


532  POST-PLIOCENE  VOLCANIC   ROCKS.  [Cn.  XXX. 

The  prolonged  and  uniform  friction  of  the  heavy  fluid,  as  it  is 
forced  and  made  to  flow  upwards,  cannot  fail  to  wear  and  smooth 
down  the  surfaces  on  which  it  rubs,  and  the  intense  heat  must  melt 
all  such  masses  as  project  and  obstruct  the  passage  of  the  incan- 
descent fluid. 

The  texture  of  the  Vesuvian  dikes  is  different  at  the  edges  and  in 
the  middle.  Towards  the  centre,  observes  M.  Necker,  the  rock  is 
larger  grained,  the  component  elements  being  in  a  far  more  crys- 
talline state ;  while  at  the  edge  the  lava  is  sometimes  vitreous,  and 
always  finer  grained.  A  thin  parting  band,  approaching  in  its 
character  to  pitchstone,  occasionally  intervenes,  at  the  contact  of 
the  vertical  dike  and  intersected  beds.  M.  Necker  mentions  one  of 
these  at  the  place  called  Primo  Monte,  in  the  Atrio  del  Cavallo ; 
and  when  I  examined  Somma,  in  1828,  I  saw  three  or  four  others 
in  different  parts  of  the  great  escarpment.  These  phenomena  are  in 
perfect  harmony  with  the  results  of  the  experiments  of  Sir  James 
Hall  and  Mr.  Gregory  Watt,  which  have  shown  that  a  glassy 
texture  is  the  effect  of  sudden  cooling,  while,  on  the  contrary,  a 
crystalline  grain  is  produced  where  fused  minerals  are  allowed  to 
consolidate  slowly  and  tranquilly  under  high  pressure. 

It  is  evident  that  the  central  portion  of  the  lava  in  a  fissure 
would,  during  consolidation,  part  with  its  heat  more  slowly  than  the 
sides,  although  the  contrast  of  circumstances  would  not  be  so  great 
as  when  we  compare  the  lava  near  the  bottom  and  at  the  surface  of 
a  current  flowing  in  the  open  air.  In  this  case  the  uppermost  part, 
where  it  has  been  in  contact  with  the  atmosphere,  and  where  re- 
frigeration has  been  most  rapid,  is  always  found  to  consist  of 
scoriform,  vitreous,  and  porous  lava ;  while  at  a  greater  depth  the 
mass  assumes  a  more  lithoidal  structure,  and  then  becomes  more  and 
more  stony  as  we  descend,  until  at  length  we  are  able  to  recognize 
with  a  magnifying  glass  the  simple  minerals  of  which  the  rock  is 
composed.  On  penetrating  still  deeper,  we  can  detect  the  con- 
stituent parts  by  the  naked  eye,  and  in  the  Vesuvian  currents 
distinct  crystals  of  augite  and  leucite  become  apparent. 

The  same  phenomenon,  observes  M.  Necker,  may  readily  be  ex- 
hibited on  a  smaller  scale,  if  we  detach  a  piece  of  liquid  lava  from 
a  moving  current.  The  fragment  cools  instantly,  and  we  find  the 
surface  covered  with  a  vitreous  coat;  while  the  interior,  although 
extremely  fine-grained,  has  a  more  stony  appearance. 

It  must,  however,  be  observed,  that  although  the  lateral  portions 
of  the  dikes  are  finer  grained  than  the  central,  yet  the  vitreous 
parting  layer  before  alluded  to  is  rare  in  Vesuvius.  This  may, 
perhaps,  be  accounted  for,  as  the  above-mentioned  author  suggests, 
by  the  great  heat  which  the  walls  of  a  fissure  may  acquire  before 
the  fluid  mass  begins  to  consolidate,  in  which  case  the  lava,  even  at 
the  sides,  would  cool  very  slowly.  Some  fissures,  also,  may  be  filled 
from  above,  as  frequently  happens  in  the  volcanos  of  the  Sandwich 
Islands,  according  to  the  observations  of  Mr.  Dana ;  and  in  this  case 
the  refrigeration  at  the  sides  would  be  more  rapid  than  when  the 


Ck.  XXX.]        NEWER   PLIOCENE   VOLCANIC   ROCKS. 


533 


melted  matter  flowed  upwards  from  the  volcanic  foci,  in  an  intensely 
heated  state.  Mr.  Darwin  informs  me  that  in  St.  Helena  almost 
every  dike  has  a  vitreous  selvage. 

The  rock  composing  the  dikes  both  in  the  modern  and  ancient 
part  of  Vesuvius  is  far  more  compact  than  that  of  ordinary  lava,  for 
the  pressure  of  a  column  of  melted  matter  in  a  fissure  greatly 
exceeds  that  in  an  ordinary  stream  of  lava  ;  and  pressure  checks  the 
expansion  of  those  gases  which  give  rise  to  vesicles  in  lava. 

There  is  a  tendency  in  almost  all  the  Yesuvian  dikes  to  divide 
into  horizontal  prisms,  a  phenomenon  in  accordance  with  the  form- 
ation of  vertical  columns  in  horizontal  beds  of  lava;  for  in  both 
eases  the  divisions  which  give  rise  to  the  prismatic  structure  are  at 
right  angles  to  the  cooling  surfaces. 

Newer  Pliocene  Period  —  Val  di  Noto.  —  I  have  already  alluded 
(see  p.  157.)  to  the  igneous  rocks  which  are  associated  with  a  great 
marine  formation  of  limestone,  sand,  and  marl  in  the  southern  part 
of  Sicily,  as  at  Vizzini  and  other  places.  In  this  formation,  which 
was  shown  to  belong  to  the  Newer  Pliocene  period,  large  beds  of 
oysters  and  corals  repose  upon  lava,  and  are  unaltered  at  the  point 
of  contact.  In  other  places  we  find  dikes  of  igneous  rock  inter- 
secting the  fossiliferous  beds,  and  converting  the  clays  into  siliceous 
schist,  the  laminae  being  contorted  and  shivered  into  innumerable 
fragments  at  the  junction,  as  near  the  town  of  Vizzini. 

The  volcanic  formations  of  the  Val  di  Noto  usually  consist  of  the 
most  ordinary  variety  of  basalt,  with  or  without  olivine.  The  rock 
is  sometimes  compact,  often  very  vesicular.  The  vesicles  are  occa- 
sionally empty,  both  in  dikes  and  currents,  and  are  in  some  localities 
filled  with  calcareous  spar,  arragonite,  and  zeolites.  The  structure 
is,  in  some  places,  spheroidal ;  in  others,  though  rarely,  columnar. 
I  found  dikes  of  amygdaloid,  wacke,  and  prismatic  basalt,  inter- 
secting the  limestone  at  the  bottom  of  the  hollow  called  Gozzo  degli 
Martiri,  below  Melilli. 

Dikes.  —  Dikes  of  vesicular  and  amygdaloidal  lava  are  also  seen 


Fig.  664. 


Fig.  665. 


;•<> 


Ground-plan  of  dikes  near  Palagonia. 

a.  Lava. 

b.  Peperino,  consisting  of  volcanic  sand,  mixed  with 

fragments  of  lava  and  limestone. 

traversing  marine  tuff  or  peperino,  west  of  Palagonia,  some  of  the 
pores  of  the  lava  being  empty,  while  others  are  filled  with  carbonate 

M  M   3 


534  DIKES   OF   LAVA.  [Cn.  XXX. 

of  lime.  In  such  cases  we  may  suppose  the  peperino  to  have  re- 
sulted from  showers  of  volcanic  sand  and  scoriae,  together  with 
fragments  of  limestone,  thrown  out  by  a  submarine  explosion, 
similar  to  that  which  gave  rise  to  Graham  Island  in  1831.  When 
the  mass  was,  to  a  certain  degree,  consolidated,  it  may  have  been 
rent  open,  so  that  the  lava  ascended  through  fissures,  the  walls  of 
which  were  perfectly  even  and  parallel.  After  the  melted  matter 
that  filled  the  rent  in  fig.  664.  had  cooled  down,  it  must  have  been 
fractured  and  shifted  horizontally  by  a  lateral  movement. 

In  the  second  figure  (fig.  665.),  the  lava  has  more  the  appearance 
of  a  vein  which  forced  its  way  through  the  peperino.  It  is  highly 
probable  that  similar  appearances  would  be  seen,  if  we  could 
examine  the  floor  of  the  sea  in  that  part  of  the  Mediterranean 
where  the  waves  have  recently  washed  away  the  new  volcanic 
island ;  for  when  a  superincumbent  mass  of  ejected  fragments  has 
been  removed  by  denudation,  we  may  expect  to  see  sections  of  dikes 
traversing  tuff,  or,  in  other  words,  sections  of  the  channels  of  com- 
munication by  which  the  subterranean  lavas  reached  the  surface.  « 


CnVXXXI.]  PLIOCENE   VOLCANOS.  535 


CHAPTER  XXXI. 

ON   THE   DIFFERENT   AGES   OF   THE   VOLCANIC   ROCKS  —  continued. 

Volcanic  rocks  of  the  Older  Pliocene  period — Tuscany — Rome — Volcanic  re- 
gion of  Olot  in  Catalonia — Cones  and  lava-currents — Ravines  and  ancient 
gravel-beds  —  Jets  of  air  called  Bufadors — Age  of  the  Catalonian  volcanos — 
Miocene  period — Brown-coal  of  the  Eifel  and  contemporaneous  trachytic  brec- 
cias— Age  of  the  brown-coal — Peculiar  characters  of  the  volcanos  of  the  upper 
and  lower  Eifel — Lake  Craters  —  Trass — Hungarian  volcanos. 

Older  Pliocene  period  —  Italy.  —  IN  Tuscany,  as  at  Radicofani, 
Viterbo,  and  Aquapendente,  and  in  the  Campagna  di  Roma,  sub- 
marine volcanic  tuffs  are  interstratified  with  the  Older  Pliocene 
strata  of  the  Subapennine  hills  in  such  a  manner  as  to  leave  no 
doubt  that  they  were  the  products  of  eruptions  which  occurred 
when  the  shelly  marls  and  sands  of  the  Subapennine  hills  were  in 
the  course  of  deposition.  This  opinion  I  expressed  *  after  my  visit 
to  Italy  in  1828,  and  it  has  recently  (1850)  been  confirmed  by  the 
arguments  adduced  by  Sir  R.  Murchison  in  favour  of  the  submarine 
origin  of  the  earlier  volcanic  rocks  of  Italy,  f  These  rocks  are  well 
known  to  rest  conformably  on  the  Subapennine  marls,  even  as  far 
south  as  Monte  Mario  in  the  suburbs  of  Rome.  On  the  exact  age 
of  the  deposits  of  Monte  Mario  new  light  has  recently  been  thrown 
by  a  careful  study  of  their  marine  fossil  shells,  undertaken  by 
MM.  Rayneval,  Vanden  Hecke,  and  Ponza.  They  have  compared 
no  less  than  160  species  J  with  the  shells  of  the  Coralline  Crag  of 
Suffolk,  so  well  described  by  Mr.  Searles  Wood;  and  the  specific 
agreement  between  the  British  and  Italian  fossils  is  so  great,  if  we 
make  due  allowance  for  geographical  distance  and  the  difference  of 
latitude,  that  we  can  have  little  hesitation  in  referring  both  to  the 
same  period  or  to  the  Older  Pliocene  of  this  work.  It  is  highly 
probable  that,  between  the  oldest  trachytes  of  Tuscany  and  the 
newest  rocks  in  the  neighbourhood  of  Naples,  a  series  of  volcanic 
products  might  be  detected  of  every  age  from  the  Older  Pliocene  to 
the  historical  epoch. 

Catalonia.  —  Geologists  are  far  from  being  able,  as  yet,  to  assign 
to  each  of  the  volcanic  groups  scattered  over  Europe  a  precise 
chronological  place  in  the  tertiary  series  ;  but  I  shall  describe  here, 

*  See  1st  edit,  of  Principles  of  Geo-  f  Geol.  Quart.  Journ.  vol.  vi.  p.  281. 
logy,  vol.  iii.  chaps,  xiii.  and  xiv.,  1833;  j  Catalogue  des  Fossiles  de  Monte 
and  former  edits,  of  this  work,  ch.  xxxi.  Mario,  Rome,  1854. 

MM  4 


536 


PLIOCENE   VOLCANOS. 


[Ce.  XXXI. 


as  probably  referable  to  some  part  of  the  Pliocene  period,  a  district 
of  extinct  volcanos  near  Olot,  in  the  north  of  Spain,  which  is  little 
known,  and  which  I  visited  in  the  summer  of  1830. 

The  whole  extent  of  country  occupied  by  volcanic  products  in 
Catalonia  is  not  more  than  fifteen  geographical  miles  from  north  to 
south,  and  about  six  from  east  to  west.  The  vents  of  eruption 
range  entirely  within  a  narrow  band  running  north  and  south ;  and 
the  branches,  which  are  represented  as  extending  eastward  in  the 
map,  are  formed  simply  of  two  lava-streams  —  those  of  Castell  Follit 
and  Cellent. 

Fig.  666. 


Volcanic  district  of  Catalonia. 

Dr.  Maclure,  the  American  geologist,  was  the  first  who  made 
known  the  existence  of  these  volcanos*;  and,  according  to  his 
description,  the  volcanic  region  extended  over  twenty  square  leagues, 
from  Amer  to  Massanet.  I  searched  in  vain  in  the  environs  of 
Massanet  in  the  Pyrenees,  for  traces  of  a  lava-current ;  and  I  can 
say  with  confidence,  that  the  adjoining  map  gives  a  correct  view  of 
the  true  area  of  the  volcanic  action. 

Geological  structure  of  the  district.  —  The  eruptions  have  burst 
entirely  through  fossiliferous  rocks,  composed  in  great  part  of  grey 

*  Maclure,  Journ.  de  Phys.,  vol.  Ixvi.  p.  219.,  1808  ;  cited  by  Daubeny,  De- 
scription of  Volcanos,  p.  24. 


CH.  XXXI.]       VOLCANOS  OF  CATALONIA.  537 

and  greenish  sandstone  and  conglomerate,  with  some  thick  beds  of 
nummulitic  limestone.  The  conglomerate  contains  pebbles  of  quartz, 
limestone,  and  Lydian  stone.  This  system  of  rocks  is  very  exten- 
sively spread  throughout  Catalonia ;  one  of  its  members  being  a  red 
sandstone,  to  which  the  celebrated  salt-rock  of  Cardona,  usually 
considered  as  of  the  cretaceous  era,  is  subordinate. 

Near  Amer,  in  the  Valley  of  the  Ter,  on  the  southern  borders  of 
the  region  delineated  in  the  map,  primary  rocks  are  seen,  consisting 
of  gneiss,  mica-schist,  and  clay-slate.  They  run  in  a  line  nearly 
parallel  to  the  Pyrenees,  and  throw  off  the  fossiliferous  strata  from 
their  flanks,  causing  them  to  dip  to  the  north  and  north-west.  This 
dip,  which  is  towards  the  Pyrenees,  is  connected  with  a  distinct  axis 
of  elevation,  and  prevails  through  the  whole  area  described  in  the 
map,  the  inclination  of  the  beds  being  sometimes  at  an  angle  of 
between  40  and  50  degrees. 

It  is  evident  that  the  physical  geography  of  the  country  has 
undergone  no  material  change  since  the  commencement  of  the  era 
of  the  volcanic  eruptions,  except  such  as  has  resulted  from  the 
introduction  of  new  hills  of  scorise,  and  currents  of  lava  upon  the 
surface.  If  the  lavas  could  be  remelted  and  poured  out  again  from 
their  respective  craters,  they  would  descend  the  same  valleys  in 
which  they  are  now  seen,  and  re-occupy  the  spaces  which  they  at 
present  fill.  The  only  difference  in  the  external  configuration  of  the 
fresh  lavas  would  consist  in  this,  that  they  would  nowhere  be  inter- 
sected by  ravines,  or  exhibit  marks  of  erosion  by  running  water. 

Volcanic  cones  and  lavas.  —  There  are  about  fourteen  distinct 
cones  with  craters  in  this  part  of  Spain,  besides  several  points 
whence  lavas  may  have  issued ;  all  of  them  arranged  along  a  narrow 
line  running  north  and  south,  as  will  be  seen  in  the  map.  The 
greatest  number  of  perfect  cones  are  in  the  immediate  neighbour- 
hood of  Olot,  some  of  which  (Fig.  667.,  Nos.  2,  3,  and  5.)  are 
represented  in  the  annexed  woodcut ;  and  the  level  plain  on  which 
that  town  stands  has  clearly  been  produced  by  the  flowing  down  of 
many  lava-streams  from  those  hills  into  the  bottom  of  a  valley, 
probably  once  of  considerable  depth,  like  those  of  the  surrounding 
country. 

In  this  drawing  an  attempt  is  made  to  represent,  by  the  shading 
of  the  landscape,  the  different  geological  formations  of  which  the 
country  is  composed.*  The  white  line  of  mountains  (No.  1.)  in  the 
distance  is  the  Pyrenees,  which  are  to  the  north  of  the  spectator, 
and  consist  of  hypogene  and  ancient  fossiliferous  rocks.  In  front  of 
these  are  the  fossiliferous  formations  (No.  4.),  which  are  in  shade. 
Still  nearer  to  us  the  hills  2,  3,  5,  are  volcanic  cones,  and  the  rest  of 
the  ground  on  which  the  sunshine  falls  is  strewed  over  with  volcanic 
ashes  and  lava. 

The  Fluvia,  which  flows  near  the  town  of  Olot,  has  cut  to  the 
depth  of  only  40  feet  through  the  lavas  of  the  plain  before  men- 

*  This  view  is  taken  from  a  sketch  which  I  made  on  the  spot  in  1830. 


538 


PLIOCENE    VOLCANOS. 

Fig.  667. 


[Cn.  XXXI, 


View  of  the  Volcanos  around  Olot  in  Catalonia. 

tioned.  The  bed  of  the  river  is  hard  basalt ;  and  at  the  bridge  of 
Santa  Madalena  are  seen  two  distinct  lava-currents,  one  above  the 
other,  separated  by  a  horizontal  bed  of  scoriae  8  feet  thick. 

In  one  place,  to  the  south  of  Olot,  the  even  surface  of  the  plain  is 
broken  by  a  mound  of  lava,  called  the  "Bosque  de  Tosca,"  the 
upper  part  of  which  is  scoriaceous,  and  covered  with  enormous 
heaps  of  fragments  of  basalt,  more  or  less  porous.  Between  the 
numerous  hummocks  thus  formed  are  deep  cavities,  having  the 
appearance  of  small  craters.  The  whole  precisely  resembles  some  of 
the  modern  currents  of  Etna,  or  that  of  Come,  near  Clermont ;  the 
last  of  which,  like  the  Bosque  de  Tosca,  supports  only  a  scanty 
vegetation. 

Most  of  the  Catalonian  volcanos  are  as  entire  as  those  in  the 
neighbourhood  of  Naples  or  on  the  flanks  of  Etna.  One  of  these, 
called  Montsacopa  (No.  3.  fig.  667.),  is  of  a  very  regular  form,  and 
has  a  circular  depression  or  crater  at  the  summit.  It  is  chiefly 
made  up  of  red  scoriae,  undistinguishable  from  those  of  the  minor 
cones  of  Etna.  The  neighbouring  hills  of  Olivet  (No.  2.)  and 
Garrinada  (No.  5.)  are  of  similar  composition  and  shape.  The 
largest  crater  of  the  whole  district  occurs  farther  to  the  east  of 
Olot,  and  is  called  Santa  Margarita.  It  is  455  feet  deep,  and  about 
a  mile  in  circumference.  Like  Astroni,  near  Naples,  it  is  richly 
covered  with  wood,  wherein  game  of  various  kinds  abounds. 

Although  the  volcanos  of  Catalonia  have  broken  out  through 
sandstone,  shale,  and  limestone,  as  have  those  of  the  Eifel,  in  Ger- 
many, to  be  described  in  the  sequel,  there  is  a  remarkable  difference 
in  the  nature  of  the  ejections  composing  the  cones  in  these  two 
regions.  In  the  Eifel,  the  quantity  of  pieces  of  sandstone  and  shale 


CH.  XXXI.] 


VOLCANOS  OF  CATALONIA. 


539 


Fig.  668. 


rt.  Conglomerate. 

b.  Thin  seams  of  volcanic  sand  and  scoriae. 


thrown  out  from  the  vents  is  often  so  immense  as  far  to  exceed  in 
volume  the  scorise,  pumice,  and  lava ;  but  I  sought  in  vain  in  the 
cones  near  Olot  for  a  single  fragment  of  any  extraneous  rock ;  and 
Don  Francisco  Bolos,  an  eminent  botanist  of  Olot,  informed  me  that 
he  had  never  .been  able  to  detect  any. 

Volcanic  sand  and  ashes  are  not  confined  to  the  cones,  but  have 
been  sometimes  scattered  by  the  wind  over  the  country,  and  drifted 

into  narrow  valleys,  as  is  seen 
between  Olot  and  Cellent,  where 
the  annexed  section  (fig.  668.)  is 
exposed.  The  light  cindery  vol- 
canic matter  rests  in  thin  re- 
gular layers,  just  as  it  alighted 
on  the  slope  formed  of  the  solid 
conglomerate.  No  flood  could 
have  passed  through  the  valley 
since  the  scorise  fell,  or  these  would  have  been  for  the  most  part 
removed.  The  currents  of  lava  in  Catalonia,  like  those  of  Auvergne, 
the  Yivarais,  Iceland,  and  all  mountainous  countries,  are  of  con- 
siderable depth  in  narrow  defiles,  but  spread  out  into  comparatively 
thin  sheets  in  places  where  the  valleys  widen.  If  a  river  has  flowed 
on  nearly  level  ground,  as  in  the  great  plain  near  Olot,  the  water 
has  only  excavated  a  channel  of  slight  depth;  but  where  the  de- 
clivity is  great,  the  stream  has  cut  a  deep  section,  sometimes  by 
penetrating  directly  through  the  central  part  of  a  lava-current,  but 
more  frequently  by  passing  between  the  lava  and  the  secondary  or 
tertiary  rock  which  bounds  the  valley.  Thus,  in  the  accompanying 
section  (fig.  669.),  at  the  bridge  of  Cellent,  six  miles  east  of  Olot,  we 
see  the  lava  on  one  side  of  the  small  stream ;  while  the  inclined 
stratified  rocks  constitute  the  channel  and  opposite  bank.  The 

Fig.  669. 


Section  above  the  bridge  of  Cellent 


a.  Scoriaceous  lava. 

b.  Schistose  basalt. 

c.  Columnar  basalt. 


(I.  Scoriae,  vegetable  soil,  and  alluvium. 
e.  Nummulitic  limestone. 
/.  Micaceous  grey  sandstone. 


upper  part  of  the  lava  at  that  place,  as  is  usual  in  the  currents  of 
Etna  and  Vesuvius,  is  scoriaceous ;  farther  down  it  becomes  less 


540  PLIOCENE    VOLCANOS.  [Cn.  XXXI. 

porous,  and  assumes  a  spheroidal  structure ;  still  lower  it  divides  in 
horizontal  plates,  each  about  2  inches  in  thickness,  and  is  more 
compact.  Lastly,  at  the  bottom  is  a  mass  of  prismatic  basalt  about 
5  feet  thick.  The  vertical  columns  often  rest  immediately  on  the 
subjacent  stratified  rocks ;  but  there  is  sometimes  an  intervention  of 
sand  and  scoriae  such  as  cover  the  country  during  volcanic  eruptions, 
and  which,  unless  protected,  as  here,  by  superincumbent  lava,  is 
washed  away  from  the  surface  of  the  land.  Sometimes,  the  bed  d 
contains  a  few  pebbles  and  angular  fragments  of  rock ;  in  other 
places  fine  earth,  which  may  have  constituted  an  ancient  vegetable 
soil. 

In  several  localities,  beds  of  sand  and  ashes  are  interposed  between 
the  lava  and  subjacent  stratified  rock,  as  may  be  seen  if  we  follow 
the  course  of  the  lava-current  which  descends  from  Las  Planas 
towards  Amer,  and  stops  two  miles  short  of  that  town.  The  river 
there  has  often  cut  through  the  lava,  and  through  18  feet  of  under- 
lying limestone.  Occasionally  an  alluvium,  several  feet  thick,  is 
interposed  between  the  igneous  and  marine  formations ;  and  it  is 
interesting  to  remark  that  in  this,  as  in  other  beds  of  pebbles 
occupying  a  similar  position,  there  are  no  rounded  fragments  of 
lava ;  whereas  in  the  most  modern  gravel-beds  of  the  rivers  of  this 
country  volcanic  pebbles  are  abundant. 

The  deepest  excavation  made  by  a  river  through  lava,  which  I 
observed  in  this  part  of  Spain,  is  seen  in  the  bottom  of  a  valley  near 
San  Feliu  de  Pallerols,  opposite  the  Castell  de  Stolles.  The  lava 
there  has  filled  up  the  bottom  of  a  valley,  and  a  narrow  ravine  has 
been  cut  through  it  to  the  depth  of  100  feet.  In  the  lower  part  the 
lava  has  a  columnar  structure.  A  great  number  of  ages  were  pro- 
bably required  for  the  erosion  of  so  deep  a  ravine ;  but  we  have  no 
reason  to  infer  that  this  current  is  of  higher  antiquity  than  those 
of  the  plain  near  Olot.  The  fall  of  the  ground,  and  consequent 
velocity  of  the  stream,  being  in  this  case  greater,  a  more  considerable 
volume  of  rock  may  have  been  removed  in  the  same  time. 

I  shall  describe  one  more  section  (fig.  670.)  to  elucidate  the  phe- 
nomena of  this  district.  A  lava-stream,  flowing  from  a  ridge  of 
hills  on  the  east  of  Olot,  descends  a  considerable  slope,  until  it 
reaches  the  valley  of  the  river  Fluvia.  Here,  for  the  first  time,  it 
comes  in  contact  with  running  water,  which  has  removed  a  portion, 
and  laid  open  its  internal  structure  in  a  precipice  about  130  feet  in 
height,  at  the  edge  of  which  stands  the  town  of  Castell  Follit. 

By  the  junction  of  the  rivers  Fluvia  and  Teronel,  the  mass  of  lava 
has  been  cut  away  on  two  sides ;  and  the  insular  rock  B  (fig.  670.) 
has  been  left,  which  was  probably  never  so  high  as  the  cliff  A,  as  it 
may  have  constituted  the  lower  part  of  the  sloping  side  of  the 
original  current. 

From  an  examination  of  the  vertical  cliffs,  it  appears  that  the 
upper  part  of  the  lava  on  which  the  town  is  built  is  scoriaceous, 
passing  downwards  into  a  spheroidal  basalt;  some  of  the  huge 
spheroids  being  no  less  than  6  feet  in  diameter.  Below  this  is  a 


CH.  XXXI.]      yOLCAXOS  OF  CATALONIA. 

Fig.  670. 


Rirer  Fluvia, 


Section  at  Castell  Follit. 

A.  Church  and  town  of  Castell  Follit,  overlooking  precipices  of  basalt. 

B.  Small  island,  on  each  side  of  which  branches  of  the  river  Teronel  flow  to  meet  the 

Fluvia. 

c.  Precipice  of  basaltic  lava,  chiefly  columnar,  about  130  feet  in  height. 

d.  Ancient  alluvium,  underlying  the  lava-current. 

e.  Inclined  strata  of  sandstone. 

more  compact  basalt,  with  crystals  of  olivine.  There  are  in  all  five 
distinct  ranges  of  basalt,  the  uppermost  spheroidal,  and  the  rest 
prismatic,  separated  by  thinner  beds  not  columnar,  and  some  of 
which  are  schistose.  These  were  probably  formed  by  successive 
flows  of  lava,  whether  during  the  same  eruption  or  at  different 
periods.  The  whole  mass  rests  on  alluvium,  ten  or  twelve  feet  in 
thickness,  composed  of  pebbles  of  limestone  and  quartz,  but  without 
any  intermixture  of  igneous  rocks  ;  in  which  circumstance  alone  it 
appears  to  differ  from  the  modern  gravel  of  the  Fluvia. 

Bufadors.  —  The  volcanic  rocks  near  Olot  have  often  a  cavernous 
structure,  like  some  of  the  lavas  of  Etna ;  and  in  many  parts  of  the 
hill  of  Batet,  in  the  environs  of  the  town,  the  sound  returned  by  the 
earth,  when  struck,  is  like  that  of  an  archway.  At  the  base  of  the 
same  hill  are  the  mouths  of  several  subterranean  caverns,  about 
twelve  in  number,  called  in  the  country  "  bufadors ; "  from  which  a 
current  of  cold  air  issues  during  summer,  but  in  winter  it  is  said  to 
be  scarcely  perceptible.  I  visited  one  of  these  bufadors  in  the 
beginning  of  August,  1830,  when  the  heat  of  the  season  was  un- 
usually intense,  and  found  a  cold  wind  blowing  from  it,  which  may 
easily  be  explained ;  for  as  the  external  air,  when  rarefied  by  heat, 
ascends,  the  pressure  of  the  colder  and  heavier  air  of  the  caverns 
in  the  interior  of  the  mountain  causes  it  to  rush  out  to  supply  its 
place. 

In  regard  to  the  age  of  these  Spanish  volcanos,  attempts  have 
been  made  to  prove,  that  in  this  country,  as  well  as  in  Auvergne 
and  the  Eifel,  the  earliest  inhabitants  were  eye-witnesses  to  the 
volcanic  action.  In  the  year  1421,  it  is  said,  when  Olot  was  de- 
stroyed by  an  earthquake,  an  eruption  broke  out  near  Amer,  and 
consumed  the  town.  The  researches  of  Don  Francisco  Bolos  have, 
I  think,  shown,  in  the  most  satisfactory  manner,  that  there  is  no 
good  historical  foundation  for  the  latter  part  of  this  story  ;  and  any 


542 


VOLCANOS    OF    CATALONIA. 


[Ce.  XXXI. 


geologist  who  has  visited  Amer  must  be  convinced  that  there  never 
was  any  eruption  on  that  spot.  It  is  true  that,  in  the  year  above 
mentioned,  the  whole  of  Olot,  with  the  exception  of  a  single  house, 
was  cast  down  by  an  earthquake ;  one  of  those  shocks  which,  at 
distant  intervals  during  the  last  five  centuries,  have  shaken  the 
Pyrenees,  and  particularly  the  country  between  Perpignan  and  Olot, 
where  the  movements,  at  the  period  alluded  to,  were  most  violent. 

The  annihilation  of  the  town  may,  perhaps,  have  been  due  to  the 
cavernous  nature  of  the  subjacent  rocks  ;  for  Catalonia  is  beyond 
the  line  of  those  European  earthquakes  which  have,  within  the 
period  of  history,  destroyed  towns  throughout  extensive  areas. 

As  we  have  no  historical  records,  then,  to  guide  us  in  regard  to 
the  extinct  volcanos,  we  must  appeal  to  geological  monuments.  The 
annexed  diagram  (fig.  671.)  will  present  to  the  reader,  in  a  synop- 
tical form,  the  results  obtained  from  numerous  sections. 

Fig.  671. 


Superposition  of  rocks  in  the  volcanic  district  of  Catalonia. 

a.  Sandstone  and  nummulitic  limestone. 

b.  Older  alluvium  without  volcanic  pebbles. 


c.  Cones  of  scoriae  and  lava. 


d.  Newer  alluvium. 


The  more  modern  alluvium  (c?)  is  partial,  and  has  been  formed  by 
the  action  of  rivers  and  floods  upon  the  lava;  whereas  the  older 
gravel  (#)  was  strewed  over  the  country  before  the  volcanic  erup- 
tions. In  neither  have  any  organic  remains  been  discovered;  so 
that  we  can  merely  affirm  as  yet,  that  the  volcanos  broke  out  after 
the  elevation  of  some  of  the  newest  rocks  of  the  mummulitic 
(Eocene)  series  of  Catalonia,  and  before  the  formation  of  an  allu- 
vium (d)  of  unknown  date.  The  integrity  of  the  cones  merely 
shows  that  the  country  has  not  been  agitated  by  violent  earthquakes, 
or  subjected  to  the  action  of  any  great  flood  since  their  origin. 

East  of  Olot,  on  the  Catalonian  coast,  marine  tertiary  strata 
occur,  which,  near  Barcelona,  attain  the  height  of  about  500  feet. 
From  the  shells  which  I  collected,  these  strata  appear  to  correspond 
in  age  with  the  Subapennine  beds ;  and  it  is  not  improbable  that 
their  upheaval  from  beneath  the  sea  took  place  during  the  period  of 
volcanic  eruption  round  Olot.  In  that  case  these  eruptions  may 
have  occurred  at  the  close  of  the  Older  Pliocene  era,  but  perhaps 
subsequently,  for  their  age  is  at  present  quite  uncertain. 

Volcanic  rocks  of  the  Eifel.  —  The  chronological  relations  of  the 
volcanic  rocks  of  the  Lower  Rhine  and  the  Eifel  are  also  involved 
in  a  considerable  degree  of  ambiguity ;  but  we  know  that  some  por- 
tion of  them  were  coeval  with  certain  tertiary  deposits  called 


Cfi.  XXXI.]  TERTIARY  VOLCANIC    ROCKS.  543 

"  Brown-Coal "  by  the  Germans,  which  probably  belong  in  part  to 
the  Miocene,  and  in  part  to  the  Upper  Eocene,  epoch. 

This  Brown-Coal  is  seen  on  both  sides  of  the  Rhine,  in  the  neigh- 
bourhood of  Bonn,  resting  unconformably  on  highly  inclined  and 
vertical  strata  of  Silurian  and  Devonian  rocks.  Its  geographical 
position,  and  the  space  occupied  by  the  volcanic  rocks,  both  of  the 
Westerwald  and  Eifel,  will  be  seen  by  referring  to  the  map 
(fig.  672.),  for  which  I  am  indebted  to  Mr.  Horner,  whose  residence 
for  some  years  in  the  country  enabled  him  to  verify  the  maps  of 
MM.  Noeggerath  and  Yon  Oeynhausen,  from  which  that  now  given 
has  been  principally  compiled.* 

Fig.  672. 


Map  of  the  volcanic  region  of  the  Upper  and  Lower  Eifel. 
12345  English  Miles. 


K>;:;:;.\1  Volcanic     f  A.  of  the  Upper  Eifel. 
li-'----'l  District.     I  B.  of  the  Lower  Eifel. 

Trachyte. 


Points  of  eruption,   with   craters  and 
scoriae. 

Basalt 
Brown-coal. 


N.  B.  The  country  in  that  part  of  the  map  which  is  left  blank  is  composed  of  inclined  Silurian 
and  Devonian  rocks. 

The  Brown-Coal  formation  of  that  region  consists  of  beds  of  loose 
sand,  sandstone,  and  conglomerate,  clay  with  nodules  of  clay-iron- 
stone, and  occasionally  silex.  Layers  of  light  brown,  and  sometimes 
black  lignite  are  interstratified  with  the  clays  and  sands,  and  often 


*  Horner,  Trans,  of  Geol.  Soc.  2d  ser.  vol.  v. 


544  AGE    OF    THE    BROWN-COAL.  [Cu.  XXXI. 

irregularly  diffused  through  them.  They  contain  numerous  impres- 
sions of  leaves  and  stems  of  trees,  and  are  extensively  worked  for 
fuel,  whence  the  name  of  the  formation. 

In  several  places,  layers  of  trachytic  tuff  are  interstratified,  and  in 
these  tuffs  are  leaves  of  plants  identical  with  those  found  in  the 
brown-coal,  showing  that,  during  the  period  of  the  accumulation  of 
the  latter,  some  volcanic  products  were  ejected. 

Mr.  Von  Decken  in  his  work  on  the  Siebengebirge  *,  has  given  a 
copious  list  of  the  animal  and  vegetable  remains  of  the  freshwater 
strata  associated  with  the  brown-coal.  Plants  of  the  genera  Flabel- 
laria,  Ceanothus,  and  Daphnogene,  including  D.  cinnamomifolia 
(fig.  169.  p.  192.)  occur  in  these  beds,  with  nearly  150  other  plants, 
if  we  include  all  which  have  been  named  from  the  somewhat  uncer- 
tain data  furnished  by  leaves.  They  are  referred  for  the  most  part 
to  living  genera,  but  to  extinct  species.  Among  the  animal  remains, 
both  vertebrate  and  invertebrate,  many  are  peculiar,  while  some  few, 
such  as  Littorinella  acuta,  Desh.,  help  to  approximate  these  strata 
with  some  of  the  upper  freshwater  portions  of  the  Mayence  basin. 
The  marine  base  of  the  Mayence  series  consists  of  sandy  strata 
closely  allied  in  geological  date,  as  we  have  already  seen,  p.  191.,  to 
the  Limburg  group,  called  Upper  Eocene  in  this  work.  But  in  re- 
gard to  the  Rhenish  freshwater  deposits  near  Bonn,  so  large  a  pro- 
portion of  the  plants,  insects,  fish,  batrachians,  and  other  fossils  are 
such  as  have  been  met  with  nowhere  else,  that  we  cannot  as  yet 
assign  to  them  a  very  definite  place  in  the  chronological  series. 
They  were  undoubtedly  formed  during  that  long  interval  of  time 
which  separated  the  Nummulitic  from  the  Falunian  tertiary  formations, 
so  that  they  are  newer  than  the  Middle  Eocene,  and  older  than  the 
Miocene  strata  of  our  Table  given  at  page  105.  The  classification 
of  the  deposits  belonging  to  this  interval  must  still  be  regarded  as 
debatable  ground,  very  different  opinions  being  entertained  on  the 
subject  by  geologists  of  high  authority.  Should  a  passage  be  even- 
tually made  out  from  the  tertiaries  of  the  north  of  Germany,  on 
which  the  labours  of  M.  Beyrich  have  thrown  so  much  light,  to  the 
faluns  of  the  Loire,  by  the  discovery  of  beds  intermediate  in  age  and 
paleontological  characters,  the  best  line  of  demarcation  that  we  can 
adopt  is  that  proposed  by  M.  Hebert,  according  to  which  all  the 
Limburg  beds,  the  Gres  de  Fontainebleau,  the  lower  part  of  the 
Mayence  basin,  and  the  Hempstead  beds  of  the  Isle  of  Wight  (see 
p.  193.)  are  classed  as  Lower  Miocene,  while  the  Faluns  rank  as 
Upper  Miocene.  Between  these  formations  there  is  still  so  vast  an 
hiatus  that  I  have  thought  it  inexpedient,  for  reasons  before  explained, 
to  unite  them  under  a  common  name.f 

*  Geognost.  Beschreib.  des  Siebenge-  Hamilton,  Esq.,  P.  G.  S.,  has  been 

birges  am  Rhein.  Bonn,  1852.  published  (Geol.  Quart.  Journ.  vol.  x. 

f  While  this  sheet  was  passing  p.  254),  in  which  the  question  of  classi- 

through  the  press,  a  valuable  paper  fication  above  alluded  to  is  discussed, 

on  the  Brown-Coal  and  other  deposits  Whatever  terminology  be  adopted,  I 

of  the  Mayence  Basin,  by  William  J.  would  strongly  urge  the  necessity  of 


CHT  XXXI.]  TERTIARY   VOLCANIC    ROCKS.  545 

The  fishes  of  the  brown-coal  near  Bonn  are  found  in  a  bituminous 
shale,  called  paper-coal,  from  being  divisible  into  extremely  thin 
leaves.  The  individuals  are  very  numerous  ;  but  they  appear  to 
belong  to  a  small  number  of  species,  some  of  which  were  referred  by 
Agassiz  to  the  genera  Leuciscus,  Aspius,  and  Perca.  The  remains  of 
frogs  also,  of  extinct  species,  have  been  discovered  in  the  paper- coal ; 
and  a  complete  series  may  be  seen  in  the  museum  at  Bonn,  from  the 
most  imperfect  state  of  the  tadpole  to  that  of  the  full-grown  animal. 
With  these  a  salamander,  scarcely  distinguishable  from  the  recent 
species,  has  been  found,  and  the  remains  of  many  insects. 

A  vast  deposit  of  gravel,  chiefly  composed  of  pebbles  of  white 
quartz,  but  containing  also  a  few  fragments  of  other  rocks,  lies  over 
the  brown-coal,  forming  sometimes  only  a  thin  covering,  at  others 
attaining  a  thickness  of  more  than  100  feet.  This  gravel  is  very 
distinct  in  character  from  that  now  forming  the  bed  of  the  Rhine. 
It  is  called  "  Kiesel  gerolle "  by  the  Germans,  often  reaches  great 
elevations,  and  is  covered  in  several  places  with  volcanic  ejections. 
It  is  evident  that  the  country  has  undergone  great  changes  in  its 
physical  geography  since  this  gravel  was  formed ;  for  its  position 
has  scarcely  any  relation  to  the  existing  drainage,  and  the  great 
valley  of  the  Rhine  and  all  the  more  modern  volcanic,  rocks  of  the 
same  region  are  posterior  to  it  in  date. 

Some  of  the  newest  beds  of  volcanic  sand,  pumice,  and  scoriag  are 
interstratified  near  Andernach  and  elsewhere  with  the  loam  called 
loess,  which  was  before  described  as  being  full  of  land  and  freshwater 
shells  of  recent  species,  and  referable  to  the  Post-Pliocene  period.  I 
have  before  hinted  (see  p.  124.)  that  this  intercalation  of  volcanic 
matter  between  beds  of  loess  may  possibly  be  explained  without 
supposing  the  last  eruptions  of  the  Lower  Eifel  to  have  taken  place 
so  recently  as  the  era  of  the  deposition  of  the  loess. 

The  igneous  rocks  of  the  Westerwald,  and  of  the  mountains  called 
the  Siebengebirge,  consist  partly  of  basaltic  and  partly  of  trachytic 
lavas,  the  -latter  being  in  general  the  more  ancient  of  the  two.  There 
are  many  varieties  of  trachyte,  some  of  which  are  highly  crystalline, 
resembling  a  coarse-grained  granite,  with  large  separate  crystals  of 
felspar.  Trachytic  tuff  is  also  very  abundant.  These  formations, 
some  of  which  were  certainly  contemporaneous  with  tne  origin  of 
the  brown-coal,  were  the  first  of  a  long  series  of  eruptions,  the 
more  recent  of  which  happened  when  the  country  had  acquired 
nearly  all  its  present  geographical  features. 

Newer  volcanes  of  the  Eifel.  —  Lake-craters.  —  As  I  recognized 
in  the  more  modern  volcanos  of  the  Eifel  characters  distinct  from 
any  previously  observed  by  me  in  those  of  France,  Italy,  or  Spain,  I 
shall  briefly  describe  them.  The  fundamental  rocks  of  the  district 
are  grey  and  red  sandstones  and  shales,  with  some  associated  lime- 
stones, replete  with  fossils  of  the  Devonian  or  Old  Red  Sandstone 

referring  the  Hempstead  beds  of  the      be   named  Lower  Miocene  or  Upper 
Isle  of  Wight  and  the  Limburg  strata      Eocene, 
to  one  and  the  same  period,  whether  it 

NN 


546 


TERTIARY  VOLCANIC  ROCKS. 


[Cn.  XXXI. 


group.  The  volcanos  broke  out  in  the  midst  of  these  inclined  strata, 
and  when  the  present  systems  of  hills  and  valleys  had  already  been 
formed.  The  eruptions  occurred  sometimes  at  the  bottom  of  deep 
valleys,  sometimes  on  the  summit  of  hills,  and  frequently  on  inter- 
vening platforms.  In  travelling  through  this  district  we  often  fall 
upon  them  most  unexpectedly,  and  may  find  ourselves  on  the  very 
edge  of  a  crater  before  we  had  been  led  to  suspect  that  we  were 
approaching  the  site  of  any  igneous  outburst.  Thus,  for  example, 
on  arriving  at  the  village  of  Gemund,  immediately  south  of  Daun, 
we  leave  the  stream,  which  flows  at  the  bottom  of  a  deep  valley  in 
which  strata  of  sandstone  and  shale  crop  out.  We  then  climb  a  steep 
hill,  on  the  surface  of  which  we  see  the  edges  of  the  same  strata 
dipping  inwards  towards  the  mountain.  When  we  have  ascended  to 
a  considerable  height,  we  see  fragments  of  scoriae  sparingly  scattered 
over  the  surface;  until,  at  length,  on  reaching  the  summit,  we  find 
ourselves  suddenly  on  the  edge  of  a  tarn,  or  deep  circular  lake-basin 
(see  fig.  673.). 

Fig.  673. 


The  Gemunder  Maar. 
Fig.  674. 


a.  Village  of  Gemund. 
6.  Gemunder  Maar. 


c.  WefnfelderTtfaar. 

d.  Schalkenmehren  Maar. 


This,  which  is  called  the  Gemunder  Maar,  is  one  of  three  lakes 
which  are  in  immediate  contact,  the  same  ridge  forming  the  barrier 
of  two  neighbouring  cavities.  On  viewing  the  first  of  these  (fig.  673 .), 
we  recognize  the  ordinary  form  of  a  crater,  for  which  we  have  been 
prepared  by  the  occurrence  of  scoriae  scattered  over  the  surface  of 
the  soil.  But  on  examining  the  walls  of  the  crater  we  find  precipices 
of  sandstone  and  shale  which  exhibit  no  signs  of  the  action  of  heat ; 
and  we  look  in  vain  for  those  beds  of  lava  and  scoriae,  dipping  in 
opposite  directions  on  every  side,  which  we  have  been  accustomed  to 
consider  as  characteristic  of  volcanic  vents.  As  we  proceed,  however, 
to  the  opposite  side  of  the  lake,  and  afterwards  visit  the  craters  c 
and  d  (fig.  674.),  we  find  a  considerable  quantity  of  scoriae  and  some 


Cn.'XXXI.J  LAKE-CRATERS   OF    THE   EIFEL.  547 

lava,  and  see  the  whole  surface  of  the  soil  sparkling  with  volcanic 
sand,  and  strewed  with  ejected  fragments  of  half-fused  shale,  which 
preserves  its  laminated  texture  in  the  interior,  while  it  has  a  vitrified 
or  scoriform  coating. 

A  few  miles  to  the  south  of  the  lakes  above  mentioned  occurs  the 
Pulvermaar  of  Gillenfeld,  an  oval  lake  of  very  regular  form,  and 
surrounded  by  an  unbroken  ridge  of  fragmentary  materials,  consisting 
of  ejected  shale  and  sandstone,  and  preserving  a  uniform  height  of 
about  150  feet  above  the  water.  The  side  slope  in  the  interior  is 
at  an  angle  of  about  45  degrees;  on  the  exterior,  of  35  degrees. 
Volcanic  substances  are  intermixed  very  sparingly  with  the  ejections, 
which  in  this  place  entirely  conceal  from  view  the  stratified  rocks  of 
the  country.* 

The  Meerfelder  Maar  is  a  cavity  of  far  greater  size  and  depth, 
hollowed  out  of  similar  strata;  the  sides  presenting  some  abrupt 
sections  of  inclined  secondary  rocks,  which  in  other  places  are  buried 
under  vast  heaps  of  pulverized  shale.  I  could  discover  no  scorias 
amongst  the  ejected  materials,  but  balls  of  olivine  and  other  volcanic 
substances  are  mentioned  as  having  been  found. "j"  This  cavity,  which 
we  must  suppose  to  have  discharged  an  immense  volume  of  gas,  is 
nearly  a  mile  in  diameter,  and  is  said  to  be  more  than  one  hundred 
fathoms  deep.  In  the  neighbourhood  is  a  mountain  called  the  Mosen- 
berg,  which  consists  of  red  sandstone  and  shale  in  its  lower  parts, 
but  supports  on  its  summit  a  triple  volcanic  cone,  while  a  distinct 
current  of  lava  is  seen  descending  the  flanks  of  the  mountain.  The 
edge  of  the  crater  of  the  largest  cone  reminded  me  much  of  the  form 
and  characters  of  that  of  Vesuvius  ;  but  I  was  much  struck  with  the 
precipitous  and  almost  overhanging  wall  or  parapet  which  the  scoriae 
presented  towards  the  exterior,  as  at  a  b  (fig.  675.);  which  I  can 
only  explain  by  supposing  that  fragments  of  red-hot  lava,  as  they  fell 
round  the  vent,  were  cemented  together  into  one  compact  mass,  in 
consequence  of  continuing  to  be  in  a  half-melted  state. 

Fig.  675. 


.  Stratified  rocks.  v.  Volcanic. 

Outline  of  the  Mosenberg,  Upper  Eifel. 

If  we  pass  from  the  Upper  to  the  Lower  Eifel,  from  A  to  B  (see 
map,  p.  543.),  we  find  the  celebrated  lake-crater  of  Laach,  which  has 
a  greater  resemblance  than  any  of  those  before  mentioned  to  the 
Lago  di  Bolsena,  and  others  in  Italy,  —  being  surrounded  by  a  ridge 

*  Scrope,  Edin.  Journ.  of  Science,  f  Hibbert,  Extinct  Volcanos  of  the 
June,  1826,  p.  145.  Rhine,  p.  24. 

NN   2 


548  TERTIARY   VOLCANIC   ROCKS.  [Cn.  XXXI. 

of  gently  sloping  hills,  composed  of  loose  tuffs,  scoriae,  and  blocks  of 
a  variety  of  lavas. 

One  of  the  most  interesting  volcanos  on  the  left  bank  of  the  Rhine 
near  Bonn  is  called  the  R-oderberg.  It  forms  a  circular  crater  nearly 
a  quarter  of  a  mile  in  diameter,  and  100  feet  deep,  now  covered  with 
fields  of  corn.  The  highly  inclined  strata  of  ancient  sandstone  and 
shale  rise  even  to  the  rim  of  one  side  of  the  crater ;  but  they  are 
overspread  by  quartzose  gravel,  and  this  again  is  covered  by  volcanic 
scoriae  and  tufaceous  sand.  The  opposite  wall  of  the  crater  is  com- 
posed of  cinders  and  scorified  rock,  like  that  at  the  summit  of  Vesu- 
vius. It  is  quite  evident  that  the  eruption  in  this  case  burst  through 
the  sandstone  and  alluvium  which  immediately  overlies  it;  and  I 
observed  some  of  the  quartz  pebbles  mixed  with  scoriae  on  the  flanks 
of  the  mountain,  as  if  they  had  been  cast  up  into  the  air,  and  had 
fallen  again  with  the  volcanic  ashes.  I  have  already  observed,  that 
a  large  part  of  this  crater  has  been  filled  up  with  the  loess  (p.  123.). 

The  most  striking  peculiarity  of  a  great  many  of  the  craters  above 
described,  is  the  absence  of  any  signs  of  alteration  or  torrefaction  in 
their  walls,  when  these  are  composed  of  regular  strata  of  ancient 
sandstone  and  shale.  It  is  evident  that  the  summits  of  hills  formed 
of  the  above-mentioned  stratified  rocks  have,  in  some  cases,  been 
carried  away  by  gaseous  explosions,  while  at  the  same  time  no  lava, 
and  often  a  very  small  quantity  only  of  scoriae,  has  escaped  from  the 
newly  formed  cavity.  There  is,  indeed,  no  feature  in  the  Eifel  vol- 
canos more  worthy  of  note,  than  the  proofs  they  afford  of  very 
copious  aeriform  discharges,  unaccompanied  by  the  pouring  out  of 
melted  matter,  except,  here  and  there,  in  very  insignificant  volume. 
I  know  of  no  other  extinct  volcanos  where  gaseous  explosions  of  such 
magnitude  have  been  attended  by  the  emission  of  so  small  a  quantity 
of  lava.  Yet  I  looked  in  vain  in  the  Eifel  for  any  appearances 
which  could  lend  support  to  the  hypothesis,  that  the  sudden  rushing 
out  of  such  enormous  volumes  of  gas  had  ever  lifted  up  the  stratified 
rocks  immediately  around  the  vent,  so  as  to  form  conical  masses, 
having  their  strata  dipping  outwards  on  all  sides  from  a  central  axis, 
as  is  assumed  in  the  theory  of  elevation  craters,  alluded  to  in  Chap. 
XXIX. 

Trass.  —  In  the  Lower  Eifel,  eruptions  of  trachytic  lava  preceded 
the  emission  of  currents  of  basalt,  and  immense  quantities  of  pumice 
were  thrown  out  wherever  trachyte  issued.  The  tufaceous  alluvium 
called  trass,  which  has  covered  large  areas  in  this  region  and  choked 
up  some  valleys  now  partially  re-excavated,  is  unstratified.  Its  base 
consists  almost  entirely  of  pumice,  in  which  are  included  fragments 
of  basalt  and  other  lavas,  pieces  of  burnt  shale,  slate,  and  sandstone, 
and  numerous  trunks  and  branches  of  trees.  If  this  trass  was  formed 
during  the  period  of  volcanic  eruptions,  it  may  perhaps  have  origi- 
nated in  the  manner  of  the  moya  of  the  Andes. 

We  may  easily  conceive  that  a  similar  mass  might  now  be  pro- 
duced, if  a  copious  evolution  of  gases  should  occur  in  one  of  the  lake 
basins.  The  water  might  remain  for  weeks  in  a  state  of  violent 


Cn>XXXI.J  HUNGARIAN   VOLCANOS.  549 

ebullition,  until  it  became  of  the  consistency  of  mud,  just  as  the  sea 
continued  to  be  charged  with  red  mud  round  Graham's  Island,  in  the 
Mediterranean,  in  the  year  1831.  If  a  breach  should  then  be  made 
in  the  side  of  the  cone,  the  flood  would  sweep  away  great  heaps  of 
ejected  fragments  of  shale  and  sandstone,  which  would  be  borne 
down  into  the  adjoining  valleys.  Forests  might  be  torn  up  by  such 
a  flood,  and  thus  the  occurrence  of  the  numerous  trunks  of  trees  dis- 
persed irregularly  through  the  trass,  can  be  explained. 

Hungary. — M.  Beudant,  in  his  elaborate  work  on  Hungary,  de- 
scribes five  distinct  groups  of  volcanic  rocks,  which  although  no- 
where of  great  extent,  form  striking  features  in  the  physical  geo- 
graphy of  that  country,  rising  as  they  do  abruptly  from  extensive 
plains  composed  of  tertiary  strata.  They  may  have  constituted 
islands  in  the  ancient  sea,  as  Santorin  and  Milo  now  do  in  the  Gre- 
cian Archipelago ;  and  M.  Beudant  has  remarked  that  the  mineral 
products  of  the  last-mentioned  islands  resemble  remarkably  those  of 
the  Hungarian  extinct  volcanos,  where  many  of  the  same  minerals, 
as  opal,  calcedony,  resinous  silex  (silex  resinite),  pearlite,  obsidian, 
and  pitchstone  abound. 

The  Hungarian  lavas  are  chiefly  felspathic,  consisting  of  different 
varieties  of  trachyte ;  many  are  cellular,  and  used  as  millstones  ; 
some  so  porous  and  even  scoriform  as  to  resemble  those  which  have 
issued  in  the  open  air.  Pumice  occurs  in  great  quantity ;  and  there 
are  conglomerates,  or  rather  breccias,  wherein  fragments  of  trachyte 
are  bound  together  by  pumiceous  tuff,  or  sometimes  by  silex. 

It  is  probable  that  these  rocks  were  permeated  by  the  waters  of 
hot  springs,  impregnated,  like  the  Geysers,  with  silica ;  or  in  some 
instances,  perhaps,  by  aqueous  vapours,  which,  like  those  of  Lance- 
rote,  may  have  precipitated  hydrate  of  silica. 

By  the  influence  of  such  springs  or  vapours  the  trunks  and 
branches  of  trees  washed  down  during  floods,  and  buried  in  tuffs  on 
the  flanks  of  the  mountains,  are  supposed  to  have  become  silicified. 
It  is  scarcely  possible,  says  M.  Beudant,  to  dig  into  any  of  the 
pumiceous  deposits  of  these  mountains  without  meeting  with  opalized 
wood,  and  sometimes  entire  silicified  trunks  of  trees  of  great  size 
and  weight. 

It  appears  from  the  species  of  shells  collected  principally  by 
M.  Boue,  and  examined  by  M.  Deshayes,  that  the  fossil  remains  im- 
bedded in  the  volcanic  tuffs,  and  in  strata  alternating  with  them  in 
Hungary,  are  of  the  Miocene  type,  and  not  identical,  as  was  formerly 
supposed,  with  the  fossils  of  the  Paris  basin. 


NK  3 


550  TERTIARY   VOLCANIC   ROCKS.  [CH.  XXXII. 


CHAPTER  XXXH. 

ON   THE   DIFFERENT   AGES   OF    THE   VOLCANIC   ROCKS  —  continued. 

Volcanic  rocks  of  the  Pliocene,  Miocene,  and  Eocene  periods  continued — Au- 
vergne — Mont  Dor — Breccias  and  alluviums  of  Mont  Perrier,  with  bones  of 
quadrupeds — Kiver  dammed  up  by  lava-current — Range  of  minor  cones  from 
Auvergne  to  the  Vivarais — Monts  Dome — Puy  de  Come — Puy  de  Pariou — 
Cones  not  denuded  by  general  flood — Velay — Bones  of  quadrupeds  buried  in 
scorise — Cantal — Eocene  volcanic  rocks — Tuffs  near  Clermont — Hill  of  Ger- 
govia — Trap  of  Cretaceous  period  —  Oolitic  period  —  New  Red  Sandstone  pe- 
riod—  Carboniferous  period — Old  Red  Sandstone  period — "Rock  and  Spindle" 
near  St.  Andrew's  —  Silurian  period — Cambrian  volcanic  rocks. 

Volcanic  Rocks  of  Auvergne. — THE  extinct  volcanos  of  Auvergne 
and  Cantal  in  Central  France  seem  to  have  commenced  their  erup- 
tions in  the  Upper  Eocene  period,  but  to  have  been  most  active 
during  the  Miocene  and  Pliocene  eras.  I  have  already  alluded  to 
the  grand  succession  of  events,  of  which  there  is  evidence  in 
Auvergne  since  the  last  retreat  of  the  sea  (see  p.  197.). 

The  earliest  monuments  of  the  tertiary  period  in  that  region  are 
lacustrine  deposits  of  great  thickness  (2.  fig.  676.  p.  552.),  in  the 
lowest  conglomerates  of  which  are  rounded  pebbles  of  quartz,  mica- 
schist,  granite,  and  other  non-volcanic  rocks,  without  the  slightest 
intermixture  of  igneous  products.  To  these  conglomerates  succeed 
argillaceous  and  calcareous  marls  and  limestones  (3.  fig.  676.),  con- 
taining Upper  Eocene  shells  and  bones  of  mammalia,  the  higher  beds 
of  which  sometimes  alternate  with  volcanic  tuff  of  contemporaneous 
origin.  After  the  filling  up  or  drainage  of  the  ancient  lakes,  huge 
piles  of  trachytic  and  basaltic  rocks,  with  volcanic  breccias,  accu- 
mulated to  a  thickness  of  several  thousand  feet,  and  were  super- 
imposed upon  granite,  or  the  contiguous  lacustrine  strata.  The 
greater  portion  of  these  igneous  rocks  appear  to  have  originated 
during  the  Miocene  and  Pliocene  periods ;  and  extinct  quadrupeds  of 
those  eras,  belonging  to  the  genera  Mastodon,  Rhinoceros,  and  others, 
were  buried  in  ashes  and  beds  of  alluvial  sand  and  gravel,  which  owe 
their  preservation  to  overspreading  sheets  of  lava. 

In  Auvergne  the  most  ancient  and  conspicuous  of  the  volcanic 
masses  is  Mont  Dor,  which  rests  immediately  on  the  granitic  rocks 
standing  apart  from  the  freshwater  strata.*  This  great  mountain 
rises  suddenly  to  the  height  of  several  thousand  feet  above  the  sur- 
rounding platform,  and  retains  the  shape  of  a  flattened  and  somewhat 

*  See  the  Map,  p.  196. 


Cff^  XXXII.]  MONT   DOR,    AUVERGNE.  551 

irregular  cone,  all  the  sides  sloping  more  or  less  rapidly,  until  their 
inclination  is  gradually  lost  in  the  high  plain  around.  This  cone  is 
composed  of  layers  of  scorise,  pumice-stones,  and  their  fine  detritus, 
with  interposed  beds  of  trachyte  and  basalt,  which  descend  often  in 
uninterrupted  sheets,  until  they  reach  and  spread  themselves  round 
the  base  of  the  mountain.*  Conglomerates,  also,  composed  of  angu- 
lar and  rounded  fragments  of  igneous  rocks,  are  observed  to  alter- 
nate with  the  above  ;  and  the  various  masses  are  seen  to  dip  off  from 
the  central  axis,  and  to  lie  parallel  to  the  sloping  flanks  of  the 
mountain. 

The  summit  of  Mont  Dor  terminates  in  seven  or  eight  rocky  peaks, 
where  no  regular  crater  can  now  be  traced,  but  where  we  may  easily 
imagine  one  to  have  existed,  which  may  have  been  shattered  by 
earthquakes,  and  have  suffered  degradation  by  aqueous  agents.  Ori- 
ginally, perhaps,  like  the  highest  crater  of  Etna,  it  may  have  formed 
an  insignificant  feature  in  the  great  pile,  and  may  frequently  have 
been  destroyed  and  renovated.  ' 

According  to  some  geologists,  this  mountain,  as  well  as  Vesuvius, 
Etna,  and  all  large  volcanos,  has  derived  its  dome-like  form  not  from 
the  preponderance  of  eruptions  from  one  or  more  central  points,  but 
from  the  upheaval  of  horizontal  beds  of  lava  and  scoriae.  I  have 
explained  my  reasons  for  objecting  to  this  view  in  Chap.  XXIX., 
when  speaking  of  Palma,  and  in  the  Principles  of  Geology. f  The 
average  inclination  of  the  dome-shaped  mass  of  Mont  Dor  is  8°  6', 
whereas  in  Mounts  Loa  and  Kea,  before  mentioned,  in  the  Sandwich 
Islands  (see  fig.  640.  p.  494.),  the  flanks  of  which  have  been  raised 
by  recent  lavas,  we  find  from  Mr.  Dana's  description  that  the  one 
has  a  slope  of  6°  30',  the  other  of  7°  46'.  We  may,  therefore, 
reasonably  question  whether  there  is  any  absolute  necessity  for  sup- 
posing that  the  basaltic  currents  of  the  ancient  French  volcano  were 
at  first  more  horizontal  than  they  are  now.  Nevertheless  it  is  highly 
probable  that  during  the  long  series  of  eruptions  required  to  give 
rise  to  so  vast  a  pile  of  volcanic  matter,  which  is  thickest  at  the 
summit  or  centre  of  the  dome,  some  dislocation  and  upheaval  took 
place ;  and  during  the  distension  of  the  mass,  beds  of  lava  and  scorise 
may,  in  some  places,  have  acquired  a  greater,  in  others  a  less  incli- 
nation, than  that  which  at  first  belonged  to  them. 

Respecting  the  age  of  the  great  mass  of  Mont  Dor,  we  cannot 
come  at  present  to  any  positive  decision,  because  no  organic  remains 
have  yet  been  found  in  the  tuffs,  except  impressions  of  the  leaves  of 
trees  of  species  not  yet  determined.  We  may  certainly  conclude,  that 
the  earliest  eruptions  were  posterior  in  origin  to  those  grits  and  con- 
glomerates of  the  freshwater  formation  of  the  Limagne  which  contain 
no  pebbles  of  volcanic  rocks ;  while,  on  the  other  hand,  some  erun- 
tions  took  place  before  the  great  lakes  were  drained,  and  others 

*  Scrope's  Central  France,  p.  98.  f  See  chaps,  xxiv.,  xxv.,  and  xxvi., 

7th,  8th,  and  9th  editions. 

NN   4 


552  TERTIARY   VOLCANIC   ROCKS.  [Cn.  XXXII. 

occurred  after  the  desiccation  of  those  lakes,  and  when  deep  valleys 
had  already  been  excavated  through  freshwater  strata. 

In  the  annexed  section,  I  have  endeavoured  to  explain  the  geological 
structure  of  a  portion  of  Auvergne,  which  I  re-examined  in  1843.* 


Valley  of  the        Tour  de 

.Allier.  Boulade. 

Couze  R. 


1  2 

Section  from  the  valley  of  the  Couze  at  Nechers,  through  Mont  Perrier  and  Issoire,  to  the  Valley 
of  the  Allier  and  the  Tour  de  Boulade,  Auvergne. 

10.  Lava-current  of  Tartaret  near  its  tenni-  5.  Lower  bone-bed  of  Perrier,  ochreous  sand 
nation  at  Nechers.  and  gravel. 

9.  Bone-bed,  red  sandy  clay  under  the  lava  of  4  a.  Basaltic  dike. 

Tartaret.  4.  Basaltic  platform. 

8.  Bone-bed  of  the  Tour  de  Boulade.  3.  Upper  freshwater  beds,  limestone,  marl,  gyp- 

7.  Alluvium  newer  than  No.  6.  sum,  &c. 

6.  Alluvium  with  bones  of  hippopotamus.  2.  Lower  freshwater  formation,  red  clay,  green 

5  c.  Trachytic  breccia  resembling  5  a.  sand,  &c. 

5  b.  Upper  bone-bed  of  Perrier,  gravel,  &c.  1.  Granite. 

5«.  Pumiceous  breccia  and  conglomerate,  angu- 
lar masses  of  trachyte,  quartz,  pebbles,  &c. 

It  may  convey  some  idea  to  the  reader  of  the  long  and  complicated 
series  of  events,  which  have  occurred  in  that  country,  since  the  first 
lacustrine  strata  (No.  2.)  were  deposited  on  the  granite  (No.  1.).  The 
changes  of  which  we  have  evidence  are  the  more  striking,  because 
they  imply  great  denudation,  without  there  being  any  proofs  of  the 
intervention  of  the  sea  during  the  whole  period.  It  will  be  seen 
that  the  upper  freshwater  beds  (No.  3.),  once  formed  in  a  lake,  must 
have  suffered  great  destruction  before  the  excavation  of  the  valleys  of 
the  Couze  and  Allier  had  begun.  In  these  freshwater  beds,  Upper 
Eocene  fossils,  as  described  in  Chap.  XV.,  have  been  found.  The 
basaltic  dike,  4',  is  one  of  many  examples  of  the  intrusion  of  volcanic 
matter  through  the  Eocene  freshwater  beds,  and  may  have  been  of 
Upper  Eocene  or  Miocene  date,  giving  rise,  when  it  reached  the 
surface  and  overflowed,  to  such  platforms  of  basalt,  as  often  cap  the 
tertiary  hills  in  Auvergne,  and  one  of  which  (4)  is  seen  on  Mont 
Perrier. 

It  not  unfrequently  happens  that  beds  of  gravel  containing  bones 
of  extinct  mammalia  are  detected  under  these  very  ancient  sheets  of 
basalt,  as  between  No.  4.  and  the  freshwater  strata,  No.  3.,  at  A,  from 
which  it  is  clear  that  the  surface  of  No.  3.  formed  at  that  period  the 
lowest  level  at  which  the  waters  then  draining  the  country  flowed. 
Next  in  age  to  this  basaltic  platform  comes  a  patch  of  ochreous  sand 
and  gravel  (No.  5.),  containing  many  bones  of  quadrupeds.  Upon 
this  rests  a  pumiceous  breccia  or  conglomerate,  with  angular  masses 
of  trachyte  and  some  quartz  pebbles.  This  deposit  is  followed  by  5  b 
(which  is  similar  to  5)  and  5  c  similar  to  the  trachytic  breccia  5  a. 
These  two  breccias  are  supposed,  from  their  similarity  to  others  found 
on  Mont  Dor,  to  have  descended  from  the  flanks  of  that  mountain 

*  See  Quarterly  Geol.  Journ.  vol.  ii.  p.  77. 


CH;  XXXII.]  VOLCANOS   OF   AUVERGNE.  553 

during  eruptions  ;  and  the  interstratified  alluvial  deposits  contain  the 
remains  of  mastodon,  rhinoceros,  tapir,  deer,  beaver,  and  quadrupeds 
of  other  genera,  referable  to  about  forty  species,  all  of  which  are 
extinct.  I  formerly  supposed  them  to  belong  to  the  same  era  as  the 
Miocene  faluns  of  Touraine ;  but,  whether  they  may  not  rather  be 
ascribed  to  the  older  Pliocene  epoch  is  a  question  which  farther  in- 
quiries and  comparisons  must  determine. 

Whatever  be  their  date  in  the  tertiary  series,  they  are  quadrupeds 
which  inhabited  the  country  when  the  formations  5  and  5  c  ori- 
ginated. Probably  they  were  drowned  during  floods,  such  as  rush 
down  the  flanks  of  volcanos  during  eruptions,  when  great  bodies  of 
steam  are  emitted  from  the  crater,  or  when,  as  we  have  seen,  both  on 
Etna  and  in  Iceland  in  modern  times,  large  masses  of  snow  are  sud- 
denly melted  by  lava,  causing  a  deluge  of  water  to  bear  down  frag- 
ments of  igneous  rocks  mixed  with  mud  to  the  valleys  and  plains 
below. 

It  will  be  seen  that  the  valley  of  the  Issoice,  down  which  these 
ancient  inundations  swept,  was  first  excavated  at  the  expense  of  the 
formations  2,  3,  and  4,  and  then  filled  up  by  the  masses  5  and  5  c, 
after  which  it  was  re-excavated  before  the  more  modern  alluviums 
(Nos.  6.  and  7.)  were  formed.  In  these  again  other  fossil  mammalia 
of  distinct  species  have  been  detected  by  M.Bravard,  the  bones  of  an 
hippopotamus  having  been  found  among  the  rest. 

At  length,  when  the  valley  of  the  Allier  was  eroded  at  Issoire  down 
to  its  lowest  level,  a  talus  of  angular  fragments  of  basalt  and  fresh- 
water limestone  (No.  8.)  was  formed,  called  the  bone-bed  of  the  Tour 
de  Boulade,  from  which  a  great  many  other  mammalia  have  been 
collected  by  MM.  Bravard  and  Pomel.  In  this  assemblage  the  Ele- 
phas  primigenius,  Rhinoceros  tichorinus,  Deer  (including  rein-deer), 
Equus,  Bos,  Antelope,  Felis,  and  Canis  were  included.  Even  this 
deposit  seems  hardly  to  be  the  newest  in  the  neighbourhood,  for  if  we 
cross  from  the  town  of  Issoire  (see  fig.  676.)  over  Mont  Perrier  to  the 
adjoining  valley  of  the  Couze,  we  find  another  bone-bed  (No.  9.), 
overlaid  by  a  current  of  lava  (No.  10.). 

The  history  of  this  lava-current,  which  terminates  a  few  hundred 
yards  below  the  point  No.  10.,  in  the  suburbs  of  the  village  of  Nechers, 
is  interesting.  It  forms  a  long  narrow  stripe  more  than  13  miles  in 
length,  at  the  bottom  of  the  valley  of  the  Couze,  which  flows  out  of  a 
lake  at  the  foot  of  Mont  Dor.  This  lake  is  caused  by  a  barrier 
thrown  across  the  ancient  channel  of  the  Couze,  consisting  partly  of' 
the  volcanic  cone  called  the  Puy  de  Tartaret,  formed  of  loose  scoriae, 
from  the  base  of  which  has  issued  the  lava-current  before  mentioned. 
The  materials  of  the  dam  which  blocked  up  the  river,  and  caused  the 
Lac  de  Chambon,  are  also,  in  part,  derived  from  a  land-slip  which  may 
have  happened  at  the  time  of  the  great  eruption  which  formed  the  cone. 

This  cone  of  Tartaret  affords  an  impressive  monument  of  the  very 
different  dates  at  which  the  igneous  eruptions  of  Auvergne  have 
happened ;  for  it  was  evidently  thrown  up  at  the  bottom  of  the  exist- 
ing valley,  which  is  bounded  by  lofty  precipices  composed  of  sheets 


554  TERTIARY   VOLCANIC    ROCKS.  [Cn.  XXXII. 

of  ancient  columnar  trachyte  and  basalt,  which  once  flowed  at  very 
high  levels  from  Mont  Dor.* 

When  we  follow  the  course  of  the  river  Couze,  from  its  source  in 
the  lake  of  Chambon  to  the  termination  of  the  lava-current  at 
Nechers,  a  distance  of  thirteen  miles,  we  find  that  the  torrent  has  in 
most  places  cut  a  deep  channel  through  the  lava,  the  lower  portion  of 
which  is  columnar.  In  some  narrow  gorges  the  water  has  even  had 
power  to  remove  the  entire  mass  of  basaltic  rock,  though  the  work  of 
erosion  must  have  been  very  slow,  as  the  basalt  is  tough  and  hard,  and 
one  column  after  another  must  have  been  undermined  and  reduced 
to  pebbles,  and  then  to  sand.  During  the  time  required  for  this 
operation,  the  perishable  cone  of  Tartaret,  composed  of  sand  and 
ashes,  has  stood  uninjured,  proving  that  no  great  flood  or  deluge  can 
have  passed  over  this  region  in  the  interval  between  the  eruption  of 
Tartaret  and  our  own  times. 

If  we  now  return  to  the  section  (fig.  676.),  I  may  observe  that  the 
lava-current  of  Tartaret,  which  has  diminished  greatly  in  height  and 
volume  near  its  termination,  presents  here  a  steep  and  perpendicular 
face  25  feet  in  height  towards  the  river.  Beneath  it  is  the  alluvium 
No.  9.,  consisting  of  a  red  sandy  clay,  which  must  have  covered  the 
bottom  of  the  valley  when  the  current  of  melted  rock  flowed  down. 
The  bones  found  in  this  alluvium,  which  I  obtained  myself,  consisted 
of  a  species  of  field-mouse,  Arvicola,  and  the  molar  tooth  of  an  ex- 
tinct horse,  Equus  fossilis.  The  other  species,  obtained  from  the 
same  bed,  are  referable  to  the  genera  Sus,  Bos,  Cervus,  Felis,  Canis, 
Maries,  Talpa,  Sorex,  Lepus,  Sciurus,  Mus,  and  Lagomys,  in  all  no 
less  than  forty-three  species,  all  closely  allied  to  recent  animals,  yet 
nearly  all  of  them,  according  to  M.  Bravard,  showing  some  points  of 
difference,  like  those  which  Mr.  Owen  discovered  in  the  case  of  the 
horse  above  alluded  to.  The  bones,  also  of  a  frog,  snake,  and  lizard, 
and  of  several  birds,  were  associated  with  the  fossils  before  enumerated, 
and  several  recent  land  shells,  such  as  Cyclostoma  elegans,  Helix  hor- 
tensis,  H.  nemoralis,  H.  lapicida,  and  Clausilia  rugosa.  If  the 
animals  were  drowned  by  floods,  which  accompanied  the  eruptions  of 
the  Puy  de  Tartaret,  they  would  give  an  exceedingly  modern  geolo- 
gical date  to  that  event,  which  must,  in  that  case,  have  belonged  to 
the  Newer-Pliocene,  or,  perhaps,  the  Post-Pliocene  period.  That  the 
current  which  has  issued  from  the  Puy  de  Tartaret,  may  nevertheless 
be  very  ancient  in  reference  to  the  events  of  human  history,  we  may 
conclude,  not  only  from  the  divergence  of  the  mammiferous  fauna 
from  that  of  our  day,  but  from  the  fact  that  a  Roman  bridge  of  such 
form  and  construction  as  continued  in  use  down  to  the  fifth  century, 
but  which  may  be  older,  is  now  seen  at  a  place  about  a  mile  and  a 
half  from  St.  Nectaire.  This  ancient  bridge  spans  the  river  Couze 
with  two  arches,  each  about  14  feet  wide.  These  arches  spring  from 
the  lava  of  Tartaret,  on  both  banks,  showing  that  a  ravine  precisely 

*  For  a  view  of  Puy  de  Tartaret  and  Mont  Dor,  see   Scrope's  Volcanos  of 
Central  France. 


C'H.  XXXII.]  VOLCANOS   OF    AUVERGNE.  555 

like  that  now  existing,  had   already  been  excavated  by  the  river 
through  that  lava  thirteen  or  fourteen  centuries  ago. 

In  Central  France  there  are  several'  hundred  minor  cones,  like  that 
of  Tartaret,  a  great  number  of  which,  like  Monte  Nuovo,  near  Naples, 
may  have  been  principally  due  to  a  single  eruption.  Most  of  these 
cones  range  in  a  linear  direction  from  Auvergne  to  the  Vivarais,  and 
they  were  faithfully  described  so  early  as  the  year  1802,  by  M.  de 
Montlosier.  They  have  given  rise  chiefly  to  currents  of  basaltic 
lava.  Those  of  Auvergne  called  the  Monts  Dome,  placed  on  a  gra- 
nitic platform,  form  an  irregular  ridge  (see  fig.  621.  p.  466.),  about  18 
miles  in  length  and  2  in  breadth.  They  are  usually  truncated  at 
the  summit,  where  the  crater  is  often  preserved  entire,  the  lava  having 
issued  from  the  base  of  the  hill.  But  frequently  the  crater  is  broken 
down  on  one  side,  where  the  lava  has  flowed  out.  The  hills  are  com- 
posed of  loose  scoriae,  blocks  of  lava,  lapilli,  and  pozzuolana,  with 
fragments  of  trachyte  and  granite. 

Puy  de  Come. — The  Puy  de  Come  and  its  lava-current,  near 
Clermont,  may  be  mentioned  as  one  of  these  minor  volcanos.  This 
conical  hill  rises  from  the  granitic  platform,  at  an  angle  of  between 
30°  and  40°,  to  the  height  of  more  than  900  feet.  Its  summit  pre- 
sents two  distinct  craters,  one  of  them  with  a  vertical  depth  of  250 
feet.  A  stream  of  lava  takes  its  rise  at  the  western  base  of  the  hill, 
instead  of  issuing  from  either  crater,  and  descends  the  granitic  slope 
towards  the  present  site  of  the  town  of  Pont  Gibaud.  Thence  it 
pours  in  a  broad  sheet  down  a  steep  declivity  into  the  valley  of  the 
Sioule,  filling  the  ancient  river-channel  for  the  distance  of  more  than 
a  mile.  The  Sioule,  thus  dispossessed  of  its  bed,  has  worked  out  a 
fresh  one  between  the  lava  and  the  granite  of  its  western  bank  4  and 
the  excavation  has  disclosed,  in  one  spot,  a  wall  of  columnar  basalt 
about  50  feet  high.* 

The  excavation  of  the  ravine  is  still  in  progress,  every  winter  some 
columns  of  basalt  being  undermined  and  carried  down  the  channel 
of  the  river,  and  in  the  course  of  a  few  miles  rolled  to  sand  and 
pebbles.  Meanwhile  the  cone  of  Come  remains  unimpaired*  its 
loose  materials  being  protected  by  a  dense  vegetation,  and  the  hill 
standing  on  a  ridge  not  commanded  by  any  higher  ground,  so  that  no 
floods  of  rain-water  can  descend  upon  it.  There  is  no  end  to  the 
waste  which  the  hard  basalt  may  undergo  in  future,  if  the  physical 
geography  of  the  country  continue  unchanged,  no  limit  to  the  number 
of  years  during  which  the  heap  of  incoherent  and  transportable 
materials  called  the  Puy  de  Come  may  remain  in  a  stationary  con- 
dition. In  this  place,  therefore,  we  behold  in  the  results  of  aqueous 
and  atmospheric  agency  in  past  times,  a  counterpart  of  what  we 
must  expect  to  recur  in  future  ages. 

Lava  of  Chaluzet. — At  another  point,  farther  down  the  course  of 
the  Sioule,  we  find  a  second  illustration  of  the  same  phenomenon  in 
the  Puy  Rouge,  a  conical  hill  to  the  north  of  the  village  of  Pranal. 

*  Scrope's  Central  France,  p.  60.,  and  plate. 


556 


TERTIARY  VOLCANIC  ROCKS. 


[CH.  XXXII. 


The  cone  is  composed  entirely  of  red  and  black  scoriae,  tuff,  and  vol- 
canic bombs.  On  its  western  side,  towards  the  village  of  Chaluzet, 
there  is  a  worn -down  crater,  whence  a  powerful  stream  of  lava  has 
issued,  and  flowed  into  the  valley  of  the  Sioule.  The  river  has  since 
excavated  a  ravine  through  the  lava  and  subjacent  gneiss,  to  the 
depth  in  some  places  of  400  feet. 

On  the  upper  part  of  the  precipice  forming  the  left  side  of  this 
ravine,  we  see  a  great  mass  of  black  and  red  scoriaceous  lava  be- 
coming more  and  more  columnar  towards  its  base.  (See  fig.  677.). 

Fig.  677. 


a.  Scoriaceous  lava. 

b.  Columnar  basalt. 

c.  Gravel. 

D.  Ancient  mining  gallery. 

E.  Pathway. 
/.  Gneiss. 


Lava-current  of  Chaluzet,  Auvergne,  near  its  termination.* 

Below  this  is  a  bed  of  sand  and  gravel  3  feet  thick,  evidently  an 
ancient  river-bed,  now  at  an  elevation  of  25  feet  above  the  channel 
of  the  Sioule.  This  gravel,  from  which  water  gushes  out,  rests  upon 
gneiss,  f,  which  has  been  eroded  to  the  depth  of  25  feet  at  the  point 
where  the  annexed  view  is  taken.  At  D,  close  to  the  village  of  Les 
Combres,  the  entrance  of  a  gallery  is  seen,  in  which  lead  has  been 
worked  in  the  gneiss.  This  mine  shows  that  the  pebble-bed  is  con- 
tinuous, in  a  horizontal  direction,  between  the  gneiss  and  the  volcanic 
mass.  Here  again  it  is  quite  evident,  that,  while  the  basalt  was  gra- 
dually undermined  and  carried  away  by  the  force  of  running  water, 
the  cone  whence  the  lava  issued  escaped  destruction,  because  it  stood 
upon  a  platform  of  gneiss  several  hundred  feet  above  the  level  of  the 
valley  in  which  the  force  of  running  water  was  exerted. 

Puy  de  Pariou. — The  brim  of  the  crater  of  the  Puy  de  Pariou, 
near  Clermont,  is  so  sharp,  and  has  been  so  little  blunted  by  time, 
that  it  scarcely  affords  room  to  stand  upon.  This  and  other  cones 


Lyell  and  Murchison,  Ed.  New  Phil.  Journ.  1829. 


CH.  XXXII.]  VELAY,    CANTAL.  557 

in  an  equally  remarkable  state  of  integrity  have  stood,  I  conceive, 
uninjured,  not  in  spite  of  their  loose  porous  nature,  as  might  at  first 
be  naturally  supposed,  but  in  consequence  of  it.  No  rills  can  collect 
where  all  the  rain  is  instantly  absorbed  by  the  sand  and  scoriae,  as  is 
remarkably  the  case  on  Etna ;  and  nothing  but  a  waterspout  break- 
ing directly  upon  the  Puy  de  Pariou  could  carry  away  a  portion  of 
the  hill,  so  long  as  it  is  not  rent  or  engulphed  by  earthquakes. 

Hence  it  is  conceivable  that  even  those  cones  which  have  the 
freshest  aspect  and  most  perfect  shape  may  lay  claim  to  very  high 
antiquity.  Dr.  Daubeny  has  justly  observed,  that  had  any  of  these 
volcanos  been  in  a  state  of  activity  in  the  age  of  Julius  Caesar,  that 
general,  who  encamped  upon  the  plains  of  Auvergne,  and  laid  siege 
to  its  principal  city  (Gergovia,  near  Clermont),  could  hardly  have 
failed  to  notice  them.  Had  there  been  any  record  of  their  eruptions 
in  the  time  of  Pliny  or  Sidonius  Apollinaris,  the  one  would  scarcely 
have  omitted  to  make  mention  of  it  in  his  Natural  History,  nor  the 
other  to  introduce  some  allusion  to  it  among  the  descriptions  of  this 
his  native  province.  This  poet's  residence  was  on  the  borders  of  the 
Lake  Aidat,  which  owed  its  very  existence  to  the  damming  up  of  a 
river  by  one  of  the  most  modern  lava-currents.* 

Velay. — The  observations  of  M.  Bertrand  de  Doue  have  not  yet 
established  that  any  of  the  most  ancient  volcanos  of  Velay  were  in 
action  during  the  Eocene  period.  There  are  beds  of  gravel  in  Velay, 
as  in  Auvergne,  covered  by  lava  at  different  heights  above  the  chan- 
nel of  the  existing  rivers.  In  the  highest  and  most  ancient  of  these 
alluviums  the  pebbles  are  exclusively  of  granitic  rocks  ;  but  in  the 
newer,  which  are  found  at  lower  levels,  and  which  originated  when 
the  valleys  had  been  cut  to  a  greater  depth,  an  intermixture  of  vol- 
canic rocks  has  been  observed. 

At  St.  Privat  d'Allier  a  bed  of  volcanic  scoriae  and  tuff  was  dis- 
covered by  Dr.  Hibbert,  inclosed  between  two  sheets  of  basaltic  lava ; 
and  in  this  tuff  were  found  the  bones  of  several  quadrupeds,  some  of 
them  adhering  to  masses  of  slaggy  lava.  Among  other  animals  were 
Rhinoceros  leptorhinus,  Hyana  spelcea,  and  a  species  allied  to  the 
spotted  hyaena  of  the  Cape,  together  with  four  undetermined  species 
of  deer.  The  manner  of  the  occurrence  of  these  bones  reminds  us 
of  the  published  accounts  of  an  eruption  of  Coseguina,  1835,  in 
Central  America  (see  p.  525.),  during  which  hot  cinders  and  scoriae 
fell  and  scorched  to  death  great  numbers  of  wild  and  domestic  ani- 
mals and  birds. 

Plomb  du  Cantal. — In  regard  to  the  age  of  the  igneous  rocks  of 
the  Cantal,  we  can  at  present  merely  affirm,  that  they  overlie  the 
(Upper?)  Eocene  lacustrine  strata  of  that  country  (see  Map,  p.  196.). 
They  form  a  great  'dome-shaped  mass,  having  an  average  slope  of 
only  4°,  which  has  evidently  been  accumulated,  like  the  cone  of 
Etna,  during  a  long  series  of  eruptions.  It  is  composed  of  trachytic, 
phonolitic,  arid  basaltic  lavas,  tuffs,  and  conglomerates,  or  breccias, 

*  Daubeny  on  Volcanos,  p.  14. 


558  EOCENE   VOLCANIC   ROCKS.  [CH.  XXXII. 

forming  a  mountain  several  thousand  feet  in  height.  Dikes  also  of 
phonolite,  trachyte,  and  basalt  are  numerous,  especially  in  the  neigh- 
bourhood of  the  large  cavity,  probably  once  a  crater,  around  which 
the  loftiest  summits  of  the  Cantal  are  ranged  circularly,  few  of  them, 
except  the  Plomb  du  Cantal,  rising  far  above  the  border  or  ridge  of 
this  supposed  crater.  A  pyramidal  hill,  called  the  Puy  Griou,  occu- 
pies the  middle  of  the  cavity.*  It  is  clear  that  the  volcano  of  the 
Cantal  broke  out  precisely  on  the  site  of  the  lacustrine  deposit  be- 
fore described  (p.  205.),  which  had  accumulated  in  a  depression  of  a 
tract  composed  of  micaceous  schist.  In  the  breccias,  even  to  the 
very  summit  of  the  mountain,  we  find  ejected  masses  of  the  fresh- 
water beds,  and  sometimes  fragments  of  flint,  containing  Eocene 
shells.  Valleys  radiate  in  all  directions  from  the  central  heights  of 
the  mountain,  increasing  in  size  as  they  recede  from  those  heights. 
Those  of  the  Cer  and  Jourdanne,  which  are  more  than  20  miles  in 
length,  are  of  great  depth,  and  lay  open  the  geological  structure 
of  the  mountain.  No  alternation  of  lavas  with  undisturbed  Eocene 
strata  has  been  observed,  nor  any  tuffs  containing  freshwater  shells, 
although  some  of  these  tuffs  include  fossil  remains  of  terrestrial 
plants,  said  to  imply  several  distinct  restorations  of  the  vegetation 
of  the  mountain  in  the  intervals  between  great  eruptions.  On  the 
northern  side  of  the  Plomb  du  Cantal,  at  La  Vissiere,  near  Murat,  is 
a  spot,  pointed  out  on  the  Map  (p.  196.),  where  freshwater  limestone 
and  marl  are  seen  covered  by  a  thickness  of  about  800  feet  of  vol- 
canic rock.  Shifts  are  here  seen  in  the  strata  of  limestone  and 
marl.f 

In  treating  of  the  lacustrine  deposits  of  Central  France,  in  the 
fifteenth  chapter,  it  was  stated  that,  in  the  arenaceous  and  pebbly 
group  of  the  lacustrine  basins  of  Auvergne,  Cantal,  and  Velay,  no 
volcanic  pebbles  had  ever  been  detected,  although  massive  piles  of 
igneous  rocks  are  now  found  in  the  immediate  vicinity.  As  this 
observation  has  been  confirmed  by  minute  research,  we  are  warranted 
in  inferring  that  the  volcanic  eruptions  had  not  commenced  when 
the  older  subdivisions  of  the  freshwater  groups  originated. 

In  Cantal  and  Velay  no  decisive  proofs  have  yet  been  brought  to 
light  that  any  of  the  igneous  outbursts  happened  during  the  depo- 
sition of  the  freshwater  strata ;  but  there  can  be  no  doubt  that  in 
Auvergne  some  volcanic  explosions  took  place  before  the  drainage 
of  the  lakes,  and  at  a  time  when  the  Upper  Eocene  species  of  animals 
and  plants  still  flourished.  Thus,  for  example,  at  Pont  du  Chateau, 
near  Clermont,  a  section  is  seen  in  a  precipice  on  the  right  bank  of 
the  river  Allier,  in  which  beds  of  volcanic  tuff  alternate  with  a  fresh- 
water limestone,  which  is  in  some  places  pure,  but  in  others  spotted 
with  fragments  of  volcanic  matter,  as  if  it  were  deposited  while 
showers  of  sand  and  scoriae  were  projected  from  a  neighbouring 
vent.f 

*  Mem.  de  la  Soc.  G£ol.  de  France,  f  See  Lyell  and  Murchison,  Ann.  de 
torn.  i.  p.  175.  Sci.  Nat.,  Oct.  1829. 

|  See  Scrope's  Central  France,  p.  21. 


CH.  XXXII.] 


GERGOVIA. 


559 


Another  example  occurs  in  the  Puy  de  Marmont,  near  Veyres, 
where  a  freshwater  marl  alternates  with  volcanic  tuff  containing 
Eocene  shells.  The  tuff  or  breccia  in  this  locality  is  precisely  such 
as  is  known  to  result  from  volcanic  ashes  falling  into  water,  and  sub- 
siding together  with  ejected  fragments  of  marl  and  other  stratified 
rocks.  These  tuffs  and  marls  are  highly  inclined,  and  traversed  by 
a  thick  vein  of  basalt,  which,  as  it  rises  in  the  hill,  divides  into  two 
branches. 

Gergovia.  —  The  hill  of  Gergovia,  near  Clermont,  affords  a  third 
example.  I  agree  with  MM.  Dufrenoy  and  Jobert  that  there  is  no 
alternation  here  of  a  contemporaneous  sheet  of  lava  with  freshwater 
strata,  in  the  manner  supposed  by  some  other  observers  * ;  but  the 
position  and  contents  of  some  of  the  associated  tuffs,  prove  them  to 
have  been  derived  from  volcanic  eruptions  which  occurred  during  the 
deposition  of  the  lacustrine  strata. 

The  bottom  of  the  hill  consists  of  slightly  inclined  beds  of  white 
and  greenish  marls,  more  than  300  feet  in  thickness,  intersected  by  a 
dike  of  basalt,  which  may  be  studied  in  the  ravine  above  the  village 
of  Merdogne.  The  dike  here  cuts  through  the  marly  strata  at  a  con- 
siderable angle,  producing,  in  general,  great  alteration  and  confusion 
in  them  for  some  distance  from  the  point  of  contact.  Above  the 

Fig.  678. 


White 
and  green 
marls. 


Hill  of  Gergovia. 

white  and  green  marls,  a  series  of  beds  of  limestone  and  marl,  con- 
taining freshwater  shells,  are  seen  to  alternate  with  volcanic  tuff. 
In  the  lowest  part  of  this  division,  beds  of  pure  marl  alternate  with 
compact  fissile  tuff,  resembling  some  of  the  subaqueous  tuffs  of  Italy 
and  Sicily  called  peperinos.  Occasionally  fragments  of  scoriae  are 
visible  in  this  rock.  Still  higher  is  seen  another  group  of  some 
thickness,  consisting  exclusively  of  tuff,  upon  which  lie  other  marly 
strata  intermixed  with  volcanic  matter.  Among  the  species  of  fossil 
shells  which  I  found  in  these  strata  were  Melania  inquinata,  a  Unio, 

*  See  Scrope's  Central  France,  p.  7. 


560  CRETACEOUS   VOLCANIC   ROCKS.  [Cn.  XXXII. 

and  a  Melanopsis,  but  they  were  not  sufficient  to  enable  me  to  deter- 
mine with  precision  the  age  of  the  formation. 

There  are  many  points  in  Auvergne  where  igneous  rocks  have 
been  forced  by  subsequent  injection  through  clays  and  marly  lime- 
stones, in  such  a  manner  that  the  whole  has  become  blended  in  one 
confused  and  brecciated  mass,  between  which  and  the  basalt  there  is 
sometimes  no  very  distinct  line  of  demarcation.  In  the  cavities  of 
such  mixed  rocks  we  often  find  calcedony,  and  crystals  of  mesotype, 
stilbite,  and  arragonite.  To  formations  of  this  class  may  belong  some 
of  the  breccias  immediately  adjoining  the  dike  in  the  hill  of  Ger- 
govia  ;  but  it  cannot  be  contended  that  the  volcanic  sand  and  scorias 
interstratified  with  the  marls  and  limestones  in  the  upper  part  of  that 
hill  were  introduced,  like  the  dike,  subsequently,  by  intrusion  from 
below.  They  must  have  been  thrown  down  like  sediment  from  water, 
and  can  only  have  resulted  from  igneous  action,  which  was  going 
on  contemporaneously  with  the  deposition  of  the  lacustrine  strata. 

The  reader  will  bear  in  mind  that  this  conclusion  agrees  well  with 
the  proofs,  adverted  to  in  the  fifteenth  chapter,  of  the  abundance  of 
silex,  travertin,  and  gypsum  precipitated  when  the  upper  lacustrine 
strata  were  formed ;  for  these  rocks  are  such  as  the  waters  of  mineral 
and  thermal  springs  might  generate. 

Cretaceous  period.  —  Although  we  have  no  proof  of  volcanic  rocks 
erupted  in  England  during  the  deposition  of  the  chalk  and  greensand, 
it  would  be  an  error  to  suppose  that  no  theatres  of  igneous  action 
existed  in  the  cretaceous  period.  M.  Virlet,  in  his  account  of  the 
geology  of  the  Morea,  p.  205.,  has  clearly  shown  that  certain  traps 
in  Greece,  called  by  him  ophiolites,  are  of  this  date ;  as  those,  for 
example,  which  alternate  conformably  with  cretaceous  limestone  and 
greensand  between  Kastri  and  Damala  in  the  Morea.  They  consist 
in  great  part  of  diallage  rocks  and  serpentine,  and  of  an  amygdaloid 
with  calcareous  kernels,  and  a  base  of  serpentine. 

In  certain  parts  of  the  Morea,  the  age  of  these  volcanic  rocks  is 
established  by  the  following  proofs :  first,  the  lithographic  limestones 
of  the  Cretaceous  era  are  cut  through  by  trap,  and  then  a  conglo- 
merate occurs,  at  Nauplia  and  other  places,  containing  in  its  calcareous 
cement  many  well-known  fossils  of  the  chalk  and  greensand,  together 
with  pebbles  formed  of  rolled  pieces  of  the  same  ophiolite,  which 
appear  in  the  dikes  above  alluded  to. 

Period  of  Oolite  and  Lias.  —  Although  the  green  and  serpentinous 
trap  rocks  of  the  Morea  belong  chiefly  to  the  Cretaceous  era,  as  before 
mentioned,  yet  it  seems  that  some  eruptions  of  similar  rocks  began 
during  the  Oolitic  period  *  ;  and  it  is  probable,  that  a  large  part  of 
the  trappean  masses,  called  ophiolites  in  the  Apennines,  and  associated 
with  the  limestone  of  that  chain,  are  of  corresponding  age. 

That  some  part  of  the  volcanic  rocks  of  the  Hebrides,  in  our  own 
country,  originated  contemporaneously  with  the  Oolite  which  they 
traverse  and  overlie,  has  been  ascertained  by  Prof.  E.  Forbes,  in 

*  Boblaye  and  Virlet,  Morea,  p.  23. 


CH": XXXII.]      CAEBONIFEROUS   VOLCANIC   KOCKS.  561 

1850.  Some  of  the  eruptions  in  Skye,  for  example,  occurred  at  the 
close  of  the  Middle  and  before  the  commencement  of  the  Upper 
Oolitic  Period.* 

Trap  of  the  New  Red  Sandstone  period. — In  the  southern  part  of 
Devonshire,  trappean  rocks  are  associated  with  New  Red  Sandstone, 
and,  according  to  Sir  H.  de  la  Beche,  have  not  been  intruded  subse- 
quently into  th'e  sandstone,  but  were  produced  by  contemporaneous 
volcanic  action.  Some  beds  of  grit,  mingled  with  ordinary  red  marl, 
resemble  sands  ejected  from  a  crater ;  and  in  the  stratified  conglo- 
merates occurring  near  Tiverton  are  many  angular  fragments  of  trap 
porphyry,  some  of  them  one  or  two  tons  in  weight,  intermingled  with 
pebbles  of  other  rocks.  These  angular  fragments  were  probably 
thrown  out  from  volcanic  vents,  and  fell  upon  sedimentary  matter 
then  in  the  course  of  deposition.")" 

Carboniferous  period.  —  Two  classes  of  contemporaneous  trap 
rocks  have  been  ascertained  by  Dr.  Fleming  to  occur  in  the  coal-field 
of  the  Forth  in  Scotland.  The  newest  of  these,  connected  with  the 
higher  series  of  coal-measures,  is  well  exhibited  along  the  shores  of 
the  Forth,  in  Fifeshire,  where  they  consist  of  basalt  with  olivine, 
amygdaloid,  greenstone,  wacke,  and  tuff.  They  appear  to  have  been 
erupted  while  the  sedimentary  strata  were  in  a  horizontal  position, 
and  to  have  suffered  the  same  dislocations  which  those  strata  have 
subsequently  undergone.  In  the  volcanic  tuffs  of  this  age  are  found 
not  only  fragments  of  limestone,  shale,  flinty  slate,  and  sandstone,  but 
also  pieces  of  coal. 

The  other  or  older  class  of  carboniferous  traps  are  traced  along 
the  south  margin  of  Stratheden,  and  constitute  a  ridge  parallel  with 
the  Ochils,  and  extending  from  Stirling  to  near  St.  Andrews.  They 
consist  almost  exclusively  of  greenstone,  becoming,  in  a  few  instances, 
earthy  and  amygdaloidal.  They  are  regularly  interstratified  with  the 
sandstone,  shale,  and  ironstone  of  the  lower  Coal-measures,  and,  on 
the  East  Lomond,  with  Mountain  Limestone. 

I  examined  these  trap  rocks  in  1838,  in  the  cliffs  south  of  St.  An- 
drews, where  they  consist  in  great  part  of  stratified  tuffs,  which  are 
curved,  vertical,  and  contorted,  like  the  associated  coal-measures.  In 
the  tuff  I  found  fragments  of  carboniferous  shale  and  limestone,  and 
intersecting  veins  of  greenstone.  At  one  spot,  about  two  miles  from 
St.  Andrews,  the  encroachment  of  the  sea  on  the  cliffs  has  isolated 
several  masses  of  trap,  one  of  which  (fig.  679.)  is  aptly  called  the 
"  rock  and  spindle,"  {  for  it  consists  of  a  pinnacle  of  tuff,  which  may 
be  compared  to  a  distaff,  and  near  the  base  is  a  mass  of  columnar 
greenstone,  in  which  the  pillars  radiate  from  a  centre,  and  appear  at 
a  distance  like  the  spokes  of  a  wheel.  The  largest  diameter  of  this 
wheel  is  about  twelve  feet,  and  the  polygonal  terminations  of  the 

*  Geol.   Quart.  Joura.    1851,   vol.  \  "The  rock,"  as  English  readers  of 

vii.  p.  108.  Burns's    poems    may   remember,    is    a 

f  De  la    Beche,    Geol.   Proceedings,      Scotch  term  for  a  distaff, 
vol.  ii.  p.  198. 

OO 


562 


CARBONIFEROUS   VOLCANIC    ROCKS.       [Cn.  XXXII. 
Fig.  679. 


a.  Unstratified  tuff. 


Hock  and  Spindle,  St.  Andrews,  as  seen  in  1838. 
b.  Columnar  greenstone. 


c.  Stratified  tuff. 


Fig.  680. 


columns  are  seen  round  the  circumference  (or  tire, 
as  it  were,  of  the  wheel),  as  in  the  accompany- 
ing figure.  I  conceive  this  mass  to  be  the  ex- 
tremity of  a  string  or  vein  of  greenstone,  which 
penetrated  the  tun0.  The  prisms  point  in  every 
direction,  because  they  were  surrounded  on  all 
sides  by  cooling  surfaces,  to  which  they  always 
arrange  themselves  at  right  angles,  as  before  ex- 
plained (p.  488.). 
A  trap  dike  was  pointed  out  to  me  by  Dr.  Fleming,  in  the  parish 


Columns     of     Green- 
stone, seen  endwise  at 
b,  fig.  679. 


CH.  XXXII.]  SILURIAN   YOLCANIC   ROCKS.  563 

of  Flisk,  in  the  northern  part  of  Fifeshire,  which  cuts  through  the 
grey  sandstone  and  shale  forming  the  lowest  part  of  the  Old  Red 
Sandstone.  It  may  be  traced  for  many  miles,  passing  through  the 
amygdaloidal  and  other  traps  of  the  hill  called  Norman's  Law.  In 
its  course  it  affords  a  good  exemplification  of  the  passage  from  the 
trappean  into  the  plutonic,  or  highly  crystalline  texture.  Professor 
G-ustavus  Rose,  to  whom  I  submitted  specimens  of  this  dike,  finds 
the  rock,  which  he  calls  dolerite,  to  consist  of  greenish  black  augite 
and  Labrador  felspar,  the  latter  being  the  most  abundant  ingredient. 
A  small  quantity  of  magnetic  iron,  perhaps  titaniferous,  is  also 
present.  The  result  of  this  analysis  is  interesting,  because  both  the 
ancient  and  modern  lavas  of  Etna  consist  in  like  manner  of  augite, 
Labradorite,  and  titaniferous  iron. 

Trap  of  the  Old  Red  sandstone  period.  —  By  referring  to  the 
section  explanatory  of  the  structure  of  Forfarshire,  already  given 
(p.  48.),  the  reader  will  perceive  that  beds  of  conglomerate,  No.  3., 
occur  in  the  middle  of  the  Old  Red  sandstone  system,  1,  2,  3,  4. 
The  pebbles  in  these  conglomerates  are  sometimes  composed  of 
granitic  and  quartzose  rocks,  sometimes  exclusively  of  different 
varieties  of  trap,  which,  although  purposely  omitted  in  the  section 
referred  to,  are  often  found  either  intruding  themselves  in  amor- 
phous masses  and  dikes  into  the  old  fossiliferous  tilestones,  No.  4.,  or 
alternating  with  them  in  conformable  beds.  All  the  different 
divisions  of  the  red  sandstone,  1,  2,  3,  4,  are  occasionally  intersected 
by  dikes,  but  they  are  very  rare  in  Nos.  1.  and  2.,  the  upper 
members  of  the  group  consisting  of  red  shale  and  red  sandstone. 
These  phenomena,  which  occur  at  the  foot  of  the  Grampians,  are 
repeated  in  the  Sidlaw  Hills  ;  and  it  appears  that  in  this  part  of 
Scotland  volcanic  eruptions  were  most  frequent  in  the  earlier  part 
of  the  Old  Red  Sandstone  period. 

The  trap  rocks  alluded  to  consist  chiefly  of  felspathic  porphyry 
and  amygdaloid,  the  kernels  of  the  latter  being  sometimes  calca- 
reous, often  calcedonic,  and  forming  beautiful  agates.  We  meet 
also  with  claystone,  clinkstone,  greenstone,  compact  felspar,  and 
tuff.  Some  of  these  rocks  flowed  as  lavas  over  the  bottom  of  the 
sea,  and  enveloped  quartz  pebbles  which  were  lying  there,  so  as  to 
form  conglomerates  with  a  base  of  greenstone,  as  is  seen  in  Lumley 
Den,  in  the  Sidlaw  Hills.  On  either  side  of  the  axis  of  this  chain  of 
hills  (see  section,  p.  48.),  the  beds  of  massive  trap,  and  the  tuffs 
composed  of  volcanic  sand  and  ashes,  dip  regularly  to  the  south-east 
or  north-west,  conformably  with  the  shales  and  sandstones. 

Silurian  period.  —  It  appears  from  the  investigations  of  Sir  R. 
Murchison  in  Shropshire,  that  when  the  lower  Silurian  strata  of 
that  country  were  accumulating,  there  were  frequent  volcanic 
eruptions  beneath  the  sea ;  and  the  ashes  and  scorias  then  ejected 
gave  rise  to  a  peculiar  kind  of  tufaceous  sandstone  or  grit,  dissimilar 
to  the  other  rocks  of  the  Silurian  series,  and  only  observable  in 
places  where  syenitic  and  other  trap  rocks  protrude.  These  tuffs 
occur  on  the  flanks  of  the  Wrekin  and  Caer  Caradoc,  and  contain 

oo  2 


564  CAMBRIAN   VOLCANIC   ROCKS.  [Cn.  XXXII. 

Silurian  fossils,  such  as  casts  of  encrinites,  trilobites,  and  mollusca. 
Although  fossiliferous,  the  stone  resembles  a  sandy  claystone  of  the 
trap  family.* 

Thin  layers  of  trap,  only  a  few  inches  thick,  alternate,  in  some 
parts  of  Shropshire  and  Montgomeryshire,  with  a  sedimentary  strata 
of  the  lower  Silurian  system.  This  trap  consists  of  slaty  porphyry 
and  granular  felspar  rock,  the  beds  being  traversed  by  joints  like 
those  in  the  associated  sandstone,  limestone,  and  shale,  and  having 
the  same  strike  and  dip.f 

In  Radnorshire  there  is  an  example  of  twelve  bands  of  stratified 
trap,  alternating  with  Silurian  schists  and  flagstones,  in  a  thickness 
of  350  feet.  The  bedded  traps  consist  of  felspar-porphyry,  clink- 
stone, and  other  varieties ;  and  the  interposed  Llandeilo  flags  are  of 
sandstone  and  shale,  with  trilobites  and  graptolites.f 

Cambrian  Volcanic  Rocks.  —  In  a  former  chapter  (Ch.  XXVII. 
p.  451.),  we  have  seen  that  below  the  Llandeilo  and  Bala  beds  of 
Lower  Silurian  date  there  occur,  in  North  Wales,  a  series  of  rocks 
of  vast  thickness,  which  may  be  called  Cambrian.  The  upper 
subdivision,  named  by  Professor  Sedgwick  the  "  Festiniog  group," 
comprises,  first,  the  Arenig  Slates,  7000  feet  thick  in  North  Wales, 
in  the  midst  of  which  dense  masses  of  porphyry,  trap-conglomerate, 
and  other  igneous  rocks,  which  are  supposed  by  Professor  Sedgwick 
to  be  of  contemporaneous  origin,  are  intercalated ;  secondly,  the 
Lingula  flags  underlying  the  former,  and  of  which  the  fossils  were 
treated  of  at  p.  452. ;  thirdly,  still  lower,  the  Bangor  group  or 
Lower  Cambrian,  in  which  bands  of  felspathic  porphyry  occur. 
These  last  are,  in  the  opinion  of  Professor  Ramsay,  intrusive  and 
not  of  the  same  date  as  the  associated  sedimentary  deposits. 

Professor  Sedgwick  has  also  described,  in  his  account  of  the 
geology  of  Cumberland,  various  trap  rocks  which  accompany  green 
slates,  agreeing  in  mineral  character  and  aspect  with  the  Arenig 
Slates,  which  underlie  all  the  fossiliferous  strata  of  Cumberland,  and 
consist  of  felspathic  and  porphyritic  rocks  and  greenstones,  oc- 
curring not  only  in  dikes,  but  in  conformable  beds.  Occasionally 
there  is  a  passage  from  these  igneous  rocks  to  some  of  the  green 
quartzose  slates.  These  porphyries  are  supposed  to  have  been  pro- 
duced contemporaneously  with  the  stratified  chloritic  slates  by  sub- 
marine eruptions  oftentimes  repeated,  the  materials  of  the  slates 
having  been  supplied,  in  part  at  least,  from  the  same  source.  § 

*  Murchison,    Silurian   System,   &c.         J  Ibid.,  p.  325. 

p.  230.  §  Geol.  Trans.,    2d  series,  vol.   IT. 

f  Ibid.,  p.  272.  p.  55. 


CH.XXXITI.]  PLUTONIC    EOCKS.  565 


CHAPTER  XXXHI. 

PLUTONIC  ROCKS GRANITE. 

General  aspect  of  granite — Decomposing  into  spherical  masses  —  Rude  columnar 
structure — Analogy  and  difference  of  volcanic  and  plutonic  formations — Minerals 
in  granite,  and  their  arrangement  —  Graphic  and  porphyritic  granite — Mutual 
penetration  of  crystals  of  quartz  and  felspar  —  Occasional  minerals — Syenite  — 
Syenitic,  talcose,  and  schorly  granites — Eurite — Passage  of  granite  into  trap — 
Examples  near  Christiania  and  in  Aberdeenshire  —  Analogy  in  composition  of 
trachyte  and  granite  —  Granite  veins  in  Glen  Tilt,  Cornwall,  the  Valorsine,  and 
other  countries — Different  composition  of  veins  from  main  hody  of  granite  — 
Metalliferous  veins  in  strata  near  their  junction  with  granite — Apparent  isolation 
of  nodules  of  granite  —  Quartz  veins  —  Whether  plutonic  rocks  are  ever  over- 
lying —  Their  exposure  at  the  surface  due  to  denudation. 

THE  plutonic  rocks  may  be  treated  of  next  in  order,  as  they  are 
most  nearly  allied  to  the  volcanic  class  already  considered.  I  have 
described,  in  the  first  chapter,  these  plutonic  rocks  as  the  unstra- 
tified  division  of  the  crystalline  or  hypogene  formations,  and  have 
stated  that  they  differ  from  the  volcanic  rocks,  not  only  by  their 
more  crystalline  texture,  but  also  by  the  absence  of  tuffs  and 
breccias,  which  are  the  products  of  eruptions  at  the  earth's  surface, 
or  beneath  seas  of  inconsiderable  depth.  They  differ  also  by  the 
absence  of  pores  or  cellular  cavities,  to  which  the  expansion  of  the 
entangled  gases  gives  rise  in  ordinary  lava.  From  these  and  other 
peculiarities  it  has  been  inferred,  that  the  granites  have  been  formed 
at  considerable  depths  in  the  earth,  and  have  cooled  and  crystallized 
slowly  under  great  pressure,  where  the  contained  gases  could  not 
expand.  The  volcanic  rocks,  on  the  contrary,  although  they  also 
have  risen  up  from  below,  have  cooled  from  a  melted  state  more 
rapidly  upon  or  near  the  surface.  From  this  hypothesis  of  the 
great  depth  at  which  the  granites  originated,  has  been  derived  the 
name  of  "  Plutonic  rocks."  The  beginner  will  easily  conceive  that 
the  influence  of  subterranean  heat  may  extend  downwards  from  the 
crater  of  every  active  volcano  to  a  great  depth  below,  perhaps 
several  miles  or  leagues,  and  the  effects  which  are  produced  deep  in 
the  bowels  of  the  earth  may,  or  rather  must,  be  distinct;  so  that 
volcanic  and  plutonic  rocks,  each  different  in  texture,  and  sometimes 
even  in  composition,  may  originate  simultaneously,  the  one  at  the 
surface,  the  other  far  beneath  it. 

By  some  writers,  all  the  rocks  now  under  consideration  have  been 
comprehended  under  the  name  of  granite,  which  is,  then,  understood 
to  embrace  a  large  family  of  crystalline  and  compound  rocks,  usually 

o  o  3 


566  GENERAL   ASPECT    OF    GRANITE.          [Cn.  XXXIII. 

found  underlying  all  other  formations  ;  whereas  we  have  seen  that 
trap  very  commonly  overlies  strata  of  different  ages.  Granite  often 
preserves  a  very  uniform  character  throughout  a  wide  range  of 
territory,  forming  hills  of  a  peculiar  rounded  form,  usually  clad  with 
a  scanty  vegetation.  The  surface  of  the  rock  is  for  the  most  part  in 
a  crumbling  state,  and  the  hills  are  often  surmounted  by  piles  of 
stones  like  the  remains  of  a  stratified  mass,  as  in  the  annexed  figure, 

Fig.  681. 


Mass  of  granite  near  the  Sharp  Tor,  Cornwall. 

and  sometimes  like  heaps  of  boulders,  for  which  they  have  been 
mistaken.  The  exterior  of  these  stones,  originally  quadrangular, 
acquires  a  rounded  form  by  the  action  of  air  and  water,  for  the 
edges  and  angles  waste  away  more  rapidly  than  the  sides.  A 
similar  spherical  structure  has  already  been  described  as  charac- 
teristic of  basalt  and  other  volcanic  formations,  and  it  must  be  re- 
ferred to  analogous  causes,  as  yet  but  imperfectly  understood. 

Although  it  is  the  general  peculiarity  of  granite  to  assume  no 
definite  shapes,  it  is  nevertheless  occasionally  subdivided  by  fissures, 
so  as  to  assume  a  cuboidal,  and  even  a  columnar,  structure,  Ex- 
amples of  these  appearances  may  be  seen  near  the  Land's  End,  in 
Cornwall.  (See  fig.  682.) 

The  plutonic  formations  also  agree  with  the  volcanic  in  having 
veins  or  ramifications  proceeding  from  central  masses  into  the  ad- 
joining rocks,  and  causing  alterations  in  these  last,  which  will  be 
presently  described.  They  also  resemble  trap  in  containing  no 
organic  remains ;  but  they  differ  in  being  more  uniform  in  texture, 
whole  mountain  masses  of  indefinite  extent  appearing  to  have  ori- 
ginated under  conditions  precisely  similar.  They  also  differ  in 
never  being  scoriaceous  or  amygdaloidal,  and  never  forming  a 
porphyry  with  an  uncrystalline  base,  or  alternating  with  tuffs.  Nor 
do  they  form  conglomerates,  although  there  is  sometimes  an  in- 
sensible passage  from  a  fine  to  a  coarse-grained  granite,  and  occa- 
sionally patches  of  a  fine  texture  are  imbedded  in  a  coarser  variety. 

Felspar,  quartz,  and  mica  are  usually  considered  as  the  minerals 
essential  to  granite,  the  felspar  being  most  abundant  in  quantity,  and 
the  proportion  of  quartz  exceeding  that  of  mica.  These  minerals 
are  united  in  what  is  termed  a  confused  crystallization  ;  that  is  to 
say,  there  is  no  regular  arrangement  of  the  crystals  in  granite,  as  in 
gneiss  (see  fig.  704.  p.  595.),  except  in  the  variety  termed  graphic 
granite,  which  occurs  mostly  in  granitic  veins.  This  variety  is  a 


CHfXXXIII.]      MINERAL   COMPOSITION    OF    GRANITE. 

Fig.  682. 


567 


Granite  having  a  cuboidal  and  rude  columnar  structure,  Land's  End,  Cornwall. 

compound  of  felspar  and  quartz,  so  arranged  as  to  produce  an 
imperfect  laminar  structure.  The  crystals  of  felspar  appear  to  have 
been  first  formed,  leaving  between  them  the  space  now  occupied  by 
the  darker- coloured  quartz.  This  mineral,  when  a  section  is  made 


Fig.  6^3. 


Fig.  <584. 


Graphic  granite. 

Fig.  683.  Section  parallel  to  the  lamina;. 
Fig.  684.  Section  transverse  to  the  laminae. 

at  right  angles  to  the  alternate  plates  of  felspar  and  quartz,  presents 
broken  lines,  which  have  been  compared  to  Hebrew  characters. 
The  variety  of  granite  called  by  the  French  Pegmatite,  which  is  a 
mixture  of  quartz  and  common  felspar,  usually  with  some  small 
admixture  of  white  silvery  mica,  often  passes  into  graphic  granite. 

As  a  general  rule,  quartz,  in  a  compact  or  amorphous  state,  forms 
a  vitreous  mass,  serving  as  the  base  in  which  felspar  and  mica  have 
crystallized  ;  for  although  these  minerals  are  much  more  fusible 
than  silex,  they  have  often  imprinted  their  shapes  upon  the  quartz. 
This  fact,  apparently  so  paradoxical,  has  given  rise  to  much  in- 
genious speculation.  We  should  naturally  have  anticipated  that, 

oo4 


568  PORPHYRITIC   GRANITE.  [Cn.  XXXIII. 

during  the  cooling  of  the  mass,  the  flinty  portion  would  be  the  first 
to  consolidate ;  and  that  the  different  varieties  of  felspar,  as  well  as 
garnets  and  tourmalines,  being  more  easily  liquefied  by  heat,  would 
be  the  last.  Precisely  the;  reverse  has  taken  place  in  the  passage  of 
most  granite  aggregates  from  a  fluid  to  a  solid  state,  crystals  of  the 
more  fusible  minerals  being  found  enveloped  in  hard,  transparent, 
glassy  quartz,  which  has  often  taken  very  faithful  casts  of  each,  so 
as  to  preserve  even  the  microscopically  minute  striations  on  the 
surface  of  prisms  of  tourmaline.  Various  explanations  of  this  phe- 
nomenon have  been  proposed  by  MM.  de  Beaumont,  Fournet,  and 
Durocher.  They  refer  to  M.  Guadin's  experiments  on  the  fusion 
of  quartz,  which  show  that  silex,  as  it  cools,  has  the  property  of 
remaining  in  a  viscous  state,  whereas  alumina  never  does.  This 
"gelatinous  flint"  is  supposed  to  retain  a  considerable  degree  of 
plasticity  long  after  the  granitic  mixture  has  acquired  a  low  tem- 
perature ;  and  M.  E.  de  Beaumont  suggests  that  electric  action  may 
prolong  the  duration  of  the  viscosity  of  silex.  Occasionally,  how- 
ever, we  find  the  quartz  and  felspar  mutually  imprinting  their  forms 
on  each  other,  affording  evidence  of  the  simultaneous  crystallization 
of  both.* 

It  may  here  be  remarked  that  ordinary  granite,  as  well  as  syenite 
and  eurite,  usually  contains  two  kinds  of  felspar,  1st,  the  common,  or 
orthoclase,  in  which  potash  is  the  prevailing  alkali,  and  this  generally 
occurs  in  large  crystals  of  a  white  or  flesh  colour  ;  and  2ndly,  felspar 
in  smaller  crystals,  in  which  soda  predominates,  usually  of  a  dead 
white  or  spotted,  and  striated  lake  albite,  but  not  the  same  in  com- 
position.f 

Porphyritic  granite.  —  This  name  has  been  sometimes  given  to 
that  variety  in  which  large  crystals  of  common  felspar,  sometimes 
more  than  3  inches  in  length,  are  scattered  through  an  ordinary  base 
of  granite.  An  example  of  this  texture  may  be  seen  in  the  granite 

Fig.  685. 


Porphyritic  granite.    Land's  End,  Cornwall. 

of  the  Land's  End,  in  Cornwall  (fig.  685.).    The  two  larger  prismatic 
crystals  in  this  drawing  represent  felspar,  smaller  crystals  of  which 

*  Bulletin,  2d  serie,  iv.   1304.  ;  and          f  Delesse,    Ann.    des   Mine?,    1852, 
Archiac,  Hist,  des  Progres  de  Geol.,  i.      t.  iii.  p.  409.,  and  1848.  t.  xiii.  p.  675. 
38. 


SYENITIC,  TALCOSE,  AND  SCHORL  GRANITES.    569 

are  also  seen,  similar  in  form,  scattered  through  the  base.  In  this 
base  also  appear  black  specks  of  mica,  the  crystals  of  which  have  a 
more  or  less  perfect  hexagonal  outline.  The  remainder  of  the  mass 
is  quartz,  the  translucency  of  which  is  strongly  contrasted  to  the 
opaqueness  of  the  white  felspar  and  black  mica.  But  neither  the 
transparency  of  the  quartz  nor  the  silvery  lustre  of  the  mica  can  be 
expressed  in  the  engraving. 

The  uniform  mineral  character  of  large  masses  of  granite  seems 
to  indicate  that  large  quantities  of  the  component  elements  were 
thoroughly  mixed  up  together,  and  then  crystallized  under  precisely 
similar  conditions.  There  are,  however,  many  accidental,  or  "  occa- 
sional," minerals,  as  they  are  termed,  which  belong  to  granite. 
Among  these  black  schorl  or  tourmaline,  actinolite,  zircon,  garnet, 
and  fluor  spar  are  not  uncommon ;  but  they  are  too  sparingly  dis- 
persed to  modify  the  general  aspect  of  the  rock.  They  show,  never- 
theless, that  the  ingredients  were  not  everywhere  exactly  the  same ; 
and  a  still  greater  variation  may  be  traced  in  the  ever-varying  pro- 
portions of  the  felspar,  quartz,  and  mica. 

Syenite.  —  When  hornblende  is  the  substitute  for  mica,  which  is 
very  commonly  the  case,  the  rock  becomes  Syenite :  so  called  from 
the  celebrated  ancient  quarries  of  Syene  in  Egypt.  It  has  all  the 
appearance  of  ordinary  granite,  except  when  mineralogically  ex- 
amined in  hand  specimens,  and  is  fully  entitled  to  rank  as  a  geo- 
logical member  of  the  same  plutonic  family  as  granite.  Syenite, 
however,  after  maintaining  the  granitic  character  throughout  ex- 
tensive regions,  is  not  uncommonly  found  to  lose  its  quartz,  and 
to  pass  insensibly  into  syenitic  greenstone,  a  rock  of  the  trap  family. 
Werner  considered  syenite  as  a  binary  compound  of  felspar  and 
hornblende,  and  regarded  quartz  as  merely  one  of  its  occasional 
minerals. 

Syenitic  granite.  —  The  quadruple  compound  of  quartz,  felspar, 
mica,  and  hornblende,  may  be  so  termed.  This  rock  occurs  in  Scot- 
land and  in  Guernsey. 

Talcose  granite,  or  Protogine  of  the  French,  is  a  mixture  of  fel- 
spar, quartz,  and  talc.  It  abounds  in  the  Alps,  and  in  some  parts  of 
Cornwall,  producing  by  its  decomposition  the  china  clay,  more  than 
12,000  tons  of  which  are  annually  exported  from  that  country  for 
the  potteries.* 

Schorl  rock,  and  schorly  granite.  —  The  former  of  these  is  an 
aggregate  of  schorl,  or  tourmaline,  and  quartz.  When  felspar  and 
mica  are  also  present,  it  may  be  called  schorly  granite.  This  kind  of 
granite  is  comparatively  rare. 

Eurite.  —  A  rock  in  which  all  the  ingredients  of  granite  are  blended 
into  a  finely  granular  mass.  When  crystalline,  it  is  seen  to  contain 
crystals  of  quartz,  mica,  common  felspar,  and  soda  felspar.  When 
there  is  no  irica,  and  when  common  felspar  predominates,  so 
as  to  give  it  a  white  colour,  it  becomes  a  felspathic  granite,  called 

*  Boase  on  Primary  Geology,  p.  16. 


570  PASSAGE    OF    GRANITE    INTO    TRAP.       [Cn.  XXXIII. 

'*  whitestone  "  (Weisstein)  by  Werner,  or  Leptynite  by  the  French, 
in  which  microscopic  crystals  of  garnet  are  often  present. 

All  these  and  other  varieties  of  granite  pass  into  certain  kinds  of 
trap,  a  circumstance  which  affords  one  of  many  arguments  in 
favour  of  what  is  now  the  prevailing  opinion,  that  the  granites  are 
also  of  igneous  origin.  The  contrast  of  the  most  crystalline  form  of 
granite  to  that  of  the  most  common  and  earthy  trap  is  undoubtedly 
great ;  but  each  member  of  the  volcanic  class  is  capable  of  becoming 
porphyritic,  and  the  base  of  the  porphyry  may  be  more  and  more 
crystalline,  until  the  mass  passes  to  the  kind  of  granite  most  nearly 
allied  in  mineral  composition. 

The  minerals  which  constitute  alike  the  granitic  and  volcanic 
rocks  consist,  almost  exclusively,  of  seven  elements,  namely,  silica, 
alumina,  magnesia,  lime,  soda,  potash,  and  iron  (see  Table,  p.  479.)  ; 
and  these  may  sometimes  exist  in  about  the  same  proportions  in  a 
porous  lava,  a  compact  trap,  or  a  crystalline  granite.  It  may  perhaps 
be  found,  on  farther  examination  —  for  on  this  subject  we  have  yet 
much  to  learn  —  that  the  presence  of  these  elements  in  certain  pro- 
portions is  more  favourable  than  in  others  to  their  assuming  a 
crystalline  or  true  granitic  structure ;  but  it  is  also  ascertained  by 
experiment,  that  the  same  materials  may,  under  different  circum- 
stances, form  very  different  rocks.  The  same  lava,  for  example, 
may  be  glassy,  or  scoriaceous,  or  stony,  or  porphyritic,  according  to 
the  more  or  less  rapid  rate  at  which  it  cools  ;  and  some  trachytes  and 
syenitic-greenstones  may  doubtless  form  granite  and  syenite,  if  the 
crystallization  take  place  slowly. 

It  has  also  been  suggested  that  the  peculiar  nature  and  structure 
of  granite  may  be  due  to  its  retaining  in  it  that  water  which  is  seen 
to  escape  from  lavas  when  they  cool  slowly,  and  consolidate  in  the 
atmosphere.  Boutigny's  experiments  have  shown  that  melted  matter, 
at  a  white  heat,  requires  to  have  its  temperature  lowered  before  it 
can  vapourize  water  ;  and  such  discoveries,  if  they  fail  to  explain  the 
manner  in  which  granites  have  been  formed,  serve  at  least  to  remind 
us  of  the  entire  distinctness  of  the  conditions  under  which  plutonic 
and  volcanic  rocks  must  be  produced.* 

It  would  be  easy  to  multiply  examples  and  authorities  to  prove 
the  gradation  of  the  granitic  into  the  trap  rocks.  On  the  western 
side  of  the  fiord  of  Christiania,  in  Norway,  there  is  a  large  district 
of  trap,  chiefly  greenstone-porphyry  and  syenitic-greenstone,  resting 
on  fossiliferous  strata.  To  this,  on  its  southern  limit,  succeeds  a 
region  equally  extensive  of  syenite,  the  passage  from  the  volcanic  to 
the  plutonic  rock  being  so  gradual  that  it  is  impossible  to  draw  a 
line  of  demarcation  between  them. 

"  The  ordinary  granite  of  Aberdeenshire,"  says  Dr.  MacCulloch, 
"  is  the  usual  ternary  compound  of  quartz,  felspar,  and  mica ;  but 
sometimes  hornblende  is  substituted  for  the  mica.  But  in  many 
places  a  variety  occurs  which  is  composed  simply  of  felspar  and 

*  E.  de  Beaumont,  Bulletin,  vol.  iv.,  2d  ser.,  pp.  1318.  and  1320. 


CH.  XXXIII.]      ROCKS   ALTERED   BY   GRANITE   VEINS. 


571 


hornblende;  and  in  examining  more  minutely  this  duplicate  com- 
pound, it  is  observed  in  some  places  to  assume  a  fine  grain,  and  at 
length  to  become  undistinguishable  from  the  greenstones  of  the  trap 
family.  It  also  passes  in  the  same  uninterrupted  manner  into  a 
basalt,  and  at  length  into  a  soft  claystone,  with  a  schistose  tendency 
on  exposure,  in  no  respect  differing  from  those  of  the  trap  islands  of 
the  western  coast."  The  same  author  mentions,  that  in  Shetland 
a  granite  composed  of  hornblende,  mica,  felspar,  and  quartz  graduates 
in  an  equally  perfect  manner  into  basalt.* 

In  Hungary  there  are  varieties  of  trachyte,  which,  geologically 
speaking,  are  of  modern  origin,  in  which  crystals,  not  only  of  mica, 
but  of  quartz,  are  common,  together  with  felspar  and  hornblende. 
It  is  easy  to  conceive  how  such  volcanic  masses  may,  at  a  certain 
depth  from  the  surface,  pass  downwards  into  granite. 

I  have  already  hinted  at  the  close  analogy  in  the  forms  of  certain 
granitic  and  trappean  veins ;  and  it  will  be  found  that  strata  pene- 
trated by  plutonic  rocks  have  suffered  changes  very  similar  to  those 
exhibited  near  the  contact  of  volcanic  dikes.  Thus,  in  Glen  Tilt,  in 
Scotland,  alternating  strata  of  limestone  and  argillaceous  schist  come 
in  contact  with  a  mass  of  granite.  The  contact  does  not  take  place 
as  might  have  been  looked  for,  if  the  granite  had  been  formed  there 
before  the  strata  were  deposited,  in  which  case  the  section  would 
have  appeared  as  in  fig.  686. ;  but  the  union  is  as  represented  in 


Fig.  686. 


Fig.  687. 


Junction  of  granite  and  argillaceous  schist  in  Glen 
Tilt    (Mac  Culloch.)t 

fig.  687.,  the  undulating  outline  of  the  granite  intersecting  different 
strata,  and  occasionally  intruding  itself  in  tortuous  veins  into  the 
beds  of  clay-slate  and  limestone,  from  which  it  differs  so  remarkably 
in  composition.  The  limestone  is  sometimes  changed  in  character 
by  the  proximity  of  the  granitic  mass  or  its  reins,  and  acquires  a 
more  compact  texture,  like  that  of  hornstone  or  chert,  with  a  splintery 
fracture,  and  effervescing  feebly  with  acids. 

The  annexed  diagram  (fig.  688.)  represents  another  junction,  in 
the  same  district,  where  the  granite  sends  forth  so  many  veins  as  to 
reticulate  the  limestone  and  schist,  the  veins  diminishing  towards 


*  Syst.  of   Geol.  vol.  i.  p.  157.  and 
158. 


t  Geol.   Trans.,   1st  series,  vol.  iii. 
pi.  21. 


572 


ROCKS   ALTERED    BY   GRANITE    VEINS.       [Cn.  XXXIII, 
Fig.  688. 


Junction  of  granite  and  limestone  in  Glen  Tilt.    (MacCulloch.) 

a.  Granite.  b.  Limestone. 

c.  Blue  argillaceous  schist. 

their  termination  to  the  thickness  of  a  leaf  of  paper  or  a  thread.  In 
some  places  fragments  of  granite  appear  entangled,  as  it  were,  in  the 
limestone,  and  are  not  visibly  connected  with  any  larger  mass  ; 
while  sometimes,  on  the  other  hand,  a  lump  of  the  limestone  is  found 
in  the  midst  of  the  granite.  The  ordinary  colour  of  the  limestone  of 
Glen  Tilt  is  lead  blue,  and  its  texture  large-grained  and  highly 
crystalline ;  but  where  it  approximates  to  the  granite,  particularly 
where  it  is  penetrated  by  the  smaller  veins,  the  crystalline  texture 
disappears,  and  it  assumes  an  appearance  exactly  resembling  that  of 
hornstone.  The  associated  argillaceous  schist  often  passes  into 
hornblende  slate,  where  it  approaches  very  near  to  the  granite.* 

The  conversion  of  the  limestone  in  these  and  many  other  in- 
stances into  a  siliceous  rock,  effervescing  slowly  with  acids,  would 
be  difficult  of  explanation,  were  it  not  ascertained  that  such  lime- 
stones are  always  impure,  containing  grains  of  quartz,  mica,  or 
felspar  disseminated  through  them.  The  elements  of  these  minerals, 
when  the  rock  has  been  subjected  to  great  heat,  may  have  been 
fused,  and  so  spread  more  uniformly  through  the  whole  mass. 

In  the  plutonic,  as  in  the  volcanic  rocks,  there  is  every  gradation 
from  a  tortuous  vein  to  the  most  regular  form  of  a  dike,  such  as 
intersect  the  tuffs  and  lavas  of  Vesuvius  and  Etna.  Dikes  of 
granite  may  be  seen,  among  other  places,  on  the  southern  flank  of 


»  MacCulloch.  Geol.  Trans.,  vol.  iii.  p.  259. 


CH.  XXXIII.]        STKUCTUKE   OF   GKANITE   VEINS.  573 

Mount  Battock,  one  of  the  Grampians,  the  opposite  walls  sometimes 
preserving  an  exact  parallelism  for  a  considerable  distance. 

As  a  general  rule,  however,  granite  veins  in  all  quarters  of  the 
globe  are  more  sinuous  in  their  course  than  those  of  trap.  They 
present  similar  shapes  at  the  most  northern  point  of  Scotland,  and 
the  southernmost  extremity  of  Africa,  as  the  annexed  drawings  will 
show. 


Fig.  689. 


Fig, 


Granite  veins  traversing  clay  slate,  Table 
Mountain,  Cape  of  Good  Hope.* 


Granite  veins  traversing  gneiss,  Cape  Wrath. 
(MacCulloch.)t 


It  is  not  uncommon  for  one  set  of  granite  veins  to  intersect 
another ;  and  sometimes  there  are  three  sets,  as  in  the  environs  of 
Heidelberg,  where  the  granite  on  the  banks  of  the  river  Necker  is 
seen  to  consist  of  three  varieties,  differing  in  colour,  grain,  and 
various  peculiarities  of  mineral  composition.  One  of  these,  which  is 
evidently  the  second  in  age,  is  seen  to  cut  through  an  older  granite ; 
and  another,  still  newer,  traverses  both  the  second  and  the  first. 

In  Shetland  there  are  two  kinds  of  granite.  One  of  them,  com- 
posed of  hornblende,  mica,  felspar,  and  quartz,  is  of  a  dark  colour, 
and  is  seen  underlying  gneiss.  The  other  is  a  red  granite,  which 
penetrates  the  dark  variety  everywhere  in  veins.J 

The  accompanying  sketches  will  explain  the  manner  in  which 
granite  veins  often  ramify  and  cut  each  other  (figs.  690.  and  691.). 
They  represent  the  manner  in  which  the  gneiss  at  Cape  Wrath,  in 
Sutherlandshire,  is  intersected  by  veins.  Their  light  colour,  strongly 
contrasted  with  that  of  the  hornblende-schist,  here  associated  with 
the  gneiss,  renders  them  very  conspicuous. 

Granite  very  generally  assumes  a  finer  grain,  and  undergoes  a 
change  in  mineral  composition,  in  the  veins  which  it  sends  into 
contiguous  rocks.  Thus,  according  to  Professor  Sedgwick,  the 
main  body  of  the  Cornish  granite  is  an  aggregate  of  mica,  quartz, 
and  felspar;  but  the  veins  are  sometimes  without  mica,  being  a 
granular  aggregate  of  quartz  and  felspar.  In  other  varieties  quartz 


*  Capt.  B.   Hall,   Trans.  Roy.  Soc. 
Edin.,  vol.  vii. 

f  Western  Islands,  pi.  31. 


J  MacCulloch,  Syst.  of  Geol.,  vol.  i 
p.  58. 


574 


MINERAL    STRUCTURE    OP 

Fig.  G91. 


[Cn.  XXXIII. 


Granite  veins  traversing  gneiss  at  Cape  Wrath,  in  Scotland.    (MacCulloch.) 

prevails  to  the  almost  entire  exclusion  both  of  felspar  and  mica ;  in 
others,  the  mica  and  quartz  both  disappear,  and  the  vein  is  simply 
composed  of  white  granular  felspar.* 

Fig.  692.  is  a  sketch  of  a  group  of  granite  veins  in  Cornwall, 
given  by  Messrs.  Von  Oeynhausen  and  Yon  Dechen.f     The  main 


Fig.  692. 


Granite  veins  passing  through  hornblende  slate,  Carnsilver  Cove,  Cornwall. 

body  of  the  granite  here  is  of  a  porphyritic  appearance,  with  large 
crystals  of  felspar ;  but  in  the  veins  it  is  fine-grained,  and  without 
these  large  crystals.  The  general  height  of  the  veins  is  from  16  to 
20  feet,  but  some  are  much  higher. 

In  the  Valorsine,  a  valley  not  far  from  Mont  Blanc  in  Swit- 
zerland, an  ordinary  granite,  consisting  of  felspar,  quartz,  and  mica, 
sends  forth  veins  into  a  talcose  gneiss  (or  stratified  protogine),  and 
in  some  places  lateral  ramifications  are  thrown  off  from  the  principal 
veins  at  right  angles  (see  fig.  693.),  the  veins,  especially  the  minute 
ones,  being  finer  grained  than  the  granite  in  mass. 

It  is  here  remarked,  that  the  schist  and  granite,  as  they  approach, 
seem  to  exercise  a  reciprocal  influence  on  each  other,  for  both 


*  On  GeoL  of  Cornwall,  Camb.  Trans. 
vol.i.  p.  124. 


f  Phil.  Mag.   and   Annals,  No.  27. 
new  series,  March,  1829. 


GRANITE   IN   VEINS. 

Fig.  693. 


575 


Veins  of  granite  in  talcose  gneiss.    (L.  A.  Necker.) 

undergo  a  modification  of  mineral  character.  The  granite,  still 
remaining  unstratified,  becomes  charged  with  green  particles ;  and 
the  talcose  gneiss  assumes  a  granitiform  structure  without  losing  its 
stratification.* 

Professor  Keilhau  drew  my  attention  to  several  localities  in  the 
country  near  Christiania,  where  the  mineral  character  of  gneiss 
appears  to  have  been  affected  by  a  granite  of  much  newer  origin, 
for  some  distance  from  the  point  of  contact.  The  gneiss,  without 
losing  its  laminated  structure,  seems  to  have  become  charged  with  a 
larger  quantity  of  felspar,  and  that  of  a  redder  colour,  than  the 
felspar  usually  belonging  to  the  gneiss  of  Norway. 

Granite,  syenite,  and  those  porphyries  which  have  a  granitiform 
structure,  in  short  all  plutonic  rocks,  are  frequently  observed  to 
contain  metals,  at  or  near  their  junction  with  stratified  formations. 
On  the  other  hand,  the  veins  which  traverse  stratified  rocks  are,  as 
a  general  law,  more  metalliferous  near  such  junctions  than  in  other 
positions.  Hence  it  has  been  inferred  that  these  metals  may  have 
been  spread  in  a  gaseous  form  through  the  fused  mass,  and  that  the 
contact  of  another  rock,  in  a  different  state  of  temperature,  or  some- 
times the  existence  of  rents  in  other  rocks  in  the  vicinity,  may  have 
caused  the  sublimation  of  the  metals.']' 

There  are  many  instances,  as  at  Markerud,  near  Christiania,  in 
Norway,  where  the  strike  of  the  beds  has  not  been  deranged 
throughout  a  large  area  by  the  intrusion  of  granite,  both  in  large 
masses  and  in  veins.  This  fact  is  considered  by  some  geologists  to 
militate  against  the  theory  of  the  forcible  injection  of  granite  in  a 
fluid  state.  But  it  may  be  stated  in  reply,  that  ramifying  dikes  of 
trap  also,  which  almost  all  now  admit  to  have  been  once  fluid,  pass 
through  the  same  fossiliferous  strata,  near  Christiania,  without 
deranging  their  strike  or  dip.  J 

The  real  or  apparent  isolation  of  large  or  small  masses  of  granite 
detached  from  the  main  body,  as  at  a,  b,  fig.  694.,  and  above,  fig. 
688.,  and  «,  fig.  693.,  has  been  thought  by  some  writers  to  be  irre- 


*  Necker,  sur  la  Val.  de  Valorsine, 
Mem.  de  la  Soc.  de  Phys.  de  Geneve, 
1828.  I  visited,  in  1832,  the  spot  re- 
ferred to  in  fig.  693. 


f  Necker,  Proceedings  of  Geol.  Soc. 
No.  26.  p.  392. 

%  See  Keilhau's  Gaea  Norvegica ; 
Christiania,  1838. 


576 


QUARTZ   VEINS. 

Fig.  694. 


[Cn.  XXXIII. 


General  view  of  junction  of  granite  and  schist  of  the  Valorsine. 
(L.  A.  Necker.) 

concilable  with  the  doctrine  usually  taught  respecting  veins;  but 
many  of  them  may,  in  fact,  be  sections  of  root-shaped  prolongations 
of  granite ;  while,  in  other  cases,  they  may  in  reality  be  detached 
portions  of  rock  having  the  plutonic  structure.  For  there  may 
have  been  spots  in  the  midst  of  the  invaded  strata,  in  which  there 
was  an  assemblage  of  materials  more  fusible  than  the  rest,  or  more 
fitted  to  combine  readily  into  some  form  of  granite. 

Veins  of  pure  quartz  are  often  found  in  granite  as  in  many 
stratified  rocks,  but  they  are  not  traceable,  like  veins  of  granite  or 
trap,  to  large  bodies  of  rock  of  similar  composition.  They  appear 
to  have  been  cracks,  into  which  siliceous  matter  was  infiltered. 
Such  segregation,  as  it  is  called,  can  sometimes  be  shown  to  have 
clearly  taken  place  long  subsequently  to  the  original  consolidation 
of  the  containing  rock.  Thus,  for  example,  I  observed  in  the 
gneiss  of  Tronstad  Strand,  near  Drammen,  in  Norway,  the  annexed 
section  on  the  beach.  It  appears  that  the  alternating  strata  of 
whitish  granitiform  gneiss  and  black  hornblende-schist  were  first  cut 

through  by  a  greenstone  dike, 
about  2J  feet  wide ;  then  the 
crack  a  b  passed  through  all 
these  rocks,  and  was  filled  up 
with  quartz.  The  opposite 
walls  of  the  vein  are  in  some 
parts  incrusted  with  trans- 
parent crystals  of  quartz,  the 
middle  of  the  vein  being  filled 
up  with  common  opaque  white 
quartz. 

We  have  seen  that  the  vol- 
canic formations  have  been 
called  overlying,  because  they  not  only  penetrate  others  but  spread 
over  them.  Mr.  Necker  has  proposed  to  call  the  granites  the 
underlying  igneous  rocks,  and  the  distinction  here  indicated  is 
highly  characteristic.  It  was  indeed  supposed  by  some  of  the 
earlier  observers,  that  the  granite  of  Christiania,  in  Norway,  was 
intercalated  in  mountain  masses  between  the  primary  or  paleozoic 
strata  of  that  country,  so  as  to  overlie  fossiliferous  shale  and  lime- 


Fig.  695. 


Gneiss. 


Gneiss. 


a,  b.  Quartz  vein  passing  through  gneiss  and  green- 
stone, Tronstad  Strand,  near  Chrisiiauia. 


Cn.'XXXIII.]  CONFORMABLE   PORPHYRIES. 


577 


stone.  But  although  the  granite  sends  veins  into  these  fossiliferous 
rocks,  and  is  decidedly  posterior  in  origin,  its  actual  superposition 
in  mass  has  been  disproved  by  Professor  Keilhau,  whose  obser- 
vations on  this  controverted  point  I  had  opportunities  in  1837  of 
verifying.  There  are,  however,  on  a  smaller  scale,  certain  beds  of 
euritic  porphyry,  some  a  few  feet,  others  many  yards  in  thickness, 
which  pass  into  granite,  and  deserve  perhaps  to  be  classed  as 
plutonic  rather  than  trappean  rocks,  which  may  truly  be  described 
as  interposed  conformably  between  fossiliferous  strata,  as  the  por- 
phyries (a,  c,  fig.  696.),  which  divide  the  bituminous  shales  and 


Euritic  porphyry  alternating  with  primary  fossiliferous  strata, 
near  Christiania. 

argillaceous  limestones,  ff.  But  some  of  these  same  porphyries  are 
partially  unconformable,  as  b,  and  may  lead  us  to  suspect  that  the 
others  also,  notwithstanding  their  appearance  of  interstratification, 
have  been  forcibly  injected.  Some  of  the  porphyritic  rocks  above 
mentioned  are  highly  quartzose,  others  very  felspathic.  In  pro- 
portion as  the  masses  are  more  voluminous,  they  become  more 
granitic  in  their  texture,  less  conformable,  and  even  begin  to  send 
forth  veins  into  contiguous  strata.  In  a  word,  we  have  here  a 
beautiful  illustration  of  the  intermediate  gradations  between  volcanic 
and  plutonic  rocks,  not  only  in  their  mineralogical  composition  and 
structure,  but  also  in  their  relations  of  position  to  associated  form- 
ations. If  the  term  overlying  can  in  this  instance  be  applied  to  a 
plutonic  rock,  it  is  only  in  proportion  as  that  rock  begins  to  acquire 
a  trappean  aspect. 

It  has  been  already  hinted  that  the  heat,  which  in  every  active 
volcano  extends  downwards  to  indefinite  depths,  must  produce 
simultaneously  very  different  |feffects  near  the  surface  and  far  below 
it;  and  we  cannot  suppose  that  rocks  resulting  from  the  crystal- 
lizing of  fused  matter  under  a  pressure  of  several  thousand  feet, 
much  less  miles,  of  the  earth's  crust  can  resemble  those  formed  at  or 
near  the  surface.  Hence  the  production  at  great  depths  of  a  class 
of  rocks  analogous  to  the  volcanic,  and  yet  differing  in  many  par- 
ticulars, might  also  have  been  predicted,  even  had  we  no  plutonic 
formations  to  account  for.  How  well  these  agree,  both  in  their 
positive  and  negative  characters,  with  the  theory  of  their  deep 
subterranean  origin,  the  student  will  be  able  to  judge  by  considering 
the  descriptions  already  given. 

It  has,  however,  been  objected,  that  if  the  granitic  and  volcanic 
rocks  were  simply  different  parts  of  one  great  series,  we  ought  to 
find  in  mountain  chains  volcanic  dikes  passing  upwards  into  lava 

PP 


578  GRANITIC  ROCKS.  [Cn.  XXXIII. 

and  downwards  into  granite.  But  we  may  answer  that  our  vertical 
sections  are  usually  of  small  extent ;  and  if  we  find  in  certain  places 
a  transition  from  trap  to  porous  lava,  and  in  others  a  passage  from 
granite  to  trap,  it  is  as  much  as  could  be  expected  of  this  evidence. 

The  prodigious  extent  of  denudation  which  has  been  already  de- 
monstrated to  have  occurred  at  former  periods,  will  reconcile  the 
student  to  the  belief  that  crystalline  rocks  of  high  antiquity,  al- 
though deep  in  the  earth's  crust  when  originally  formed,  may  have 
become  uncovered  and  exposed  at  the  surface.  Their  actual  ele- 
vation above  the  sea  may  be  referred  to  the  same  causes  to  which 
we  have  attributed  the  upheaval  of  marine  strata,  even  to  the 
summits  of  some  mountain  chains.  But  to  these  and  other  topics,  I 
shall  revert  when  speaking,  in  the  next  chapter,  of  the  relative  ages 
of  different  masses  of  granite. 


CnrXXXIV.]      TESTS   OF   AGE   OF  PLUTONIC   HOCKS.  579 


CHAPTER  XXXIV. 

ON  THE  DIFFERENT  AGES  OF  THE  PLUTONIC  ROCKS. 

Difficulty  in  ascertaining  the  precise  age  of  a  plutonic  rock — Test  of  age  by  relative 
position — Test  by  intrusion  and  alteration — Test  by  mineral  composition  — 
Test  by  included  fragments — Kecent  and  Pliocene  plutonic  rocks,  why  invisible 
— Tertiary  plutonic  rocks  in  the  Andes — Granite  altering  Cretaceous  rocks  — 
Granite  altering  Lias  in  the  Alps  and  in  Skye  —  Granite  of  Dartmoor  altering 
Carboniferous  strata  —  Granite  of  the  Old  Red  Sandstone  period  —  Syenite 
altering  Silurian  strata  in  Norway — Blending  of  the  same  with  gneiss  —  Most 
ancient  plutonic  rocks — Granite  protruded  in  a  solid  form — On  the  probable  age 
of  the  granites  of  Arran,  in  Scotland. 

WHEN  we  adopt  the  igneous  theory  of  granite,  as  explained  in  the 
last  chapter,  and  believe  that  different  plutonic  rocks  have  originated 
at  successive  periods  beneath  the  surface  of  the  planet,  we  must  be 
prepared  to  encounter  greater  difficulty  in  ascertaining  the  precise 
age  of  such  rocks,  than  in  the  case  of  volcanic  and  fossiliferous  form- 
ations. We  must  bear  in  mind,  that  the  evidence  of  the  age  of 
each  contemporaneous  volcanic  rock  was  derived,  either  from  lavas 
poured  out  upon  the  ancient  surface,  whether  in  the  sea  or  in  the 
atmosphere,  or  from  tuffs  and  conglomerates,  also  deposited  at  the 
surface,  and  either  containing  organic  remains  themselves,  or  inter- 
calated between  strata  containing  fossils.  But  all  these  tests  fail 
when  we  endeavour  to  fix  the  chronology  of  a  rock  which  has  crys- 
tallized from  a  state  of  fusion  in  the  bowels  of  the  earth.  In  that 
case,  we  are  reduced  to  the  following  tests :  1st,  relative  position ; 
2dly,  intrusion,  and  alteration  of  the  rocks  in  contact ;  3dly,  mineral 
characters ;  4thly,  included  fragments. 

Test  of  age  by  relative  position.  —  Unaltered  fossiliferous  strata  of 
every  age  are  met  with  reposing  immediately  on  plutonic  rocks ;  as 
at  Christiania,  in  Norway,  where  the  Newer  Pliocene  deposits  rest 
on  granite  ;  in  Auvergne,  where  the  freshwater  Eocene  strata,  and 
at  Heidelberg,  on  the  Rhine,  where  the  New  Red  sandstone  occupy 
a  similar  place.  In  all  these,  and  similar  instances,  inferiority  in 
position  is  connected  with  the  superior  antiquity  of  granite.  The 
crystalline  rock  was  solid  before  the  sedimentary  beds  were  super- 
imposed, and  the  latter  usually  contain  in  them  rounded  pebbles  of 
the  subjacent  granite. 

Test  by  intrusion  and  alteration. — But  when  plutonic  rocks  send 
veins  into  strata,  and  alter  them  near  the  point  of  contact,  in  the 
manner  before  described  (p.  571.),  it  is  clear  that,  like  intrusive 
traps,  they  are  newer  than  the  strata  which  they  invade  and  alter. 
Examples  of  the  application  of  this  test  will  be  given  in  the  sequel. 

PP  2 


580  RECENT   AND   PLIOCENE  [Cn.  XXXIV. 

Test  by  mineral  composition. — Notwithstanding  a  general  uni- 
formity in  the  aspect  of  plutonic  rocks,  we  have  seen  in  the  last  chap- 
ter that  there  are  many  varieties,  such  as  Syenite,  Talcose  granite, 
and  others.  One  of  these  varieties  is  sometimes  found  exclusively 
prevailing  throughout  an  extensive  region,  where  it  preserves  a 
homogeneous  character ;  so  that,  having  ascertained  its  relative  age 
in  one  place,  we  can  easily  recognize  its  identity  in  others,  and  thus 
determine  from  a  single  section  the  chronological  relations  of  large 
mountain  masses.  Having  observed,  for  example,  that  the  syenitic 
granite  of  Norway,  in  which  the  mineral  called  zircon  abounds,  has 
altered  the  Silurian  strata  wherever  it  is  in  contact,  we  do  not 
hesitate  to  refer  other  masses  of  the  same  zircon-syenite  in  the  south 
of  Norway  to  the  same  era. 

Some  have  imagined  that  the  age  of  different  granites  might,  to  a 
great  extent,  be  determined  by  their  mineral  characters  alone ;  syenite, 
for  instance,  or  granite  with  hornblende,  being  more  modern  than 
common  or  micaceous  granite.  But  modern  investigations  have  proved 
these  generalizations  to  have  been  premature.  The  syenitic  granite 
of  Norway  already  alluded  to  may  be  of  the  same  age  as  the  Silurian 
strata,  which  it  traverses  and  alters,  or  may  belong  to  the  Old  Red 
sandstone  period ;  whereas  the  granite  of  Dartmoor,  although  con- 
sisting of  mica,  quartz,  and  felspar,  is  newer  than  the  coal.  (See 
p.  586.)- 

Test  by  included  fragments.  —  This  criterion  can  rarely  be  of  much 
importance,  because  the  fragments  involved  in  granite  are  usually  so 
much  altered,  that  they  cannot  be  referred  with  certainty  to  the  rocks 
whence  they  were  derived.  In  the  White  Mountains,  in  North 
America,  according  to  Professor  Hubbard,  a  granite  vein,  traversing 
granite,  contains  fragments  of  slate  and  trap  which  must  have  fallen 
into  the  fissure  when  the  fused  materials  of  the  vein  were  injected 
from  below  *,  and  thus  the  granite  is  shown  to  be  newer  than  certain 
superficial  slaty  and  trappean  formations. 

Recent  and  Pliocene  plutonic  rocks,  why  invisible.  —  The  explana- 
tions already  given  in  the  29th  and  in  the  last  chapter  of  the  probable 
relation  of  the  plutonic  to  the  volcanic  formations,  will  naturally  lead 
the  reader  to  infer,  that  rocks  of  the  one  class  can  never  be  produced 
at  or  near  the  surface  without  -some  members  of  the  other  being 
formed  below  simultaneously,  or  soon  afterwards.  It  is  not  uncom- 
mon for  lava-streams  to  require  more  than  ten  years  to  cool  in  the 
open  air  ;  and  where  they  are  of  great  depth,  a  much  longer  period. 
The  melted  matter  poured  from  Jorullo,  in  Mexico,  in  the  year  1759, 
which  accumulated  in  some  places  to  the  height  of  550  feet,  was 
found  to  retain  a  high  temperature  half  a  century  after  the  eruption.f 
We  may  conceive,  therefore,  that  great  masses  of  subterranean  lava 
may  remain  in  a  red-hot  or  incandescent  state  in  the  volcanic  foci 
for  immense  periods,  and  the  process  of  refrigeration  may  be  ex- 
tremely gradual.  Sometimes,  indeed,  this  process  may  be  retarded 

*  Silliman's  Journ.,  No.  69.  p.  123.  f  See  "Principles,"  Index,  " Jorullo," 


CH.  XXXIV.]  PLUTONIC   ROCKS.  581 

for  an  indefinite  period,  by  the  accession  of  fresh  supplies  of  heat ; 
for  we  find  that  the  lava  in  the  crater  of  Stromboli,  one  of  the  Lipari 
Islands,  has  been  in  a  state  of  constant  ebullition  for  the  last  two 
thousand  years ;  and  we  may  suppose  this  fluid  mass  to  communicate 
with  some  caldron  or  reservoir  of  fused  matter  below.  In  the  Isle 
of  Bourbon,  also,  where  there  has  been  an  emission  of  lava  once  in 
every  two  years  for  a  long  period,  the  lava  below  can  scarcely  fail  to 
have  been  permanently  in  a  state  of  liquefaction.  If  then  it  be  a 
reasonable  conjecture,  that  about  2000  volcanic  eruptions  occur  in 
the  course  of  every  century,  either  above  the  waters  of  the  sea  or 
beneath  them  *,  it  will  follow,  that  the  quantity  of  plutonic  rock 
generated,  or  in  progress  during  the  Recent  epoch,  must  already  have 
been  considerable. 

But  as  the  plutonic  rocks  originate  at  some  depth  in  the  earth's 
crust,  they  can  only  be  rendered  accessible  to  human  observation,  by 
subsequent  upheaval  and  denudation.  Between  the  period  when  a 
plutonic  rock  crystallizes  in  the  subterranean  regions  and  the  era  of 
its  protrusion  at  any  single  point  of  the  surface,  one  or  two  geological 
periods  must  usually  intervene.  Hence,  we  must  not  expect  to  find 
the  Recent  or  Newer  Pliocene  granites  laid  open  to  view,  unless  we 
are  prepared  to  assume  that  sufficient  time  has  elapsed  since  the 
commencement  of  the  Newer  Pliocene  period  for  great  upheaval  and 
denudation.  A  plutonic  rock,  therefore,  must,  in  general,  be  of  con- 
siderable antiquity  relatively  to  the  fossiliferous  and  volcanic  forma- 
tions, before  it  becomes  extensively  visible.  As  we  know  that  the 
upheaval  of  land  has  been  sometimes  accompanied  in  South  America 
by  volcanic  eruptions  and  the  emission  of  lava,  we  may  conceive  the 
more  ancient  plutonic  rocks  to  be  forced  upwards  to  the  surface  by 
the  newer  rocks  of  the  same  class  formed  successively  below,  —  sub- 
terposition  in  the  plutonic,  like  superposition  in  the  sedimentary 
rocks,  being  usually  characteristic  of  a  newer  origin. 

In  the  accompanying  diagram  (fig.  697.),  an  attempt  is  made  to 
show  the  inverted  order  in  which  sedimentary  and  plutonic  forma- 
tions may  occur  in  the  earth's  crust. 

The  oldest  plutonic  rock,  No.  I.,  has  been  upheaved  at  successive 
periods  until  it  has  become  exposed  to  view  in  a  mountain-chain. 
This  protrusion  of  No.  I.  has  been  caused  by  the  igneous  agency 
which  produced  the  newer  plutonic  rocks  Nos.  II.  in.  and  IV. 
Part  of  the  primary  fossiliferous  strata,  No.  1.,  have  also  been  raised 
to  the  surface  by  the  same  gradual  process.  It  will  be  observed  that 
the  Recent  strata  No.  4.  and  the  Recent  granite  or  plutonic  rock 
No.  IV.  are  the  most  remote  from  each  other  in  position,  although 
of  contemporaneous  date.  According  to  this  hypothesis,  the  con- 
vulsions of  many  periods  will  be  required  before  Recent  granite,  or 
granite  of  the  human  period,  will  be  upraised  so  as  to  form  the 
highest  ridges  and  central  axes  of  mountain-chains.  During  that 

*  "  Principles,"  Index,  "  Volcanic  Eruptions." 
'     PP  3 


582 


PLUTONIC   KOCKS. 


[Cn.  XXXIV, 


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CH.  XXXIV.]      "  PLUTONIC   ROCKS  IN   THE   ANDES.  583 

time  the  Recent  strata  No.  4.  might  be  covered  by  a  great  many 
newer  sedimentary  formations. 

Eocene  granite  and  plutonic  rocks.  —  In  a  former  part  of  this 
volume  (p.  231.),  the  great  nummulitic  formation  of  the  Alps  and 
Pyrenees  was  referred  to  the  Eocene  period,  and  it  follows  that  those 
vast  movements  which  have  raised  fossiliferous  rocks  from  the  level 
of  the  sea  to  the  height  of  more  than  10,000  feet  above  its  level 
have  taken  place  since  the  commencement  of  the  tertiary  epoch. 
Here,  therefore,  if  anywhere,  we  might  expect  to  find  hypogene 
formations  of  Eocene  date  breaking  out  in  the  central  axis  or  most 
disturbed  region  of  the  loftiest  chain  in  Europe.  Accordingly,  in 
the  Swiss  Alps,  even  i\\Qflysch,  or  upper  portion  of  the  nummulitic 
series,  has  been  occasionally  invaded  by  plutonic  rocks,  and  converted 
into  crystalline  schists  of  the  hypogene  class.  There  can  be  little 
doubt  that  even  the  talcose  granite  or  gneiss  of  Mont  Blanc  itself  has 
been  in  a  fused  or  pasty  state  since  iheflysch  was  deposited  at  the 
bottom  of  the  sea ;  and  the  question  as  to  its  age  is  not  so  much 
whether  it  be  a  secondary  or  tertiary  granite  or  gneiss,  as  whether  it 
should  be  assigned  to  the  Eocene  or  Miocene  epoch. 

Great  upheaving  movements  have  been  experienced  in  the  region 
of  the  Andes,  during  the  Post-Pliocene  period.  In  some  part,  there- 
fore, of  this  chain,  we  may  expect  to  discover  tertiary  plutonic  rocks 
laid  open  to  view.  What  we  already  know  of  the  structure  of  the 
Chilian  Andes  seems  to  realize  this  expectation.  In  a  transverse 
section,  examined  by  Mr.  Darwin,  between  Valparaiso  and  Mendoza, 
the  Cordillera  was  found  to  consist  of  two  separate  and  parallel 
chains,  formed  of  sedimentary  rocks  of  different  ages,  the  strata  in 
both  resting  on  plutpnic  rocks,  by  which  they  have  been  altered. 
In  the  western  or  oldest  range,  called  the  Peuquenes,  are  black  cal- 
careous clay-slates,  rising  to  the  height  of  nearly  14,000  feet  above 
the  sea,  in  which  are  shells  of  the  genera  Gryphtea,  Turritella,  Te- 
rebratula,  and  Ammonite.  These  rocks  are  supposed  to  be  of  the 
age  of  the  central  parts  of  the  secondary  series  of  Europe.  They 
are  penetrated  and  altered  by  dikes  and  mountain  masses  of  a  plu- 
tonic rock,  which  has  the  texture  of  ordinary  granite,  but  rarely 
contains  quartz,  being  a  compound  of  albite  and  hornblende. 

The  second  or  eastern  chain  consists  chiefly  of  sandstones  and 
conglomerates,  of  vast  thickness,  the  materials  of  which  are  derived 
from  the  ruins  of  the  western  chain.  The  pebbles  of  the  conglome- 
rates are,  for  the  most  part,  rounded  fragments  of  the  fossiliferous 
slates  before  mentioned.  The  resemblance  of  the  whole  series  to 
certain  tertiary  deposits  on'  the  shores  of  the  Pacific,  not  only  in 
mineral  character,  but  in  the  imbedded  lignite  and  silicified  woods, 
leads  to  the  conjecture  that  they  also  are  tertiary.  Yet  these  strata 
are  not  only  associated  with  trap  rocks  and  volcanic  tuffs,  but  are  also 
altered  by  a  granite  consisting  of  quartz,  felspar,  and  talc.  They  are 
traversed,  moreover,  by  dikes  of  the  same  granite,  and  by  numerous 
veins  of  iron,  copper,  arsenic,  silver,  and  gold ;  all  of  which  can  be 

pp  4 


584     VOLUME  OF  HIDDEN  PLUTONIC  ROCKS.  [Cn.  XXXIV. 

traced  to  the  underlying  granite.*  We  have,  therefore,  strong 
ground  to  presume  that  the  plutonic  rock  here  exposed  on  a  large 
scale  in  the  Chilian  Andes  is  of  later  date  than  certain  tertiary 
formations. 

But  the  theory  adopted  in  this  work  of  the  subterranean  origin  of 
the  hypogene  formations  would  be  untenable,  if  the  supposed  fact 
here  alluded  to,  of  the  appearance  of  tertiary  granite  at  the  surface 
was  not  a  rare  exception  to  the  general  rule.  A  considerable  lapse 
of  time  must  intervene  between  the  formation  of  plutonic  and  meta- 
morphic  rocks  in  the  nether  regions,  and  their  emergence  at  the  sur- 
face. For  a  long  series  of  subterranean  movements  must  occur 
before  such  rocks  can  be  uplifted  into  the  atmosphere  or  the  ocean ; 
and,  before  they  can  be  rendered  visible  to  man,  some  strata  which 
previously  covered  them  must  usually  have  been  stripped  off  by  de- 
nudation. 

We  know  that  in  the  Bay  of  Baize  in  1538,  in  Cutch  in  1819, 
and  on  several  occasions  in  Peru  and  Chili,  since  the  commencement 
of  the  present  century,  the  permanent  upheaval  or  subsidence  of  land 
lias  been  accompanied  by  the  simultaneous  emission  of  lava  at  one  or 
more  points  in  the  same  volcanic  region.  From  these  and  other 
examples  it  may  be  inferred  that  the  rising  or  sinking  of  the  earth's 
crust,  operations  by  which  sea  is  converted  into  land,  and  land  into 
sea,  are  a  part  only  of  the  consequences  of  subterranean  igneous 
action.  It  can  scarcely  be  doubted  that  this  action  consists,  in  a  great 
degree,  of  the  baking,  and  occasionally  the  liquefaction,  of  rocks, 
causing  them  to  assume,  in  some  cases  a  larger,  in  others  a  smaller 
volume  than  before  the  application  of  heat.  It  consists  also  in  the 
generation  of  gases,  and  their  expansion  by  heat,  and  the  injection 
of  liquid  matter  into  rents  formed  in  superincumbent  rocks.  The 
prodigious  scale  on  which  these  subterranean  causes  have  operated 
in  Sicily  since  the  deposition  of  the  Newer  Pliocene  strata  will  be 
appreciated,  when  we  remember  that  throughout  half  the  surface  of 
that  island  such  strata  are  met  with,  raised  to  the  height  of  from  50 
to  that  of  2000  and  even  3000  feet  above  the  level  of  the  sea.  In 
the  same  island  also  the  older  rocks  which  are  contiguous  to  these 
marine  tertiary  strata  must  have  undergone,  within  the  same  period, 
a  similar  amount  of  upheaval. 

The  like  observations  may  be  extended  to  nearly  the  whole  of 
Europe,  for,  since  the  commencement  of  the  Eocene  period,  the 
entire  European  area,  including  some  of  the  central  and  very  lofty 
portions  of  the  Alps  themselves,  as  I  have  elsewhere  shown  f,  has, 
with  the  exception  of  a  few  districts,  emerged  from  the  deep  to  its 
present  altitude ;  and  even  those  tracts  which  were  already  dry  land 
before  the  Eocene  era  have  almost  everywhere  acquired  additional 
height.  A  large  amount  of  subsidence  has  also  occurred  during  the 
same  period,  so  that  the  extent  of  the  subterranean  spaces  which  have 

*  Darwin,  pp.  390.  406. ;  second  edi-  f  See  map  of  Europe  and  explana- 
tion, p.  319.  tion,  in  Principles,  book  i. 


CH.  XXXIV.]    PLUTONIC    ROCKS   OF   OOLITE   AND   LIAS.          585 

either  become  the  receptacles  of  sunken  fragments  of  the  earth's 
crust,  or  have  been  rendered  capable  of  supporting  other  fragments 
at  a  much  greater  height  than  before,  must  be  so  great  that  they 
probably  equal,  if  not  exceed  in  volume,  the  entire  continent  of 
Europe.  We  are  entitled,  therefore,  to  ask  what  amount  of  change 
of  equivalent  importance  can  be  proved  to  have  occurred  in  the 
earth's  crust  within  an  equal  quantity  of  time  anterior  to  the  Eocene 
epoch.  They  who  contend  for  the  more  intense  energy  of  subter- 
ranean causes  in  the  remoter  eras  of  the  earth's  history  may  find 
it  more  difficult  to  give  an  answer  to  this  question  than  they  anti- 
cipated. 

The  principal  effect  of  volcanic  action  in  the  nether  regions  during 
the  tertiary  period  seems  to  have  consisted  in  the  upheaval  to  the 
surface  of  hypogene  formations  of  an  age  anterior  to  the  carboni- 
ferous. The  repetition  of  another  series  of  movements,  of  equal  vio- 
lence, might  upraise  the  plutonic  and  metamorphic  rocks  of  many 
secondary  periods ;  and,  if  the  same  force  should  still  continue  to  act, 
the  next  convulsions  might  bring  up  to  the  day  the  tertiary  and 
recent  hypogene  rocks.  In  the  course  of  such  changes  many  of  the 
existing  sedimentary  strata  would  suffer  greatly  by  denudation, 
others  might  assume  a  metamorphic  structure,  or  become  melted 
down  into  plutonic  and  volcanic  rocks.  Meanwhile  the  deposition 
of  a  vast  thickness  of  new  strata  would  not  fail  to  take  place  during 
the  upheaval  and  partial  destruction  of  the  older  rocks.  But  I  must 
refer  the  reader  to  the  last  chapter  but  one  of  this  volume  for  a 
fuller  explanation  of  these  views. 

Cretaceous  period. — It  will  be  shown  in  the  next  chapter  that 
chalk,  as  well  as  lias,  has  been  altered  by  granite  in  the  eastern 
Pyrenees.  Whether  such  granite  be  cretaceous  or  tertiary  cannot 

easily  be  decided.  Suppose  b,  c,  d,  fig. 
Fi&  698-  698.,  to  be  three  members  of  the  Cre- 


taceous series,  the  lowest  of  which,  b, 
has  been  altered  by  the  granite  A,  the 
modifying   influence   not    having   ex- 
tended  so   far    as   c,   or  having   but 
slightly  affected  its  lowest  beds.     Now 
it  can  rarely  be  possible  for  the  geolo- 
gist to  decide  whether  the  beds  d  existed  at  the  time  of  the  intrusion 
of  A,  and  alteration  of  b  and  c,  or  whether  they  were  subsequently 
thrown  down  upon  c. 

But  as  some  Cretaceous  and  even  tertiary  rocks  have  been  raised 
to  the  height  of  more  than  9000  feet  in  the  Pyrenees,  we  must  not 
assume  that  plutonic  formations  of  the  same  periods  may  not  have 
been  brought  up  and  exposed  by  denudation,  at  the  height  of  2000 
or  3000  feet  on  the  flanks  of  that  chain. 

Period  of  Oolite  and  Lias.  —  In  the  department  of  the  Hautes 
Alpes,  in  France,  near  Vizille,  M.  Elie  de  Beaumont  traced  a  black 
argillaceous  limestone,  charged  with  belemnites,  to  within  a  few  yards 
of  a  mass  of  granite.  Here  the  limestone  begins  to  put  on  a  granular 


586 


PLUTONIC   KOCKS   OF   THE 


[Cn.  XXXIV. 


Fig.  699. 


texture,  but  is  extremely  fine-grained.  When  nearer  the  junction  it 
becomes  grey,  and  has  a  saccharoid  structure.  In  another  locality, 
near  Champoleon,  a  granite  composed  of  quartz,  black  mica,  and 
rose-coloured  felspar  is  observed  partly  to  overlie  the  secondary 
rocks,  producing  an  alteration  which  extends  for  about  30  feet 
downwards,  diminishing  in  the  beds  which  lie  farthest  from  the 

granite.  (See  fig.  699.)  In 
the  altered  mass  the  argil- 
laceous beds  are  hardened, 
the  limestone  is  saccharoid, 
the  grits  quartzose,  and  in 
the  midst  of  them  is  a 
thin  layer  of  an  imperfect 
granite.  It  is  also  an  im- 
portant circumstance  that 
near  the  point  of  contact, 
both  the  granite  and  the 
secondary  rocks  become 
metalliferous,  and  contain 
nests  and  small  veins  of 
blende,  galena,  iron,  and 
copper  pyrites.  The  stra- 
tified rocks  become  harder 


and  more  crystalline,  but 


Junction  of  granite  with  Jurassic  or  Oolite  strata  in  the 
Alps,  uear  Champoleon. 

the  granite,  on  the  contrary,  softer  and  less  perfectly  crystallized 
near  the  junction.* 

Although  the  granite  is  incumbent  in  the  above  section  (fig.  699.), 
we  cannot  assume  that  it  overflowed  the  strata,  for  the  disturbances 
of  the  rocks  are  so  great  in  this  part  of  the  Alps  that  they  seldom 
retain  the  position  which  they  must  originally  have  occupied. 

A  considerable  mass  of  syenite,  in  the  Isle  of  Skye,  is  described  by 
Dr.  MacCulloch  as  intersecting  limestone  and  shale,  which  are  of  the 
age  of  the  lias.f  The  limestone,  which  at  a  greater  distance  from 
the  granite  contains  shells,  exhibits  no  traces  of  them  near  its 
junction,  where  it  has  been  converted  into  a  pure  crystalline  marble.  J 

At  Predazzo,  in  the  Tyrol,  secondary  strata,  some  of  which  are 
limestones  of  the  Oolitic  period,  have  been  traversed  and  altered  by 
plutonic  rocks,  one  portion  of  which  is  an  augitic  porphyry,  which 
passes  insensibly  into  granite.  The  limestone  is  changed  into  gra- 
nular marble,  with  a  band  of  serpentine  at  the  j  unction.  § 

Carboniferous  period.  —  The  granite  of  Dartmoor,  in  Devonshire, 
was  formerly  supposed  to  be  one  of  the  most  ancient  of  the  plutonic 
rocks,  but  is  now  ascertained  to  be  posterior  in  date  to  the  culm- 
measures  of  that  county,  which  from  their  position,  and,  as  containing 


*  Elie  de  Beaumont,  sur  les  Mon- 
tagnes  de  1'Oisans,  &c.  Mem.  de  la 
Soc.  d'Hist.  Nat.  de  Paris,  torn.  v. 

f  Murchison,  Geol.  Trans.  2d  series, 
vol.  ii.  part  ii.  pp.  311 — 321. 


J  Western  Islands,    vol.    i.  p.  330. 
plate  18.,  figs.  3,  4. 

§  Von  Buch,  Annales  de  Chimie,  &c. 


~CH.  XXXIV.]    CARBONIFEROUS   AND   SILURIAN   PERIODS.       587 

true  coal-plants,  are  regarded  by  Professor  Sedgwick  and  Sir  R. 
Murchison  as  members  of  the  true  carboniferous  series.  This  granite, 
like  the  syenitic  granite  of  Christiania,  has  broken  through  the  stra- 
tified formations  without  much  changing  their  strike.  Hence,  on  the 
north-west  side  of  Dartmoor,  the  successive  members  of  the  culm- 
measures  abut  against  the  granite,  and  become  metamorphic  as  they 
approach.  These  strata  are  also  penetrated  by  granite  veins,  and 
plutonic  dikes,  called  "  elvans."  *  The  granite  of  Cornwall  is  pro- 
bably of  the  same  date,  and,  therefore,  as  modern  as  the  Carboniferous 
strata,  if  not  much  newer. 

Silurian  period. — It  has  long  been  known  that  the  granite  near 
Christiania,  in  Norway,  is  of  newer  origin  than  the  Silurian  strata  of 
that  region.  Von  Buch  first  announced,  in  1813,  the  discovery  of  its 
posteriority  in  date  to  limestones  containing  orthocerata  and  trilobites. 
The  proofs  consist  in  the  penetration  of  granite  veins  into  the  shale 
and  limestone,  and  the  alteration  of  the  strata,  for  a  considerable  dis- 
tance from  the  point  of  contact  both  of  these  veins  and  the  central 
mass  from  which  they  emanate.  (See  p.  577.)  Von  Buch  supposed 
that  the  plutonic  rock  alternated  with  the  fossiliferous  strata,  and 
that  large  masses  of  granite  were  sometimes  incumbent  upon  the 
strata ;  but  this  idea  was  erroneous,  and  arose  from  the  fact  that  the 
beds  of  shale  and  limestone  often  dip  towards  the  granite  up  to  the 
point  of  contact,  appearing  as  if  they  would  pass  under  it  in  mass,  as 
at  0,  fig.  700.,  and  then  again  on  the  opposite  side  of  the  same 
mountain,  as  at  b,  dip  away  from  the  same  granite.  When  the 
junctions,  however,  are  carefully  examined,  it  is  found  that  the  plu- 
tonic rock  intrudes  itself  in  veins,  and  nowhere  covers  the  fossiliferous 
strata  in  large  overlying  masses,  as  is  so  commonly  the  case  with 
trappean  formations,  f 

Fig.  700. 


Silurian.  Granite.  Silurian  strata. 

Now  this  granite,  which  is  more  modern  than  the  Silurian  strata  of 
Norway,  also  sends  veins  in  the  same  country  into  an  ancient  forma 
tion  of  gneiss ;  and  the  relations  of  the  plutonic  rock  and  the  gneiss, 
at  their  junction,  are  full  of  interest  when  we  duly  consider  the  wide 
difference  of  epoch  which  must  have  separated  their  origin. 

The  length  of  this  interval  of  time  is  attested  by  the  following 
facts: — The  fossiliferous,  or  Silurian,  beds  rest  unconformably 
upon  the  truncated  edges  of  the  gneiss,  the  inclined  strata  of  which 
had  been  denuded  before  the  sedimentary  beds  were  superimposed 

*  Proceed.  Geol.  Soc.,  vol.  ii.  p.  562.;  works  of  Keilhau,  with  whom  I  ex- 
and  Trans.  2d  ser.  vol.  v.  p.  686.  amined  this  country, 

f  See  the  Gaea  Norvegica  and  other 


588  OLDEST    GRANITE   ROCKS.  [Cn.  XXXIV. 

Fig.  701. 

Silurian  strata. 


Gneiss.  Granite.  Gneiss, 

Granite  sending  veins  into  Silurian  strata  and  Gneiss, —  Christiania,  Norway. 

(see  fig.  701.).  The  signs  of  denudation  are  twofold;  first,  the 
surface  of  the  gneiss  is  seen  occasionally,  on  the  removal  of  the 
newer  beds,  containing  organic  remains,  to  be  worn  and  smoothed ; 
secondly,  pebbles  of  gneiss  have  been  found  in  some  of  these  Silurian 
strata.  Between  the  origin,  therefore,  of  the  gneiss  and  the  granite 
there  intervened,  first,  the  period  when  the  strata  of  gneiss  were 
denuded ;  secondly,  the  period  of  the  deposition  of  the  Silurian  de- 
posits. Yet  the  granite  produced  after  this  long  interval  is  often  so 
intimately  blended  with  the  ancient  gneiss,  at  the  point  of  junction, 
that  it  is  impossible  to  draw  any  other  than  an  arbitrary  line  of 
separation  between  them ;  and  where  this  is  not  the  case,  tortuous 
veins  of  granite  pass  freely  through  gneiss,  ending  sometimes  in 
threads,  as  if  the  older  rock  had  offered  no  resistance  to  their  passage. 
It  seems  necessary,  therefore,  to  conceive  that  the  gneiss  was  softened 
and  more  or  less  melted  when  penetrated  by  the  granite.  But  had 
such  junctions  alone  been  visible,  and  had  we  not  learnt,  from  other 
sections,  how  long  a  period  elapsed  between  the  consolidation  of  the 
gneiss  and  the  injection  of  this  granite,  we  might  have  suspected 
that  the  gneiss  was  scarcely  solidified,  or  had  not  yet  assumed  its 
complete  metamorphic  character  when  invaded  by  the  plutonic  rock. 
From  this  example  we  may  learn  how  impossible  it  is  to  conjecture 
whether  certain  granites  in  Scotland,  and  other  countries,  which 
send  veins  into  gneiss  and  other  metamorphic  rocks,  are  primary,  or 
whether  they  may  not  belong  to  some  secondary  or  tertiary  period. 

Oldest  granites.  —  It  is  not  half  a  century  since  the  doctrine  was 
very  general  that  all  granitic  rocks  were  primitive,  that  is  to  say,  that 
they  originated  before  the  deposition  of  the  first  sedimentary  strata, 
and  before  the  creation  of  organic  beings  (see  above,  p.  9.).  But  so 
greatly  are  our  views  now  changed,  that  we  find  it  no  easy  task  to 
point  out  a  single  mass  of  granite  demonstrably  more  ancient  than  all 
the  known  fossiliferous  deposits.  Could  we  discover  some  Lower 
Cambrian  strata  resting  immediately  on  granite,  there  being  no  alter- 
ations at  the  point  of  contact,  nor  any  intersecting  granitic  veins,  we 
might  then  affirm  the  plutonic  rock  to  have  originated  before  the 
oldest  known  fossiliferous  strata.  Still  it  would  be  presumptuous, 
as  we  have  already  pointed  out  (p.  456.),  to  suppose  that  when  a 
small  part  only  of  the  globe  has  been  investigated,  we  are  acquainted 
with  the  oldest  fossiliferous  strata  in  the  crust  of  our  planet.  Even 
when  these  are  found,  we  cannot  assume  that  there  never  were  any 
antecedent  strata  containing  organic  remains,  which  may  have 


'Cn.  XXXIV.]    AGE  OF  GRANITES  OP  ARRAN.  589 

become  metamorphic.  If  we  find  pebbles  of  granite  in  a  conglo- 
merate of  the  Lower  Cajnbrian  system,  we  may  then  feel  assured  that 
the  parent  granite  was  formed  before  the  Lower  Cambrian  formation. 
But  if  the  incumbent  strata  be  merely  Silurian  or  Upper  Cambrian, 
the  fundamental  granite,  although  of  high  antiquity,  may  be  posterior 
in  date  to  known  fossiliferous  formations. 

Protrusion  of  solid  granite. — In  part  of  Sutherlandshire,  near 
Brora,  common  granite,  composed  of  felspar,  quartz,  and  mica,  is  in 
immediate  contact  with  Oolitic  strata,  and  has  clearly  been  elevated 
to  the  surface  at  a  period  subsequent  to  the  deposition  of  those  strata.* 
Professor  Sedgwick  and  Sir  R.  Murchison  conceive  that  this  granite 
has  been  upheaved  in  a  solid  form ;  and  that  in  breaking  through  the 
submarine  deposits,  with  which  it  was  not  perhaps  originally  in  con- 
tact, it  has  fractured  them  so  as  to  form  a  breccia  along  the  line  of 
junction.  This  breccia  consists  of  fragments  of  shale,  sandstone,  and 
limestone,  with  fossils  of  the  oolite,  all  united  together  by  a  calcareous 
cement.  The  secondary  strata,  at  some  distance  from  the  granite, 
are  but  slightly  disturbed,  but  in  proportion  to  their  proximity  the 
amount  of  dislocation  becomes  greater. 

If  we  admit  that  solid  hypogene  rocks,  whether  stratified  or  un- 
stratified,  have  in  such  cases  been  driven  upwards  so  as  to  pierce 
through  yielding  sedimentary  deposits,  we  shall  be  enabled  to  account 
for  many  geological  appearances  otherwise  inexplicable.  Thus,  for 
example,  at  Weinbohla  and  Hohnstein,  near  Meissen,  in  Saxony,  a 
mass  of  granite  has  been  observed  covering  strata  of  the  Cretaceous 
and  Oolitic  periods  for  the  space  of  between  300  and  400  yards 
square.  It  appears  clearly  from  a  memoir  of  Dr.  B.  Cotta  on  this 
subject  f,  that  the  granite  was  thrust  into  its  actual  position  when 
solid.  There  are  no  intersecting  veins  at  the  junction, — no  alteration 
as  if  by  heat,  but  evident  signs  of  rubbing,  and  a  breccia  in  some 
places,  in  which  pieces  of  granite  are  mingled  with  broken  fragments 
of  the  secondary  rocks.  As  the  granite  overhangs  both  the  lias  and 
chalk,  so  the  lias  is  in  some  places  bent  over  strata  of  the  cretaceous  era. 

Relative  age  of  the  granites  of  Arran.  —  In  this  island,  the  largest 
in  the  Firth  of  Clyde,  being  twenty  miles  in  length  from  north  to 
south,  the  four  great  classes  of  rocks,  the  fossiliferous,  volcanic,  plu- 
tonic,  and  metamorphic,  are  all  conspicuously  displayed  within  a 
very  small  area,  and  with  their  peculiar  characters  strongly  con- 
tr^isted.  In  the  north  of  the  island  the  granite  rises  to  the  height 
of  nearly  3000  feet  above  the  sea,  terminating  in  mountainous  peaks. 
(See  section,  fig.  702.).  On  the  flanks  of  the  same  mountains  are 
chloritic-schists,  blue  roofing-slate,  and  other  rocks  of  the  metamor- 
phic order  (No.  1.),  into  which  the  granite  (No.  2.)  sends  veins. 
This  granite,  therefore,  is  newer  than  the  hypogene  schists  (No.  1.), 
which  it  penetrates. 

These  schists  are  highly  inclined.     Upon  them  rest  beds  of  con- 

*  Murchison,  Geol.  Trans.,  2d  series,  f  Geognostische  Wanderungen,  Leip- 
vol.  ii.  p.  307.  zig,  1838. 


590  AGE   OF   THE   GRANITES  [Cn.  XXXIV. 

glomerate  and  sandstone  (No.  3.),  which  are  referable  to  the  Old 
Red  formation,  to  which  succeed  various  shales  and  limestones 
(No.  4.)  containing  the  fossils  of  the  Carboniferous  period,  upon 
which  are  other  strata  of  sandstone  and  conglomerate  (upper  part  of 
No.  4.),  in  which  no  fossils  have  been  met  with,  which  it  is  con- 
jectured may  belong  to  the  New  Red  sandstone  period.  All  the 
preceding  formations  are  cut  through  by  the  volcanic  rocks  (No.  5.), 
which  consist  of  greenstone,  basalt,  pitchstone,  claystone-porphyry, 
and  other  varieties.  These  appear  either  in  the  form  of  dikes,  or  in 
dense  masses  from  50  to  700  feet  in  thickness,  overlying  the  strata 
(No.  4.).  They  sometimes  pass  into  syenite  of  so  crystalline  a  form, 
that  it  may  rank  as  a  plutonic  formation ;  and  in  one  region,  at 
Ploverfield,  in  Glen  Cloy,  a  fine-grained  granite  (6.  a)  is  seen  asso- 
ciated with  the  trap  formation,  and  sending  veins  into  the  sandstone 
or  into  the  upper  strata  of  No.  4.  This  interesting  discovery  ot 
granite  in  the  southern  region  of  Arran,  at  a  point  where  it  is  sepa- 
rated from  the  northern  mass  of  granite  by  a  great  thickness  of 
secondary  strata  and  overlying  trap,  was  made  by  Mr.  L.  A.  Necker 
of  Geneva,  during  his  survey  of  Arran  in  1839.  We  also  learn  from 
later  investigations  by  Prof.  A.  C.  Ramsay,  that  a  similar  fine- 
grained granite  (No.  6.  b)  appears  in  the  interior  of  the  northern 
granitic  district,  forming  the  nucleus  of  it,  and  sending  veins  into 
the  older  coarse-grained  granite  (No.  2.).  The  trap  dikes  which 
penetrate  the  older  granite  are  cut  off,  according  to  Mr.  Ramsay,  at 
the  junction  of  the  fine  grained. 

It  is  not  improbable  that  the  granite  (No.  6.  £),  may  be  of  the 
same  age  as  that  of  Ploverfield  (No.  6.  «.),  and  this  again  may  belong 
to  the  same  geological  epoch  as  the  trap  formations  (No.  5.).  If 
there  be  any  difference  of  date,  it  would  seem  that  the  fine-grained 
granite  must  be  newer  than  the  trappean  rocks.  But,  on  the  other 
hand,  the  coarser  granite  (No.  2.)  may  be  the  oldest  rock  in  Arran, 
with  the  exception  of  the  hypogene  slates  (No.  1.),  into  which  it 
sends  veins. 

An  objection  may  perhaps  at  first  be  started  to  this  conclusion, 
derived  from  the  curious  and  striking  fact,  the  importance  of  which 
was  first  emphatically  pointed  out  by  Dr.  MacCulloch,  that  no 
pebbles  of  granite  occur  in  the  conglomerates  of  the  red  sandstone 
in  Arran,  although  these  conglomerates  are  several  hundred  feet  in 
thickness,  and  lie  at  the  foot  of  lofty  granite  mountains,  which  tower 
above  them.  As  a  general  rule,  all  such  aggregates  of  pebbles  and 
sand  are  mainly  composed  of  the  wreck  of  pre-existing  rocks  occur- 
ring in  the  immediate  vicinity.  The  total  absence  therefore  of  gra- 
nitic pebbles  has  justly  been  a  theme  of  wonder  to  those  geologists 
who  have  successively  visited  Arran,  and  they  have  carefully  searched 
there,  as  I  have  done  myself,  to  find  an  exception,  but  in  vain.  The 
rounded  masses  consist  exclusively  of  quartz,  chlorite -schist,  and 
other  members  of  the  metamorphic  series  ;  nor  in  the  newer  conglo- 
merates of  No.  4.  have  any  granitic  fragments  been  discovered.  Are 
we  then  entitled  to  affirm  that  the  coarse-grained  granite  (No.  2.),  like 


CH.  XXXIV.] 


OF   THE  ISLE   OP  ARKAN. 


591 


c  —i  « 

ll 


1! 

11! 

HI 
HI 


jl 


pP8i3 


«Neo      •*«•,=  < 


592  GRANITES   OF   ARRAN.  [Cn.  XXXIV. 

the  fine-grained  variety  (No.  6.  «),  is  more  modern  than  all  the  other 
rocks  of  the  island  ?  This  we  cannot  assume  at  present,  but  we  may 
confidently  infer  that  when  the  various  beds  of  sandstone  and  con- 
glomerate were  formed,  no  granite  had  reached  the  surface,  or  had 
been  exposed  to  denudation  in  Arran.  It  is  clear  that  the  crystalline 
schists  were  ground  into  sand  and  shingle  when  the  strata  No.  3. 
were  deposited,  and  at  that  time  the  waves  had  never  acted  upon  the 
granite,  which  now  sends  its  veins  into  the  schist.  May  we  then 
conclude,  that  the  schists  suffered  denudation  before  they  were  in- 
vaded by  granite  ?  This  opinion,  although  not  inadmissible,  is  by 
no  means  fully  borne  out  by  the  evidence.  For  at  the  time  when 
the  Old  Red  Sandstone  originated,  the  metamorphic  strata  may  have 
formed  islands  in  the  sea,  as  in  fig.  703.,  over  which  the  breakers 

Fig.  703. 
Sea, 


rolled,  or  from  which  torrents  and  rivers  descended,  carrying  down 
gravel  and  sand.  The  plutonic  rock  or  granite  (B)  may  even  then 
have  been  previously  injected  at  a  certain  depth  below,  and  yet  may 
never  have  been  exposed  to  denudation. 

As  to  the  time  and  manner  of  the  subsequent  protrusion  of  the 
coarse-grained  granite  (No.  2.),  this  rock  may  have  been  thrust  up 
bodily,  in  a  solid  form,  during  that  long  series  of  igneous  operations 
which  produced  the  trappean  and  plutonic  formations  (Nos.  5.,  6.  «, 
and  6.  b). 

We  have  shown  that  these  eruptions,  whatever  their  date,  were 
posterior  to  the  deposition  of  all  the  fossiliferous  strata  of  Arrau. 
We  can  also  prove  that  subsequently  both  the  granitic  and  trappean 
rocks  underwent  great  aqueous  denudation,  which  they  probably 
suffered  during  their  emergence  from  the  sea.  The  fact  is  demon- 
strated by  the  abrupt  truncation  of  numerous  dikes,  such  as  those  at 
c,  d,  e,  which  are  cut  off  on  the  surface  of  the  granite  and  trap.  The 
overlying  trap  also  ceases  very  abruptly  on  approaching  the  boundary 
of  the  great  hypogene  region,  and  termina'tes  in  a  steep  escarpment 
facing  towards  it  as  at  /,  fig.  702.  When  in  its  original  fluid  state 
it  could  not  have  come  thus  suddenly  to  an  end,  but  must  have  filled 
up  the  hollow  now  separating  it  from  the  hypogene  rocks,  had  such 
a  hollow  then  existed.  This  necessity  of  supposing  that  both  the 
trap  and  the  conglomerate  once  extended  farther,  and  that  veins  such 
as  c,  d,  fig.  702.,  were  once  prolonged  farther  upwards,  prepares  us 
to  believe  that  the  whole  of  the  northern  granite  may  at  one  time 
have  been  covered  by  newer  formations,  under  the  pressure  of  which, 
before  its  protrusion,  it  assumed  its  highly  crystalline  texture. 

The  theory  of  the  protrusion  in  a  solid  form  of  the  northern 
nucleus  of  granite  is  confirmed  by  the  manner  in  which  the  hypogene 
slates  (No.  1.)  and  the  beds  of  conglomerate  (No.  3.)  dip  away  from 


Og.  XXXIV.]  THE   ISLE   OP   ARRAN.  593 

it  on  all  sides.  In  some  places  indeed  the  slates  are  inclined  towards 
the  granite,  but  this  exception  might  have  been  looked  for,  because 
these  hypogene  strata  have  undergone  disturbances  at  more  than  one 
geological  epoch,  and  may  at  some  points,  perhaps,  have  their  original 
order  of  position  inverted.  The  high  inclination,  therefore,  and  the 
quaquaversal  dip  of  the  beds  around  the  borders  of  the  granitic  boss, 
and  the  comparative  horizontality  of  the  fossiliferous  strata  in  the 
southern  part  of  the  island,  are  facts  which  all  accord  with  the  hypo- 
thesis of  a  great  amount  of  movement  at  that  point  where  the  granite 
is  supposed  to  have  been  thrust  up  bodily,  and  where  we  may  con- 
ceive it  to  have  been  distended  laterally  by  the  repeated  injection  of 
fresh  supplies  of  melted  materials.* 

*  For  the  geology  of  Arran  consult  Keeker's  Memoir,   read  to  the  Royal 

the  works  of  Drs.  Hutton  and  MacCul-  Soc.  of  Edin.  20th  April,  1840,  and  Mr. 

loch,    the    Memoirs    of   Messrs.    Vou  Ramsay's  Geol.  of  Arran,  1841.     I  ex- 

Dechen  and  Oeynhausen,  that  of  Pro-  amined  myself  a  large  part  of  Arran 

fessor  Sedgwick  and  SirR.  Murchison  in  1836. 
(Geol.  Trans.  2d  series)    Mr.  L.  A. 


Q    Q 


594  METAMORPHIC   ROCKS.  [Cn.  XXXV. 


CHAPTER  XXXV. 

METAMORPHIC   ROCKS. 

General  character  of  metamorphic  rocks  —  Gneiss  —  Hornblende-schist  —  Mica- 
schist  —  Clay-slate  —  Quartzite  —  Chlorite-schist  —  Metamorphic  limestone  — 
Alphabetical  list  and  explanation  of  the  more  abundant  rocks  of  this  family 
— Origin  of  the  metamorphic  strata  —  Their  stratification  —  Fossiliferous  strata 
near  intrusive  masses  of  granite  converted  into  rocks  identical  with  different 
members  of  the  metamorphic  series  —  Arguments  hence  derived  as  to  the 
nature  of  plutonic  action  —  Time  may  enable  this  action  to  pervade  denser 
masses  — From  what  kinds  of  sedimentary  rock  each  variety  of  the  metamorphic 
class  may  be  derived  —  Certain  objections  to  the  metamorphic  theory  considered 
—  Partial  conversion  of  Eocene  slate  into  gneiss. 

WE  have  now  considered  three  distinct  classes  of  rocks :  first,  the 
aqueous,  or  fossiliferous  ;  secondly,  the  volcanic ;  and,  thirdly,  the 
plutonic,  or  granitic ;  and  we  have  now,  lastly,  to  examine  those 
crystalline  (or  hypogene)  strata  to  which  the  name  of  metamorphic 
has  been  assigned.  The  last-mentioned  term  expresses,  as  before 
explained,  a  theoretical  opinion  that  such  strata,  after  having  been 
deposited  from  water,  acquired,  by  the  influence  of  heat  and  other 
causes,  a  highly  crystalline  texture.  They  who  still  question  this 
opinion  may  call  the  rocks  under  consideration  the  stratified  hypo- 
gene,  or  schistose  hypogene  formations. 

These  rocks,  when  in  their  most  characteristic  or  normal  state,  are 
wholly  devoid  of  organic  remains,  and  contain  no  distinct  fragments 
of  other  rocks,  whether  rounded  or  angular.  They  sometimes  break 
out  in  the  central  parts  of  narrow  mountain  chains,  but  in  other 
cases  extend  over  areas  of  vast  dimensions,  occupying,  for  example, 
nearly  the  whole  of  Norway  and  Sweden,  where,  as  in  Brazil,  they 
appear  alike  in  the  lower  and  higher  grounds.  In  Great  Britain, 
those  members  of  the  series  which  approach  most  nearly  to  granite 
in  their  composition,  as  gneiss,  mica-schist,  and  hornblende -schist, 
are  confined  to  the  country  north  of  the  rivers  Forth  and  Clyde. 

However  crystalline  these  rocks  may  become  in  certain  regions, 
they  never,  like  granite  or  trap,  send  veins  into  contiguous  forma- 
tions, whether  into  an  older  schist  or  granite  or  into  a  set  of  newer 
fossiliferous  strata. 

Many  attempts  have  been  made  to  trace  a  general  order  of  suc- 
cession or  superposition  in  the  members  of  this  family  ;  clay-slate, 
for  example,  having  been  often  supposed  to  hold  invariably  a  higher 
geological  position  than  mica-schist,  and  mica-schist  always  to 
overlie  gneiss.  But  although  such  an  order  may  prevail  through- 


Cfi.  XXXV.]  GNEISS  —  HORNBLENDE-SCHIST.  595 

out  limited  districts,  it  is  by  no  means  universal.  To  this  subject, 
however,  I  shall  again  revert,  in  the  37th  chapter,  when  the  chro- 
nological relations  of  the  metamorphic  rocks  are  pointed  out. 

The  following  may  be  enumerated  as  the  principal  members  of  the 
metamorphic  class  :  — gneiss,  mica-schist,  hornblende-schist,  clay- 
slate,  chlorite-schist,  hypogene  or  metamorphic  limestone,  and  certain 
kinds  of  quartz-rock  or  quartzite. 

Gneiss.  —  The  first  of  these,  gneiss,  may  be  called  stratified,  or,  by 
those  who  object  to  that  term,  foliated,  granite,  being  formed  of  the 
same  materials  as  granite,  namely,  felspar,  quartz,  and  mica.  In  the 
specimen  here  figured,  the  white  layers  consist  almost  exclusively  of 
granular  felspar,  with  here  and  there  a  speck  of  mica  and  grain  of 
quartz.  The  dark  layers  are  composed  of  grey  quartz  and  black 

Fig.  704. 


Fragment  of  gneiss,  natural  size  :  section  made  at  right  angles  to 
the  planes  of  foliation. 

mica,  with  occasionally  a  grain  of  felspar  intermixed.  The  rock 
splits  most  easily  in  the  plane  of  these  darker  layers,  and  the  surface 
thus  exposed  is  almost  entirely  covered  with  shining  spangles  of 
mica.  The  accompanying  quartz,  however,  greatly  predominates  in 
quantity,  but  the  most  ready  cleavage  is  determined  by  the  abun- 
dance of  mica  in  certain  parts  of  the  dark  layer. 

Instead  of  consisting  of  these  thin  laminae,  gneiss  is  sometimes 
simply  divided  into  thick  beds,  in  which  the  mica  has  only  a  slight 
degree  of  parallelism  to  the  planes  of  stratification. 

The  term  "gneiss,"  however,  in  geology  is  commonly  used  in  a 
wider  sense,  to  designate  a  formation  in  which  the  above-mentioned 
rock  prevails,  but  with  which  any  one  of  the  other  metamorphic 
rocks,  and  more  especially  hornblende-schist,  may  alternate.  These 
other  members  of  the  metamorphic  series  are,  in  this  case,  considered 
as  subordinate  to  the  true  gneiss. 

The  different  varieties  of  rock  allied  to  gneiss,  into  which  felspar 
enters  as  an  essential  ingredient,  will  be  understood  by  referring  to 
what  was  said  of  granite.  Thus,  for  example,  hornblende  may  be 
superadded  to  mica,  quartz,  and  felspar,  forming  a  syenitic  gneiss  ; 
or  talc  may  be  substituted  for  mica,  constituting  talcose  gneiss,  a 
rock  composed  of  felspar,  quartz,  and  talc,  in  distinct  crystals  or 
grains  (stratified  protogine  of  the  French). 

Hornblende-schist  is  usually  black,  and  composed  principally  of 
hornblende,  with  a  variable  quantity  of  felspar,  and  sometimes  grains 

QQ  2 


596  MICA-SCHIST,    CLAY-SLATE,    ETC.          [Ca.  XXXV. 

of  quartz.  When  the  hornblende  and  felspar  are  nearly  in  equal 
quantities,  and  the  rock  is  not  slaty,  it  corresponds  in  character  with 
the  greenstones  of  the  trap  family,  and  has  been  called  "  primitive 
greenstone."  It  may  be  termed  hornblende  rock.  Some  of  these 
hornblendic  masses  may  really  have  been  volcanic  rocks,  which  have 
since  assumed  a  more  crystalline  or  metamorphic  texture. 

Mica-schist,  or  Micaceous  schist,  is,  next  to  gneiss,  one  of  the  most 
abundant  rocks  of  the  metamorphic  series.  It  is  slaty,  essentially 
composed  of  mica  and  quartz,  the  mica  sometimes  appearing  to  con- 
stitute the  whole  mass.  Beds  of  pure  quartz  also  occur  in  this 
formation.  In  some  districts,  garnets  in  regular  twelve-sided  crystals 
form  an  integrant  part  of  mica-schist.  This  rock  passes  by  insensible 
gradations  into  clay-slate. 

Clay-slate,  or  Argillaceous  schist. — This  rock  sometimes  resembles 
an  indurated  clay  or  shale.  It  is  for  the  most  part  extremely  fissile, 
often  affording  good  roofing-slate.  Occasionally  it  derives  a  shining 
and  silky  lustre  from  the  minute  particles  of  mica  or  talc  which  it 
contains.  It  varies  from  greenish  or  bluish -grey  to  a  lead  colour ; 
and  it  may  be  said  of  this,  more  than  of  any  other  schist,  that  it  is 
common  to  the  metamorphic  and  fossiliferous  series,  for  some  clay- 
slates  taken  from  each  division  would  not  be  distinguishable  by 
mineral  characters  alone. 

Quartzite,  or  Quartz  rock,  is  an  aggregate  of  grains  of  quartz 
which  are  either  in  minute  crystals,  or  in  many  cases  slightly 
rounded,  occurring  in  regular  strata,  associated  with  gneiss  or  other 
metamorphic  rocks.  Compact  quartz,  like  that  so  frequently  found 
in  veins,  is  also  found  together  with  granular  quartzite.  Both  of 
these  alternate  with  gneiss  or  mica-schist,  or  pass  into  those  rocks 
by  the  addition  of  mica,  or  of  felspar  and  mica. 

Chlorite-schist  is  a  green  slaty  rock,  in  which  chlorite  is  abundant 
in  foliated  plates,  usually  blended  with  minute  grains  of  quartz,  or 
sometimes  with  felspar  or  mica ;  often  associated  with,  and  gra- 
duating into,  gneiss  and  clay-slate. 

Crystalline  or  Metamorphic  limestone.  —  This  hypogene  rock, 
called  by  the  earlier  geologists  primary  limestone,  is  sometimes  a 
white  crystalline  granular  marble,  which  when  in  thick  beds  can  be 
used  in  sculpture  ;  but  more  frequently  it  occurs  in  thin  beds,  form- 
ing a  foliated  schist  much  resembling  in  colour  and  appearance 
certain  varieties  of  gneiss  and  mica-schist. '  When  it  alternates  with 
these  rocks,  it  often  contains  some  crystals  of  mica,  and  occasionally 
quartz,  felspar,  hornblende,  talc,  chlorite,  garnet,  and  other  minerals. 
It  enters  sparingly  into  the  structure  of  the  hypogene  districts 
of  Norway,  Sweden,  and  Scotland,  but  is  largely  developed  in  the 
Alps. 

Before  offering  any  farther  observations  on  the  probable  origin  of 
the  metamorphic  rocks,  I  subjoin,  in  the  form  of  a  glossary,  a  brief 
explanation  of  some  of  the  principal  varieties  and  their  synonyms. 


Ci.  XXXV.]  METAMORPHIC   ROCKS.  597 

Explanation  of  the  Names,  Synonyms,  and  Mineral  Composition  of 
the  more  abundant  Metamorphic  Rocks. 

ACTINOLITE-SCHIST.  A  slaty  foliated  rock,  composed  chiefly  of  actinolite,  (an 
emerald-green  mineral,  allied  to  hornblende,)  with  some  admixture  of 
garnet,  mica,  and  quartz. 

AMPELITE.  Aluminous  slate  (Brongniart)  ;  occurs  both  in  the  metamorphic  and 
fossiliferous  series. 

AMPHIBOLITE,     Hornblende  rock,  which  see. 

ARGILLACEOUS-SCHIST,  or  CLAT-SLATE.     See  p.  596. 

ARKOSE.  Name  given  by  Brongniart  to  a  compound  of  the  same  materials  as 
granite,  which  it  often  resembles  closely.  It  is  found  at  the  junction  of 
granite  with  formations  of  different  ages,  and  consists  of  crystals  of  felspar, 
quartz,  and  sometimes  mica,  which,  after  separation  from  their  original 
matrix  by  disintegration,  have  been  reunited  by  a  siliceous  or  quartzose 
cement.  It  is  often  penetrated  by  quartz  veins. 

CHIASTOLITE-SLATE  scarcely  differs  from  clay-slate,  but  includes  numerous  crystals 
of  Chiastolite  :  in  considerable  thickness  in  Cumberland.  Chiastolite 
occurs  in  long  slender  rhomboidal  crystals.  For  composition,  •  see  Table, 
p.  479. 

CHLORITE-SCHIST.  A  green  slaty  rock,  in  which  chlorite,  a  green  scaly  mineral, 
is  abundant.  See  p.  596. 

CLAY-SLATE  or  ARGILLACEOUS-SCHIST.     See  p.  596. 

EURITE  has  been  already  mentioned  as  a  plutonic  rock  (p.  569.),  but  occurs  also 
with  precisely  the  same  composition  in  beds  subordinate  to  gneiss  or  mica- 
slate. 

GNEISS.  A  stratified  or  foliated  rock  ;  has  the  same  composition  as  granite.  See 
p.  595. 

HORNBLENDE  KOCK,  or  AMPHIBOLITE.  See  above,  p.  477.  A  member  both  of 
the  volcanic  and  metamorphic  series.  Agrees  in  composition  with  horn- 
blende-schist, but  is  not  fissile. 

HORNBLENDE-SCHIST,  or  SLATE.  Composed  of  hornblende  and  felspar.  Sec 
p.  595. 

HORNBLENDIC  or  STENiTic  GNEISS.  Composed  of  felspar,  quartz,  and  horn- 
blende. 

HYPOGENE  LIMESTONE.     See  p.  596. 

MARBLE.     See  pp.  12.  &  596. 

MICA-SCHIST,  or  MICACEOUS-SCHIST.      A   slaty  rock,    composed  of  mica  and 

quartz,  in  variable  proportions.     See  p.  596. 
MICA-SLATE.     See  MICA-SCHIST,  p.  596. 

PHYLLADE.    D'Aubuisson's  term  for  clay-slate,  from  <f>tAX«f,  a  heap  of  leaves. 
PRIMARY  LIMESTONE.     See  HYPOGENE  LIMESTONE,  p.  596. 
PROTOGINE.     See   TALCOSE-GNEISS,  p.   595. ;  when  unstratified   it   is    Talcose- 
granite. 

QUARTZ  KOCK,  or  QUARTZTTE.  A  stratified  rock  ;  an  aggregate  of  grains  of 
quartz.  See  p.  596. 

SERPENTINE  has  already  been  described  (p.  478.)  because  it  occurs  in  both  divi- 
sions of  the  hypogene  series,  as  a  stratified  or  unstratified  rock. 

TALCOSE-GNEISS.  Same  composition  as  talcose-granite  or  protogine,  but  stratified 
or  foliated.  See  p.  595. 

TALCOSE-SCHIST  consists  chiefly  of  talc,  or  of  talc  and  quartz,  or  of  talc  and  fel- 
spar, and  has  a  texture  something  like  that  of  clay-slate. 
QQ  3 


598  METAMOEPHIC   EOCKS.  [Cn.  XXXV. 

Origin  of  the  Metamorphic  Strata. 

Having  said  thus  much  of  the  mineral  composition  of  the  meta- 
morphic  rocks,  I  may  combine  what  remains  to  be  said  of  their 
structure  and  history  with  an  account  of  the  opinions  entertained  of 
their  probable  origin.  At  the  same  time,  it  may  be  well  to  forewarn 
the  reader  that  we  are  here  entering  upon  ground  of  controversy, 
and  soon  reach  the  limits  where  positive  induction  ends,  and  beyond 
which  we  can  only  indulge  in  speculations.  It  was  once  a  favourite 
doctrine,  and  is  still  maintained  by  many,  that  these  rocks  owe  their 
crystalline  texture,  their  want  of  all  signs  of  a  mechanical  origin,  or 
of  fossil  contents,  to  a  peculiar  and  nascent  condition  of  the  planet  at 
the  period  of  their  formation.  The  arguments  in  refutation  of  this 
hypothesis  will  be  more  fully  considered  when  I  show,  in  the  last 
chapter  of  this  volume,  to  how  many  different  ages  the  metamorphic 
formations  are  referable,  and  how  gneiss,  mica-schist,  clay -slate,  and 
hypogene  limestone  (that  of  Carrara  for  example)  have  been  formed, 
not  only  since  the  first  introduction  of  organic  beings  into  this  planet, 
but  even  long  after  many  distinct  races  of  plants  and  animals  had 
passed  away  in  succession. 

The  doctrine  respecting  the  crystalline  strata,  implied  in  the 
name  metamorphic,  may  properly  be  treated  of  in  this  place ;  and 
we  must  first  inquire  whether  these  rocks  are  really  entitled  to  be 
called  stratified  in  the  strict  sense  of  having  been  originally  de- 
posited as  sediment  from  water.  The  general  adoption  by  geologists 
of  the  term  stratified,  as  applied  to  these  rocks,  sufficiently  attests 
their  division  into  beds  very  analogous,  at  least  in  form,  to  ordinary 
fossiliferous  strata.  This  resemblance  is  by  no  means  confined  to 
the  existence  in  both  occasionally  of  a  laminated  structure,  but  ex- 
tends to  every  kind  of  arrangement  which  is  compatible  with  the 
absence  of  fossils,  and  of  sand,  pebbles,  ripple-mark,  and  other  cha- 
racters which  the  metamorphic  theory  supposes  to  have  been  ob- 
literated by  plutonic  action.  Thus,  for  example,  we  behold  alike  in 
the  crystalline  and  fossiliferous  formations  an  alternation  of  beds 
varying  greatly  in  composition,  colour,  and  thickness.  We  observe, 
for  instance,  gneiss  alternating  with  layers  of  black  hornblende- 
schist,  or  of  green  chlorite-schist,  or  with  granular  quartz,  or  lime- 
stone ;  and  the  interchange  of  these  different  strata  may  be  repeated 
for  an  indefinite  number  of  times.  In  the  like  manner,  mica-schist 
alternates  with  chlorite-schist,  and  with  beds  of  pure  quartz  or  of 
granular  limestone. 

We  have  already  seen  that,  near  the  immediate  contact  of  granitic 
veins  and  volcanic  dikes,  very  extraordinary  alterations  in  rocks 
have  taken  place,  more  especially  in  the  neighbourhood  of  granite. 
It  will  be  useful  here  to  add  other  illustrations,  showing  that  a  tex- 
ture undistinguishable  from  that  which  characterizes  the  more 
crystalline  metamorphic  formations  has  actually  been  superinduced 
in  strata  once  fossiliferous. 


CH.  XXXV.]       STRATA   IN    CONTACT   WITH   GEANITE. 


599 


In  the  southern  extremity  of  Norway  there  is  a  large  district,  on 
the  west  side  of  the  fiord  of  Christiania,  in  which  granite  or  syenite 
protrudes  in  mountain  masses  through  fossiliferous  strata,  and  usually 
sends  veins  into  them  at  the  point  of  contact.  The  stratified  rocks, 
replete  with  shells  and  zoophytes,  consist  chiefly  of  shale,  limestone, 
and  some  sandstone,  and  all  these  are  invariably  altered  near  the 
granite  for  a  distance  of  from  50  to  400  yards.  The  aluminous 
shales  are  hardened  and  have  become  flinty.  Sometimes  they  re- 
semble jasper.  Ribboned  jasper  is  produced  by  the  hardening  of 
alternate  layers  of  green  and  chocolate-coloured  schist,  each  stripe 
faithfully  representing  the  original  lines  of  stratification.  Nearer 
the  granite  the  schist  often  contains  crystals  of  hornblende,  which 
are  even  met  with  in  some  places  for  a  distance  of  several  hundred 
yards  from  the  junction ;  and  this  black  hornblende  is  so  abundant 
that  eminent  geologists,  when  passing  through  the  country,  have 
confounded  it  with  the  ancient  hornblende-schist,  subordinate  to  the 
great  gneiss  formation  of  Norway.  Frequently,  between  the  granite 
ind  the  hornblende  slate,  above-mentioned,  grains  of  mica  and  crys- 
talline felspar  appear  in  the  schist,  so  that  rocks  resembling  gneiss 
ind  mica-schist  are  produced.  Fossils  can  rarely  be  detected  in 
these  schists,  and  they  are  more  completely  effaced  in  proportion  to 
1he  more  crystalline  texture  of  the  beds,  and  their  vicinity  to  the 
granite.  In  some  places  the  siliceous  matter  of  the  schist  becomes  a 
granular  quartz  ;  and  when  hornblende  and  mica  are  added,  the 
dtered  rock  loses  its  stratification,  and.  passes  into  a  kind  of  granite. 
?he  limestone,  which  at  points  remote  from  the  granite  is  of  an 
eirthy  texture  and  blue  colour,  and  often  abounds  in  corals,  becomes 
a  white  granular  marble  near  the  granite,  sometimes  siliceous,  the 
granular  structure  extending  occasionally  upwards  of  400  yards  from 
tie  junction  ;  the  corals  being  for  the  most  part  obliterated,  though 
s)metimes  preserved,  even  in  the  white  marble.  Both  the  altered 

Fig.  705. 


Altered  zone  of  fossiliferous  slate  and  limestone  near  granite.    Christiania. 
The  arrows  indicate  the  dip,  and  the  straight  lines  the  strike,  of  the  beds. 

limestone  and  hardened  slate  contain  garnets  in  many  places,  also 
ores  of  iron,  lead,  and  copper,  with  some  silver.  These  alterations 
occur  equally,  whether  the  granite  invades  the  strata  in  a  line  pa- 
rallel to  the  general  strike  of  the  fossiliferous  beds,  or  in  a  line  at 

Q  Q  4 


600  ALTERATIONS   OF   STRATA.  [On.  XXXV. 

right  angles  to  their  strike,  as  will  be  seen  by  the  accompanying 
ground  plan.* 

The  indurated  and  ribboned  schists  above  mentioned  bear  a  strong 
resemblance  to  certain  shales  of  the  coal  found  at  Kussell's  Hall, 
near  Dudley,  where  coal-mines  have  been  on  fire  for  ages.  Beds  of 
shale  of  considerable  thickness,  lying  over  the  burning  coal,  have 
been  baked  and  hardened  so  as  to  acquire  a  flinty  fracture,  the  layers 
being  alternately  green  and  brick-coloured. 

The  granite  of  Cornwall,  in  like  manner,  sends  forth  veins  into  a 
coarse  argillaceous-schist,  provincially  termed  killas.  This  killas  is 
converted  into  hornblende-schist  near  the  contact  with  the  veins. 
These  appearances  are  well  seen  at  the  junction  of  the  granite  and 
killas,  in  St.  Michael's  Mount,  a  small  island  nearly  300  feet  high, 
situated  in  the  bay,  at  a  distance  of  about  three  miles  from  Pen- 
zance. 

The  granite  of  Dartmoor,  in  Devonshire,  says  Sir  H.  De  la  Beche, 
has  intruded  itself  into  the  slate  and  slaty  sandstone  called  grey  wacke, 
twisting  and  contorting  the  strata,  and  sending  veins  into  them. 
Hence  some  of  the  slate  rocks  have  become  "  micaceous ;  others  more 
indurated,  and  with  the  characters  of  mica-slate  and  gneiss ;  while 
others  again  appear  converted  into  a  hard-zoned  rock  strongly  im- 
pregnated with  felspar."  f 

We  learn  from  the  investigations  of  M.  Dufrenoy,  that  in  the 
eastern  Pyrenees  there  are  mountain  masses  of  granite  posterior  ir 
date  to  the  formations  called  lias  and  chalk  of  that  district,  and  thai 
these  fossiliferous  rocks  are  greatly  altered  in  texture,  and  ofter 
charged  with  iron-ore,  in  the  neighbourhood  of  the  granite.  Thui 
in  the  environs  of  St.  Martin,  near  St.  Paul  de  Fenouillet,  the  chalkj 
limestone  becomes  more  crystalline  and  saccharoid  as  it  approaches 
the  granite,  and  loses  all  trace  of  the  fossils  which  it  previously  con 
tained  in  abundance.  At  some  points,  also,  it  becomes  dolomitic 
and  filled  with  small  veins  of  carbonate  of  iron,  and  spots  of  rec 
iron-ore.  At  Rancie  the  lias  nearest  the  granite  is  not  only  fillec 
with  iron-ore,  but  charged  with  pyrites,  tremolite,  garnet,  and  a  ne^v 
mineral  somewhat  allied  to  felspar,  called,  from  the  place  in  th 
Pyrenees  where  it  occurs,  "  couzeranite." 

Now  the  alterations  above  described  as  superinduced  in  rocks  b} 
volcanic  dikes  and  granite  veins  prove  incontestably  that  powers 
exist  in  nature  capable  of  transforming  fossiliferous  into  crystalline 
strata — powers  capable  of  generating  in  them  a  new  mineral  charac 
ter,  similar  to,  nay,  often  absolutely  identical  with  that  of  gneiss 
mica-schist,  and  other  stratified  members  of  the  hypogene  series.    Th 
precise  nature  of  these  altering  causes,  which  may  provisionally  be 
termed  plutonic.  is  in  a  great  degree  obscure  and  doubtful ;   but 
their  reality  is  no  less  clear,  and  we  must  suppose  the  influence  o 
heat  to  be  in  some  way  connected  with  the  transmutation,  if,  for 
reasons  before  explained,  we  concede  the  igneous  origin  of  granite. 

*  Keilhau,  Gaea  Norvegica,  pp.61 — 63.  f  Geol.  Manual,  p.  479- 


CH.  XXXV.]  PLUTONIC  ACTION.  601 

The  experiments  of  Gregory  Watt,  in  fusing  rocks  in  the  labora- 
tory, and  allowing  them  to  consolidate  by  slow  cooling,  prove  dis- 
tinctly that  a  rock  need  not  be  perfectly  melted  in  order  that  a 
re-arrangement  of  its  component  particles  should  take  place,  and  a 
partial  crystallization  ensue.*  We  may  easily  suppose,  therefore, 
that  all  traces  of  shells  and  other  organic  remains  may  be  destroyed  ; 
and  that  new  chemical  combinations  may  arise,  without  the  mass 
being  so  fused  as  that  the  lines  of  stratification  should  be  wholly 
obliterated. 

We  must  not,  however,  imagine  that  heat  alone,  such  as  may  be 
applied  to  a  stone  in  the  open  air,  can  constitute  all  that  is  comprised 
in  plutonic  action.  We  know  that  volcanos  in  eruption  not  only  emit 
fluid  lava,  but  give  off  steam  and  other  heated  gases,  which  rush  out 
in  enormous  volume,  for  days,  weeks,  or  years  continuously,  and  are 
even  disengaged  from  lava  during  its  consolidation.  When  the  mate- 
rials of  granite,  therefore,  came  in  contact  with  the  fossiliferous  stra- 
tum in  the  bowels  of  the  earth  under  great  pressure,  the  contained 
gases  might  be  unable  to  escape ;  yet  when  brought  into  contact  with 
rocks,  they  might  pass  through  their  pores  with  greater  facility  than 
water  is  known  to  do  (p.  35.).  These  aeriform  fluids,  such  as  sulphu- 
retted hydrogen,  muriatic  acid,  and  carbonic  acid,  issue  in  many 
places  from  rents  in  rocks,  which  they  have  discoloured  and  corroded, 
softening  some  and  hardening  others.  If  the  rocks  are  charged  with 
water,  they  would  pass  through  more  readily  ;  for,  according  to  the 
experiments  of  Henry,  water,  under  an  hydrostatic  pressure  of 
96  feet,  will  absorb  three  times  as  much  carbonic  acid  gas  as  it  can 
under  the  ordinary  pressure  of  the  atmosphere.  Although  this  in- 
creased power  of  absorption  would  be  diminished  in  consequence  of 
the  higher  temperature  found  to  exist  as  we  descend  in  the  earth,  yet 
Professor  Bischoff  has  shown  that  the  heat  by  no  means  augments  in 
such  a  proportion  as  to  counteract  the  effect  of  augmented  pressure.f 
There  are  other  gases,  as  well  as  the  carbonic  acid,  which  water 
absorbs,  and  more  rapidly  in  proportion  to  the  amount  of  pressure. 
Now  even  the  most  compact  rocks  may  be  regarded,  before  they  have 
been  exposed  to  the  air  and  dried,  in  the  light  of  sponges  filled  with 
water  ;  and  it  is  conceivable  that  heated  gases  brought  into  contact 
with  them,  at  great  depths,  may  be  absorbed  readily,  and  transfused 
through  their  pores.  Although  the  gaseous  matter  first  absorbed 
would  soon  be  condensed,  and  part  with  its  heat,  yet  the  continual 
arrival  of  fresh  supplies  from  below  might,  in  the  course  of  ages, 
cause  the  temperature  of  the  water,  and  with  it  that  of  the  contain- 
ing rock,  to  be  materially  raised. 

M.  Fournet,  in  his  description  of  the  metalliferous  gneiss  near 
Clermont,  in  Auvergne,  states  that  all  the  minute  fissures  of  the  rock 
are  quite  saturated  with  free  carbonic  acid  gas ;  which  gas  rises 
plentifully  from  the  soil  there  and  in  many  parts  of  the  surrounding 

*  Phil.  Trans.,  1804.  t  Poggendorfs  Annalen,  No.xvi.,  2d 

series,  vol.  iii. 


602   ROCKS  ALTERED  BY  SUBTERRANEAN  GASES.  [Cn.  XXXV. 

country.  The  various  elements  of  the  gneiss,  with  the  exception  of 
the  quartz,  are  all  softened ;  and  new  combinations  of  the  acid  with 
lime,  iron,  and  manganese  are  continually  in  progress.* 

Another  illustration  of  the  power  of  subterranean  gases  is  afforded 
by  the  stufas  of  St.  Calogero,  situated  in  the  largest  of  the  Lipari 
Islands.  Here,  according  to  the  description  published  by  Hoffmann, 
horizontal  strata  of  tuff,  extending  for  4  miles  along  the  coast,  and 
forming  cliffs  more  than  200  feet  high,  have  been  discoloured  in 
various  places,  and  strangely  altered  by  the  "  all-penetrating  va- 
pours." Dark  clays  have  become  yellow,  or  often  snow-white  ;  or 
have  assumed  a  chequered  or  brecciated  appearance,  being  crossed 
with  ferruginous  red  stripes.  In  some  places  the  fumeroles  have 
been  found  by  analysis  to  consist  partly  of  sublimations  of  oxide  of 
iron ;  but  it  also  appears  that  veins  of  chalcedony  and  opal,  and 
others  of  fibrous  gypsum,  have  resulted  from  these  volcanic  exhala- 
tions, j" 

The  reader  may  also  refer  to  M.  Virlet's  account  of  the  corrosion 
of  hard,  flinty,  and  jaspideous  rocks  near  Corinth  by  the  prolonged 
agency  of  subterranean  gases  J  ;  and  to  Dr.  Daubeny's  description  of 
the  decomposition  of  trachytic  rocks  in  the  Solfatara,  near  Naples, 
by  sulphuretted  hydrogen  and  muriatic  acid  gases.  § 

Although  in  all  these  instances  we  can  only  study  the  phenomena 
as  exhibited  at  the  surface,  it  is  clear  that  the  gaseous  fluids  must 
have  made  their  way  through  the  whole  thickness  of  porous  or 
fissured  rocks,  which  intervene  between  the  subterranean  reservoirs 
of  gas  and  the  external  air.  The  extent,  therefore,  of  the  earth's 
crust  which  the  vapours  have  permeated  and  are  now  permeating 
may  be  thousands  of  fathoms  in  thickness,  and  their  heating  and 
modifying  influence  may  be  spread  throughout  the  whole  of  this 
solid  mass. 

We  learn  from  Professor  Bischoff  that  the  steam  of  a  hot  spring 
at  Aix-la-Chapelle,  although  its  temperature  is  only  from  133°  to 
167°  F.,  has  converted  the  surface  of  some  blocks  of  black  marble 
into  a  doughy  mass.  He  conceives,  therefore,  that  steam  in  the 
bowels  of  the  earth  having  a  temperature  equal  or  even  greater  than 
the  melting  point  of  lava,  and  having  an  elasticity  of  which  even 
Papin's  digester  can  give  but  a  faint  idea,  may  convert  rocks  into 
liquid  matter.  || 

The  above  observations  are  calculated  to  meet  some  of  the  ob- 
jections which  have  been  urged  against  the  metamorphic  theory  on 
the  ground  of  the  small  power  of  rocks  to  conduct  heat ;  for  it  is 
well  known  that  rocks,  when  dry  and  in  the  air,  differ  remarkably 
from  metals  in  this  respect.  It  has  been  asked  how  the  changes 

*  See  Principles,  Index,  "  Carbonated  de  la  Soc.  Geol.  de  France,  torn.  ii. 
Springs,"  &c.  p.  230. 

f  Hoffmann's  Liparischen  Inseln,  §  See  Princ.  of  Geol. ;  and  Daubeny's 
p.  38.  Leipzig,  1832.  Volcanos,  p.  167. 

$  See  Princ.  of  Geol.;  and  Bulletin  ||  Jam.  Ed.  New  Phil.  Journ.,No.  51. 

p.  43. 


CH.XXXV.]      ORIGIN   OF    METAMORPHIC    STRUCTURE.  603 

which  extend  merely  for  a  few  feet  from  the  contact  of  a  dike  could 
have  penetrated  through  mountain  masses  of  crystalline  strata 
several  miles  in  thickness.  Now  it  has  been  stated  that  the  plu- 
tonic  influence  of  the  syenite  of  Norway  has  sometimes  altered 
fossiliferous  strata  for  a  distance  of  a  quarter  of  a  mile,  both  in  the 
direction  of  their  dip  and  of  their  strike.  (See  fig.  705.  p.  599.) 
This  is  undoubtedly  an  extreme  case ;  but  is  it  not  far  more  philo- 
sophical to  suppose  that  this  influence  may,  under  favourable  cir- 
cumstances, affect  denser  masses,  than  to  invent  an  entirely  new 
cause  to  account  for  effects  merely  differing  in  quantity,  and  not  in 
kind  ?  The  metamorphic  theory  does  not  require  us  to  affirm  that 
some  contiguous  mass  of  granite  has  been  the  altering  power ;  but 
merely  that  an  action,  existing  in  the  interior  of  the  earth  at  an 
unknown  depth,  whether  thermal,  hydro -thermal,  electrical,  or 
other,  analogous  to  that  exerted  near  intruding  masses  of  granite, 
has,  in  the  course  of  vast  and  indefinite  periods,  and  when  rising 
perhaps  from  a  large  heated  surface,  reduced  strata  thousands  of 
yards  thick  to  a  state  of  semifusion,  so  that  on  cooling  they  have 
become  crystalline,  like  gneiss.  Granite  may  have  been  another 
result  of  the  same  action  in  a  higher  state  of  intensity,  by  which  a 
thorough  fusion  has  been  produced ;  and  in  this  manner  the  passage 
from  granite  into  gneiss  may  be  explained. 

In  considering,  then,  the  various  data  already  enumerated,  the 
forms  of  stratification  and  lamination  in  metamorphic  rocks,  their 
passage  on  the  one  hand  into  the  fossiliferous,  and  on  the  other  into 
the  plutonic  formations,  and  the  conversions  which  can  be  ascer- 
tained to  have  occurred  in  the  vicinity  of  granite,  we  may  conclude 
that  gneiss  and  mica-schist  may  be  nothing  more  than  altered 
micaceous  and  argillaceous  sandstones,  that  granular  quartz  may 
have  been  derived  from  siliceous  sandstone,  and  compact  quartz 
from  the  same  materials.  Clay-slate  may  be  altered  shale,  and 
granular  marble  may  have  originated  in  the  form  of  ordinary  lime- 
stone, replete  with  shells  and  corals,  which  have  since  been  obli- 
terated ;  and,  lastly,  calcareous  sands  and  marls  may  have  been 
changed  into  impure  crystalline  limestones. 

"  Hornblende-schist,"  says  Dr.  MacCulloch,  "  may  at  first  have 
been  mere  clay ;  for  clay  or  shale  is  found  altered  by  trap  into 
Lydian  stone,  a  substance  differing  from  hornblende-schist  almost 
solely  in  compactness  and  uniformity  of  texture."  *  "  In  Shetland," 
remarks  the  same  author,  "  argillaceous-schist  (or  clay-slate),  when 
in  contact  with  granite,  is  sometimes  converted  into  hornblende- 
schist,  the  schist  becoming  first  siliceous,  and  ultimately,  at  the 
contact,  hornblende-schist."  f 

The  anthracite  and  plumbago  associated  with  hypogene  rocks 
may  have  been  coal ;  for  not  only  is  coal  converted  into  anthracite 
in  the  vicinity  of  some  trap  dikes,  but  we  have  seen  that  a  like 
change  has  taken  place  generally  even  far  from  the  contact  of 

*  Syst.  of  Geol.  vol.  i.  p.  210.  f  Ibid.,  p.  211. 


604  ORIGIN   OF    METAMORPHIC    STRUCTURE.       [Cn.  XXXV. 

igneous  rocks,  in  the  disturbed  region  of  the  Appalachians.*  At 
Worcester,  in  the  state  of  Massachusetts,  45  miles  due  west  c.f 
Boston,  a  bed  of  plumbago  and  impure  anthracite  occurs,  inter- 
stratified  with  mica-schist.  It  is  about  2  feet  in  thickness,  and  has 
been  made  use  of  both  as  fuel,  and  in  the  manufacture  of  lead 
pencils.  At  the  distance  of  30  miles  from  the  plumbago,  there 
occurs,  on  the  borders  of  Rhode  Island,  an  impure  anthracite  in 
slates  containing  impressions  of  coal-plants  of  the  genera  Pecopteris, 
JVeuropteris,  Calamites,  &c.  This  anthracite  is  intermediate  in 
character  between  that  of  Pennsylvania  and  the  plumbago  of 
Worcester,  in  which  last  the  gaseous  or  volatile  matter  (hydrogen, 
oxygen,  and  nitrogen)  is  to  the  carbon  only  in  the  proportion  of 
3  per  cent.  After  traversing  the  country  in  various  directions,  I 
came  to  the  conclusion  that  the  carboniferous  shales  or  slates  with 
anthracite  and  plants,  which  in  Rhode  Island  often  pass  into  mica- 
schist,  have  at  Worcester  assumed  a  perfectly  crystalline  and  meta- 
morphic  texture ;  the  anthracite  having  been  nearly  transmuted  into 
that  state  of  pure  carbon  which  is  called  plumbago  or  graphite. | 

It  has  been  remarked  by  M.  Delesse  that  the  minerals  developed 
in  hypogene  limestone  vary  according  to  the  degree  of  metamor- 
phism  which  the  rock  has  undergone.  Thus,  for  example,  where 
the  structure  is  but  slightly  crystalline,  talc,  chlorite,  serpentine, 
andalusite,  and  kyanite  are  commonly  present ;  where  it  is  more 
highly  crystallized,  garnet,  hornblende,  Wollastonite,  dipyre,  Cou- 
zeranite,  and  some  others  appear ;  and,  lastly,  where  the  crystalliza- 
tion is  complete,  there  are  found,  in  addition  to  many  of  the  above 
minerals,  felspar,  especially  those  kinds  which  are  richest  in  alkali, 
together  with  mica.  The  same  author  observes  that,  as  calcareous 
deposits  usually  contain  some  aluminous  clay,  so  we  may  naturally 
expect  to  meet  with  silicates  of  alumina  in  crystalline  limestone  ; 
such  silicates,  accordingly,  are  frequent,  and  occasionally  even  pure 
alumina  crystallized  in  the  form  of  corundum.J 

Mr.  Dana  has  suggested  that  the  phosphoric  acid  of  phosphate  of 
lime,  and  the  fluor  of  fluor-spar,  so  often  met  with  in  crystalline 
limestones,  may  have  been  derived  from  the  remains  of  mollusca 
and  other  animals;  also  that  graphite  (which  is  pure  carbon  in  a 
crystalline  form,  with  or  without  admixture  of  alumina,  lime,  or 
iron)  may  have  been  derived  from  vegetable  remains  imbedded  in 
the  orignal  matrix. 

The  total  absence  of  any  trace  of  fossils  has  inclined  many  geo- 
logists to  attribute  the  origin  of  the  crystalline  strata  to  a  period 
antecedent  to  the  existence  of  organic  beings.  Admitting,  they  say, 
the  obliteration,  in  some  cases,  of  fossils  by  plutonic  action,  we  might 
still  expect  that  traces  of  them  would  oftener  occur  in  certain  ancient 
systems  of  slate,  in  which,  as  in  Cumberland,  some  conglomerates 

*  See  above,  pp.  392,  398.  \  Delesse,  Bulletin  Soc.  Geol.  France, 

f  See   Lyell,  Quart.    Geol.   Journ.,    2e  serie,  torn.  9.  p.  126.    1851. 
vol.  i.  p.  199. 


CH.  XXXV.]      OBJECTIONS   TO    METAMORPHIC    THEORY.  605 

occur.  But  in  urging  this  argument,  it  seems  to  have  been  forgotten 
that  there  are  stratified  formations  of  enormous  thickness,  and  of 
various  ages,  and  some  of  them  very  modern,  all  formed  after  the 
earth  had  become  the  abode  of  living  creatures,  which  are,  never- 
theless, in  certain  districts,  entirely  destitute  of  all  vestiges  of  or- 
ganic bodies.  In  some,  the  traces  of  fossils  may  have  been  effaced 
by  water  and  acids,  at  many  successive  periods ;  and  it  is  clear,  that, 
the  older  the  stratum,  the  greater  is  the  chance  of  its  being  nonfossi- 
liferous,  even  if  it  has  escaped  all  metamorphic  action. 

It  has  been  also  objected  to  t^e  metamorphic  theory,  that  the 
chemical  composition  of  the  secondary  strata  differs  essentially  from 
that  of  the  crystalline  schists,  into  which  they  are  supposed  to  be 
convertible.*  The  "  primary  "  schists,  it  is  said,  usually  contain  a 
considerable  proportion  of  potash  or  of  soda,  which  the  secondary 
clays,  shales,  and  slates  do  not,  these  last  being  the  result  of  the 
decomposition  of  felspathic  rocks,  from  which  the  alkaline  matter  has 
been  abstracted  during  the  process  of  decomposition.  But  this  rea- 
soning proceeds  on  insufficient  and  apparently  mistaken  data ;  for 
a  large  portion  of  what  is  usually  called  clay,  marl,  shale,  and  slate 
does  actually  contain  a  certain,  and  often  a  considerable,  proportion 
of  alkali ;  so  that  it  is  difficult,  in  many  countries,  to  obtain  clay  or 
shale  sufficiently  free  from  alkaline  ingredients  to  allow  of  their  being 
burnt  into  bricks  or  used  for  pottery. 

Thus  the  argillaceous  shales  and  slates  of  the  Old  Red  sandstone, 
in  Forfarshire  and  other  parts  of  Scotland,  are  so  much  charged  with 
alkali,  derived  from  triturated  felspar,  that,  instead  of  hardening  when 
exposed  to  fire,  they  sometimes  melt  into  a  glass.  They  contain  no 
lime,  but  appear  to  consist  of  extremely  minute  grains  of  the  various 
ingredients  of  granite,  which  are  distinctly  visible  in  the  coarser- 
grained  varieties,  and  in  almost  all  the  interposed  sandstones.  These 
laminated  clays  and  shales  might  certainly,  if  crystallized,  resemble 
in  composition  many  of  the  primary  strata. 

There  is  also  potash  in  fossil  vegetable  remains,  and  soda  in  the 
salts  by  which  strata  are  sometimes  so  largely  impregnated,  a!s  in 
Patagonia.  But  recent  analysis  may  be  said  to  have  settled  the 
point  at  issue,  by  demonstrating  that  the  carboniferous  strata  in 
England  f,  the  Upper  and  Lower  Silurian  in  East  Canada  J,  and  the 
clay-slates  (of  Cambrian  date  ?)  in  Norway  §,  all  contain  as  much 
alkali  as  is  generally  present  in  metamorphic  rocks. 

Another  objection  has  been  derived  from  the  alternation  of  highly 
crystalline  strata  with  others  having  a  less  crystalline  texture.  The 
heat,  it  is  said,  in  its  ascent  from  below,  must  have  traversed  the 
less  altered  schists  before  it  reached  a  higher  and  more  crystalline 
bed.  In  answer  to  this,  it  may  be  observed,  that  if  a  number  of 
strata  differing  greatly  in  composition  from  each  other  be  subjected 

*  Dr.   Boase,  Primary  Geology,   p.  J  Hunt,  Phil.  Mag.  4  ser.  vol.vii.p.237. 

319.  §  Kyersly,  Norsk,  Mag.  for  Naturvi- 

f  H.  Taylor,  Edin.  New,  Phil.  Journ.  denp.  vol.  viii.  p.  172. 
vol.  1.  1851,  p.  140. 


606  METAMORPHIC    THEORY.  [Cn.  XXXV. 

to  equal  quantities  of  heat,  there  is  every  probability  that  some  will 
be  more  fusible  than  others.  Some,  for  example,  will  contain  soda, 
potash,  lime,  or  some  other  ingredient  capable  of  acting  as  a  flux  ; 
while  others  may  be  destitute  of  the  same  elements,  and  so  refractory 
as  to  be  very  slightly  affected  by  a  degree  of  heat  capable  of  reducing 
others  to  semi-fusion.  Nor  should  it  be  forgotten  that,  as  a  general 
rule,  the  less  crystalline  rocks  do  really  occur  in  the  upper,  and  the 
more  crystalline  in  the  lower  part  of  each  metamorphic  series. 

Moreover,  metamorphism  must  often  begin  to  exert  its  force 
long  after  the  strata  have  assumed  a  vertical  position,  and  it  may 
then  act  locally  or  within  limited  areas,  and  will  be  as  likely  to 
affect  the  newer  as  the  older  beds.  As  an  illustration  of  such 
partial  conversion  into  gneiss  of  portions  of  a  highly  inclined  set 
of  beds,  I  may  cite  Sir  R.  Murchison's  memoir  on  the  structure 
of  the  Alps.  Slates  provincially  termed  "  flysch  "  (see  above  p.  231.), 
overlying  the  nummulite  limestone  of  Eocene  date,  and  comprising 
some  arenaceous  and  some  calcareous  layers,  are  seen  to  alternate 
several  times  with  bands  of  granitoid  rock,  answering  in  character 
to  gneiss.*  In  this  case  heat,  or  vapour,  or  water  at  an  intensely 
high  temperature  may  have  traversed  the  more  permeable  beds,  and 
altered  them  so  far  as  to  admit  of  an  internal  movement  and  re-ar- 
rangement of  the  molecules,  while  the  adjoining  strata  did  not  give 
passage  to  the  same  heat,  or  if  so,  remained  unchanged  because  they 
were  composed  of  less  fusible  materials.  Whatever  hypothesis  we 
adopt,  the  phenomena  establish  beyond  a  doubt  the  possibility  of 
the  development  of  the  metamorphic  structure  in  a  tertiary  deposit 
in  planes  parallel  to  those  of  stratification. 

Whether  such  parallelism  be  the  rule  or  the  exception  in  gneiss, 
mica- schist,  and  other  formations  of  the  same  family,  is  a  question 
which  I  shall  discuss  at  length  in  the  next  chapter. 

*  Geol.  Quart.  Journ.  vol.  v.  p.  211.     1848. 


GH.  XXXVI.]  METAMORPHIC   ROCKS.  607 


CHAPTER  XXXVI. 

Origin  of  the  metamorphic  rocks,  continued — Definition  of  joints,  slaty  cleavage 
and  foliation — Supposed  causes  of  these  structures — Mechanical  theory  of  cleav- 
age— Condensation  and  elongation  of  slate  rocks  by  lateral  pressure — Supposed 
combination  of  crystalline  and  mechanical  forces — Lamination  of  some  volcanic 
rocks  due  to  motion  —  Whether  the  foliation  of  the  crystalline  schists  be 
usually  parallel  with  the  original  planes  of  stratification — Examples  in  Norway 
and  Scotland — Foliation  in  homogeneous  rocks  may  coincide  with  planes  of 
cleavage,  and  in  uncleaved  rocks  with  those  of  stratification  —  Causes  of  irregu- 
larity in  the  planes  of  foliation. 

WE  have  already  seen  that  crystalline  forces  of  great  intensity  have 
frequently  acted  upon  sedimentary  and  fossiliferous  strata  long 
subsequently  to  their  consolidation,  and  we  may  next  inquire 
whether  the  component  minerals  of  the  altered  rocks  usually  arrange 
themselves  in  planes  parallel  to  the  original  planes  of  stratification, 
or  whether,  after  crystallization,  they  more  commonly  take  up  a 
different  position. 

In  order  to  estimate  fairly  the  merits  of  this  question,  we  must 
first  define  what  is  meant  by  the  terms  cleavage  and  foliation. 
There  are  four  distinct  forms  of  structure  exhibited  in  rocks, 
namely,  stratification,  joints,  slaty  cleavage,  and  foliation ;  and  all 
these  must  have  different  names,  even  though  there  be  cases  where 
it  is  impossible,  after  carefully  studying  the  appearances,  to  decide 
upon  the  class  to  which  they  belong. 

Professor  Sedgwick,  whose  essay  "  On  the  Structure  of  large 
Mineral  Masses"  first  cleared  the  way  towards  a  better  under- 
standing of  this  difficult  subject,  observes,  that  joints  are  distin- 
guishable from  lines  of  slaty  cleavage  in  this,  that  the  rock  inter- 
vening between  two  joints  has  no  tendency  to  cleave  in  a  direction 
parallel  to  the  planes  of  the  joints,  whereas  a  rock  is  capable  of 
indefinite  subdivision  in  the  direction  of  its  slaty  cleavage.  In  some 
cases  where  the  strata  are  curved,  the  planes  of  cleavage  are  still 
perfectly  parallel.  This  has  been  observed  in  the  slate  rocks  of 
part  of  Wales  (see  fig.  706.),  which  consist  of  a  hard  greenish  slate. 


Fig.  706. 


Parallel  planes  of  cleavage  intersecting  curved  strata.     (Sedgwick.) 

The  true  bedding  is  there  indicated  by  a  number  of  parallel  stripes, 
some  of  a  lighter  and  some  of  a  darker  colour  than  the  general  mass. 


608  JOINTED   STRUCTUEE  [Cn.  XXXVI. 

Such  stripes  are  found  to  be  parallel  to  the  true  planes  of  strati- 
fication, wherever  these  are  manifested  by  ripple-mark,  or  by  beds 
containing  peculiar  organic  remains.  Some  of  the  contorted  strata 
are  of  a  coarse  mechanical  structure,  alternating  with  fine-grained 
crystalline  chloritic  slates,  in  which  case  the  same  slaty  cleavage 
extends  through  the  coarser  and  finer  beds,  though  it  is  brought  out 
in  greater  perfection  in  proportion  as  the  materials  of  the  rock  are 
fine  and  homogeneous.  It  is  only  when  these  are  very  coarse  that 
the  cleavage  planes  entirely  vanish.  These  planes  are  usually  in- 
clined at  a  very  considerable  angle  to  the  planes  of  the  strata.  In 
the  Welsh  hills,  for  example,  the  average  angle  is  as  much  as  from 
30°  to  40°.  Sometimes  the  cleavage  planes  dip  towards  the  same 
point  of  the  compass  as  those  of  stratification,  but  more  frequently 
to  opposite  points.  It  may  be  stated  as  a  general  rule,  that  when 
beds  of  coarser  materials  alternate  with  those  composed  of  finer 
particles,  the  slaty  cleavage  is  either  entirely  confined  to  the  fine- 
grained rock,  -or  is  very  imperfectly  exhibited  in  that  of  coarser 
texture.  This  rule  holds,  whether  the  cleavage  is  parallel  to  the 
planes  of  stratification  or  not.* 

In  regard  to  joints,  they  are  natural  fissures  which  often  traverse 
rocks  in  straight  and  well-determined  lines.  They  afford  to  the 
quarryman,  as  Sir  R.  Murchison  observes,  when  speaking  of  the  phe- 
nomena, as  exhibited  in  Shropshire  and  the  neighbouring  counties, 
the  greatest  aid  in  the  extraction  of  blocks  of  stone ;  and,  if  a  suffi- 
cient number  cross  each  other,  the  whole  mass  of  rock  is  split  into 
symmetrical  blocks.  The  faces  of  the  joints  are  for  the  most  part 
smoother  and  more  regular  than  the  surfaces  of  true  strata.  The 
joints  are  straight-cut  chinks,  often  slightly  open,  often  passing,  not 
only  through  layers  of  successive  deposition,  but  also  through  balls 
of  limestone  or  other  matter  which  have  been  formed  by  concretion- 
ary action,  since  the  original  accumulation  of  the  strata.  Such 
joints,  therefore,  must  often  have  resulted  from  one  of  the  last  changes 
superinduced  upon  sedimentary  deposits. f 

In  the  annexed  diagram  (fig.  707.),  the  flat  surfaces  of  rock 
A,  B,  c,  represent  exposed  faces  of  joints,  to  which  the  walls  of  other 
joints,  J  J,  are  parallel,  s  s  are  the  lines  of  stratification  ;  D  D  are 
lines  of  slaty  cleavage,  which  intersect  the  rock  at  a  considerable 
angle  to  the  planes  of  stratification. 

In  the  Swiss  and  Savoy  Alps,  as  Mr.  Bakewell  has  remarked, 
enormous  masses  of  limestone  are  cut  through  so  regularly  by 
nearly  vertical  partings,  and  these  joints  are  often  so  much  more 
conspicuous  than  the  seams  of  stratification,  that  an  inexperienced 
observer  will  almost  inevitably  confound  them,  and  suppose  the 
strata  to  be  perpendicular  in  places  where  in  fact  they  are  almost 
horizontal.! 

Now  such  joints  are  supposed  to  be  analogous  to  the  partings 

*  Geol.  Trans.,  2d  series,  vol.  iii.  p.          f  Silurian  System,  p.  246. 
461.  J  Introduction  to  Geology,  chap.  iv. 


Cfi.  XXXVI.]  AND    CLEAVAGE.  609 

Fig.  707. 


Stratification,  joints,  and  cleavage. 
(From  Murchison's  Silurian  System,  p.  245.) 

which  separate  volcanic  and  plutonic  rocks  into  cuboidal  and  pris- 
matic masses.  On  a  small  scale  we  see  clay  and  starch  when  dry 
split  into  similar  shapes;  this  is  often  caused  by  simple  contrac- 
tion, whether  the  shrinking  be  due  to  the  evaporation  of  water, 
or  to  a  change  of  temperature.  It  is  well  known  that  many  sand- 
stones and  other  rocks  expand  by  the  application  of  moderate 
degrees  of  heat,  and  then  contract  again  on  cooling  ;  and  there  can 
be  no  doubt  that  large  portions  of  the  earth's  crust  have,  in  the 
course  of  past  ages,  been  subjected  again  and  again  to  very  different 
degrees  of  heat  and  cold.  These  alternations  of  temperature  have 
probably  contributed  largely  to  the  production  of  joints  in  rocks. 

In  some  countries,  as  in  Saxony,  where  masses  of  basalt  rest  on 
sandstone,  the  aqueous  rock  has  for  the  distance  of  several  feet  from 
the  point  of  junction  assumed  a  columnar  structure  similar  to  that 
of  the  trap.  In  like  manner  some  hearthstones,  after  exposure  to  the 
heat  of  a  furnace  without  being  melted,  have  become  prismatic. 
Certain  crystals  also  acquire  by  the  application  of  heat  a  new  in- 
ternal arrangement,  so  as  to  break  in  a  new  direction,  their  external 
form  remaining  unaltered. 

Professor  Sedgwick,  speaking  of  the  planes  of  slaty  cleavage, 
where  they  are  decidedly  distinct  from  those  of  sedimentary  de- 
position, declared  in  the  essay  before  alluded  to,  his  opinion  that  no 
retreat  of  parts,  no  contraction  in  the  dimensions  of  rocks  in  passing 
to  a  solid  state,  can  account  for  the  phenomenon.  He  accordingly 
referred  it  to  crystalline  or  polar  forces  acting  simultaneously,  and 
somewhat  uniformly,  in  given  directions,  on  large  masses  having  a 
homogeneous  composition. 

Sir  John  Herschel,  in  allusion  to  slaty  cleavage,  has  suggested, 
"  that  if  rocks  have  been  so  heated  as  to  allow  a  commencement  of 
crystallization, — that  is  to  say,  if  they  have  been  heated  to  a  point  at 
which  the  particles  can  begin  to  move  amongst  themselves,  or  at 
least  on  their  own  axes,  some  general  law  must  then  determine  the 
position  in  which  these  particles  will  rest  on  cooling.  Probably,  that 
position  will  have  some  relation  to  the  direction  in  which  the  heat 
escapes.  Nows  when  all,  or  a  majority  of  particles  of  the  same 

KK 


610  SLATY   CLEAVAGE.  [Cn.  XXXVI. 

nature  have  a  general  tendency  to  one  position,  that  must  of  course 
determine  a  cleavage-plane.  Thus  we  see  the  infinitesimal  crystals 
of  fresh  precipitated  sulphate  of  barytes,  and  some  other  such  bodies, 
arrange  themselves  alike  in  the  fluid  in  which  they  float ;  so  as, 
when  stirred,  all  to  glance  with  one  light,  and  give  the  appearance 
of  silky  filaments.  Some  sorts  of  soap,  in  which  insoluble  mar- 
garates  *  exist,  exhibit  the  same  phenomenon  when  mixed  with 
water ;  and  what  occurs  in  our  experiments  on  a  minute  scale  may 
occur  in  nature  on  a  great  one."! 

Professor  Phillips  has  remarked  that  in  some  slaty  rocks  the  form 
of  the  outline  of  fossil  shells  and  trilobites  has  been  much  changed 
by  distortion,  which  has  taken  place  in  a  longitudinal,  transverse,  or 
oblique  direction.  This  change,  he  adds,  seems  to  be  the  result  of 
a  "  creeping  movement "  of  the  particles  of  the  rock  along  the  planes 
of  cleavage,  its  direction  being  always  uniform  over  the  same  tract 
of  country,  and  its  amount  in  space  being  sometimes  measurable,  and 
being  as  much  as  a  quarter  or  even  half  an  inch.  The  hard  shells 
are  not  affected,  but  only  those  which  are  thin.J  Mr.  D.  Sharpe, 
following  up  the  same  line  of  inquiry,  came  to  the  conclusion,  that 
the  present  distorted  forms  of  the  shells  in  certain  British  slate 
rocks  may  be  accounted  for  by  supposing  that  the  rocks  in  which 
they  are  imbedded  have  undergone  compression  in  a  direction  per- 
pendicular to  the  planes  of  cleavage,  and  a  corresponding  expansion 
in  the  direction  of  the  dip  of  the  cleavage.  § 

More  recently  (July,  1853)  Mr.  Sorby  has  demonstrated  the  great 
extent  to  which  this  mechanical  theory  is  applicable  to  the  slate 
rocks  of  North  Wales  and  Devonshire  ||,  districts  where  the  amount 
of  change  in  dimensions  can  be  tested  and  measured  by  comparing 
the  different  effects  exerted  by  lateral  pressure  on  alternating 
beds  of  finer  and  coarser  materials.  Thus,  for  example,  in  the 
accompanying  figure  (fig.  708.)  it  will  be  seen  that  the  sandy  bed  df, 
which  has  offered  greater  resistance,  has  been  sharply  contorted, 
while  the  fine-grained  strata,  a,  b,  c,  have  remained  comparatively 
unbent.  The  points  d  and  f  in  the  stratum  d  f  must  have  been 
originally  four  times  as  far  apart  as  they  are  now.  They  have  been 
forced  so  much  nearer  to  each  other,  partly  by  bending,  and  partly 
by  becoming  elongated  in  the  direction  of  what  may  be  called  the 
longer  axes  of  their  contortions,  and  lastly,  to  a  certain  small  amount, 
by  condensation.  The  chief  result  has  obviously  been  due  to  the 
bending ;  but,  in  proof  of  elongation,  it  will  be  observed  that  the 
thickness  of  the  bed  df  is  now  about  four  times  greater  in  those  parts 
lying  in  the  main  direction  of  the  flexures  than  in  a  plane  perpen- 

*  Margaric  acid  is  an  oleaginous  acid,  \  Report,  Brit.  Asscc.,  Cork,   1843, 

formed  from  different  animal  and  vege-  Sect.  p.  60. 

table  fatty  substances.     Amargarateis  §  Quart.  Geol.  Journ.,  vol.  iii.  p.  87. 

a  compound  of  this  acid  with  soda,  po-  1847. 

tash,  or  some  other  base,  and  is  so  named  ||  On  the  Origin  of  Slaty  Cleavage,  by 

from  its  pearly  lustre.  H.  C.  Sorby,  Edinb.  New.  Phil.  Journ. 

f  Letter  to  the  author,  dated  Cape  of  1853,  vol.  Iv.  p.  137. 
Good  Hope,  Feb.  20.  1836. 


CH.  XXXVI.]        SLATE  ROCK   OF   NORTH  DEVON. 


611 


Fig.  708. 


dicular  to  them ;  and  the  same  bed 
exhibits  cleavage-planes  in  the 
direction  of  the  greatest  move- 
ment, although  they  are  much 
fewer  than  in  the  slaty  strata 
above  and  below. 

Above  the  sandy  bed  d  f,  the 
stratum  c  is  somewhat  disturbed, 
while  the  next  bed  b  is  much  less 
so,  and  a  not  at  all ;  yet  all  these 
beds,  c,  b,  and  a,  must  have  un- 
dergone an  equal  amount  of  pres- 
sure with  d,  the  points  a  and  g 
having  approximated  as  much  to- 
wards each  other  as  have  d  and/! 
The  same  phenomena  are  also  re- 
peated in  the  beds  below  d,  and 
might  have  been  shown,  had  the 
section  been  extended  downwards. 
Hence  it  appears  that  the  finer  beds 
have  been  squeezed  into  a  fourth 
of  the  space  they  previously  oc- 
cupied, partly  by  condensation,  or 
the  closer  packing  of  their  ulti- 
mate particles  (which  has  given 
rise  to  the  great  specific  gravity 
of  such  slates),  and  partly  by  elon- 
gation in  the  line  of  the  dip  of  the 
cleavage,  of  which  the  general  di- 
rection is  perpendicular  to  that  of 

£  SS^^i3StS&    the  pressure.     «  These  and  nume- 
d.f.  A^S^^SS^^m^    r°us  othei*  cases  in  North  Devon 

slate  with  less  perfect  cleavage.  are    analogous,"    SayS    Mr.    Sorby, 

"  to  what  would  occur  if  a  strip  of 

paper  were  included  in  a  mass  of  some  soft  plastic  material  which 
would  readily  change  its  dimensions.  If  the  whole  were  then  com- 
pressed in  the  direction  of  the  length  of  the  strip  of  paper,  it  would 
be  bent  and  puckered  up  into  contortions,  whilst  the  plastic  material 
would  readily  change  its  dimensions  without  undergoing  such  con- 
tortions ;  and  the  difference  in  distance  of  the  ends  of  the  paper,  as 
measured  in  a  direct  line  or  along  it,  would  indicate  the  change  in 
the  dimensions  of  the  plastic  material." 

The  student  will  readily  conceive  that,  when  the  shape  of  a  fossil 
or  of  a  crystal  of  some  mineral,  or  of  a  spheroidal  concretion,  has 
been  altered  by  lateral  pressure,  the  new  forms  which  they  assume 
respectively  will  vary  according  to  whether  they  have  yielded  in 
one  or  more  directions.  They  may  have  been  drawn  out  solely  in 
the  direction  of  the  dip  of  the  cleavage,  or  they  may  have  yielded 

KR  2 


(Drawn  by  H.  C.  Sorby.) 

Vertical   section  of  slate  rock  in  the  cliffs 
near  Ilfracombe,  North  Devon. 

Scale  one  inch  to  one  foot. 

a,  b,  c,  e.  Fine-grained  slates,  the  stratifi- 
cation being  shown  partly  by  lighter,  or 
dark 
gree 


612  CONDENSATION   OF   SLATE   KOCKS.      [Cn.  XXXVI. 

in  a  plane  perpendicular  to  that  dip,  or  they  may  have  undergone 
both  these  movements.  By  microscopic  examination  of  minute 
crystals,  and  by  other  observations  too  minute  to  be  detailed  here, 
Mr.  Sorby  comes  to  the  conclusion  that  the  absolute  condensation  of 
the  slate  rocks  amounts  upon  an  average  to  about  one  half  their 
original  volume.  This  must  have  resulted  chiefly  from  the  forcing 
of  the  particles  more  closely  together,  so  as  to  fill  up  the  spaces 
left  between  them,  when  they  only  touched  each  other.  The  rest  of 
the  change  has  been  due  to  elongation  which  has  produced  slaty 
cleavage. 

Most  of  the  scales  of  mica  occurring  in  certain  slates  examined  by 
Mr.  Sorby  lie  in  the  plane  of  cleavage ;  whereas  in  a  similar  rock 
not  exhibiting  cleavagq  they  lie  with  their  longer  axes  in  all  direc- 
tions. May  not  their  position  in  the  slates  have  been  determined 
by  the  movement  of  elongation  before  alluded  to?  To  illustrate 
this  theory  some  scales  of  oxide  of  iron  were  mixed  with  soft 
pipe-clay  in  such  a  manner  that  they  inclined  in  all  directions. 
The  dimensions  of  the  mass  were  then  changed  artificially  to  a 
similar  extent  to  what  has  occurred  in  slate-rocks,  and  the  pipe-clay 
was  then  dried  and  baked.  When  it  was  afterwards  rubbed  to  a 
flat  surface  perpendicular  to  the  pressure  and  in  the  line  of  elon- 
gation, or  in  a  plane  corresponding  to  that  of  the  dip  of  cleavage, 
the  particles  were  found  to  have  become  arranged  in  the  same 
manner  as  in  natural  slates,  and  the  mass  admitted  of  easy  fracture 
into  thin  flat  pieces  in  the  plane  alluded  to,  whereas  it  would  not 
yield  in  that  perpendicular  to  the  cleavage.* 

This  experiment  may  lend  countenance  to  the  opinion  that  the 
lamination  of  basalt  and  trachyte,  and  even  of  some  kinds  of  gneiss, 
and  the  grain  of  certain  granites,  may  all  have  been  determined  by  a 
mechanical  cause,  a  movement  having  taken  place  after  the  de- 
velopment of  crystals  in  the  pasty-mass. 

Mr.  Scrope,  in  his  description  of  the  Ponza  Islands,  ascribed  "  the 
zoned  structure  of  the  Hungarian  perlite  (a  semi-vitreous  trachyte) 
to  its  having  subsided,  in  obedience  to  the  impulse  of  its  own 
gravity,  down  a  slightly  inclined  plane,  while  possessed  of  an  im- 
perfect fluidity.  In  the  islands  of  Ponza  and  Palmarola,  the  direc- 
tion of  the  zones  is  more  frequently  vertical  than  horizontal,  because 
the  mass  was  impelled  from  below  upwards."']'  In  like  manner, 
Mr.  Darwin  attributes  the  lamination  and  fissile  structure  of  volcanic 
rocks  of  the  trachytic  series,  including  some  obsidians  in  Ascension, 
Mexico,  and  elsewhere,  to  their  having  moved  when  liquid  in  the 
direction  of  the  laminae.  The  zones  consist  sometimes  of  layers  of 
air-cells  drawn  out  and  lengthened  in  the  supposed  direction  of  the 
moving  mass.  He  compares  this  division  into  parallel  zones,  thus 
caused  by  the  stretching  of  a  pasty  mass  as  it  flowed  slowly 
onwards,  to  the  zoned  or  ribboned  structure  of  ice,  which  Professor 

*  Sorby,  as  cited  above,  p.  610,  note.         f  Geol.  Trans.  2d  ser.  vol.  ii.  p.  227. 


CH.  XXXVI.]        FOLIATION   OF   CRYSTALLINE   ROCKS.  613 

James  Forbes  has  so  ably  explained,  showing  that  it  is  due  to  the 
fissuring  of  a  viscous  body  in  motion.* 

Whatever  be  the  cause,  the  result,  observes  Darwin,  is  well 
worthy  the  attention  of  geologists;  for  in  a  volcanic  rock  of  the 
trachytic  series  in  Ascension  layers  are  seen  often  of  extreme 
tenuity,  even  as  thin  as  hairs,  and  of  different  colqurs,  alternating 
again  and  again,  some  of  them  composed  of  crystals  of  quartz  and 
diopside  (a  kind  of  augite),  others  of  black  augitic  specks  with 
granules  of  oxide  of  iron,  and  lastly,  others  of  crystalline  felspar. 
It  is  supposed  in  this  case  that  the  crystallizing  force  acted  more 
freely  in  the  directiori  of  the  planes  of  cleavage,  produced  when  the 
pasty  mass  was  stretched,  whether  because  confined  vapours  were 
enabled  to  spread  themselves  through  the  minute  fissures,  or  because 
the  ultimate  molecules  had  more  freedom  of  motion  along  the  planes 
of  less  tension,  or  for  some  other  reasons  not  yet  understood. 

After  studying,  in  1835,  the  crystalline  rocks  of  South  America, 
Mr.  Darwin  proposed  the  term  foliation  for  the  lamina  or  plates 
into  which  gneiss,  mica-schist,  and  other  crystalline  rocks  are 
divided.  Cleavage,  he  observes,  may  be  applied  to  those  divisional 
planes  which  render  a  rock  fissile,  although  it  may  appear  to  the 
eye  quite  or  nearly  homogeneous.  Foliation  may  be  used  for  those 
alternating  layers  or  plates  of  different  mineralogical  nature  of 
which  gneiss  and  other  metamorphic  schists  are  composed.  The 
cleavage  planes  of  the  clay-slate  in  Terra  del  Fuego  and  Chili 
preserve  a  uniform  strike  for  hundreds  of  miles  in  regions  where 
these  planes  are  quite  distinct  from  stratification.  In  the  same 
country  the  planes  of  foliation  of  the  mica-schist  and  gneiss  are 
parallel  to  the  cleavage  of  the  clay-slate.  Hence,  we  are  tempted,  at 
first  sight,  to  infer  that  some  common  cause  or  process,  and  that  cause 
not  connected  with  sedimentary  deposition,  has  impressed  cleavage  on 
the  one  set  of  rocks  and  foliation  on  the  other.  But  such  an  infer- 
ence can  only  be  legitimately  drawn  in  those  rare  cases  where  we 
are  able,  by  a  continuous  section,  to  prove  that  not  only  the  strike,  but 
the  dip  of  the  slaty  cleavage  on  the  one  hand,  and  of  the  foliation  on 
the  other,  precisely  coincide ;  the  cleavage  at  the  same  time  not  being 
parallel  to  the  stratification  in  the  slate  rock.  In  some  examples 
cited  by  Mr.  Darwin,  in  Terra  del  Fuego,  the  Chonos  Islands, 
and  La  Plata,  this  uniformity  of  dip  seems  to  have  been  traced  in  a 
manner  as  satisfactory  as  the  nature  of  such  evidence  will  allow. 
But  we  must  be  on  our  guard  against  a  source  of  deception  which 
may  mislead  us  in  this  chain  of  reasoning.  We  are  informed  that 
in  South  America,  as  in  other  countries,  the  strike  of  the  cleavage 
in  clay-slate  conforms  to  the  axis  of  elevation  of  the  rocks  in  the 
same  districts.  Hence  it  must  follow  that  the  folia  of  gneiss,  mica- 
schist,  limestone,  and  other  crystalline  rocks,  even  if  they  strictly 
coincide  with  the  planes  of  original  stratification,  will  run  in  the 


*  Darwin,  Volcanic  Islands,  pp.  69,  70. 

Rll   3 


614  FOLIATION'   AND   CLEAVAGE  [Cn.  XXXVI. 

same  direction  as  the  strike  of  the  slaty  cleavage  ;  for  the  true 
strata  always  dip  at  right  angles  to  the  axis  of  elevation,  and  are 
parallel  to  it  in  their  strike.  No  argument,  therefore,  can  be  drawn 
in  favour  of  a  common  origin  from  uniformity  of  strike  in  the  slaty 
and  foliated  rocks ;  for  we  require,  in  addition,  coincidence  of  dip ; 
and  such  is  the^  variability  of  the  dip  both  of  the  slates  and  folia  as 
to  render  this  kind  of  proof  very  difficult  to  obtain. 

That  the  foliation  of  the  crystalline  schists  in  Norway  accords  very 
generally  with  the  planes  of  original  stratification  is  a  conclusion 
long  since  espoused  by  Keilhau.*  Numerous  observations  made  by 
Mr.  David  Forbes  in  the  same  country  (the  best  probably  in  Europe 
for  studying  such  phenomena  on  a  grand  scale)  confirm  Keilhau's 
opinion ;  for  the  dip  of  the  Silurian  and  fossiliferous  strata  where 
they  pass  into  the  metamorphic  agrees  with  the  foliation  of  the 
contiguous  gneiss,  mica-schist,  and  crystalline  limestone.  So  also 
in  Scotland  Mr.  D.  Forbes  has  pointed  out  a  striking  case  where 
the  foliation  is  identical  with  the  lines  of  stratification  in  rocks  well 
seen  near  Crianlorich  on  the  road  to  Tyndrum,  about  8  miles  from 
Inverarnon  in  Perthshire.  There  is  in  that  locality  a  blue  lime- 
stone foliated  by  the  intercalation  of  small  plates  of  white  mica,  so 
that  the  rock  is  often  scarcely  distinguishable  in  aspect  from  gneiss 
or  mica-schist.  The  stratification  is  shown  by  the  large  beds  and 
coloured  bands  of  limestone  all  dipping,  like  the  folia,  at  an  angle  of 
32  degrees  N.  E.f 

In  stratified  formations  of  every  age  we  see  layers  of  siliceous 
sand  with  or  without  mica,  alternating  with  clay,  with  fragments 
of  shells  or  corals,  or  with  seams  of  vegetable  matter,  and  we  should 
expect  the  mutual  attraction  of  like  particles  to  favour  the  crystal- 
lization of  the  quartz,  or  mica,  or  felspar,  or  carbonate  of  lime,  along 
the  planes  of  original  deposition,  rather  than  in  planes  placed  at 
angles  of  20  or  40  degrees  to  those  of  stratification. 

In  Patagonia,  a  series  of  thin  sedimentary  layers  of  tuff  were 
observed  by  Mr.  Darwin  to  have  become  porphyritic,  first  where 
least  altered,  by  a  process  of  aggregation,  small  patches  of  clay 
appearing  to  be  shortened  into  almond-shaped  concretions,  which  in 
those  places  where  they  were  more  changed  had  become  crystals  of 
felspar,  having  their  longer  axes  parallel  to  each  other.  In  other 
associated  strata,  grains  of  quartz  had  in  like  manner  aggregated 
into  nodules  of  crystalline  quartz.  :f 

May  we  not,  then,  presume  that  in  rocks  where  no  cleavage  has 
intervened,  foliation  and  the  planes  of  stratification  will  usually 
coincide,  as  in  all  cases  where  cleavage  happens  (as  in  the  writing- 
slates  of  the  Niesen  on  the  Lake  of  Thun  in  Switzerland,  containing 
fucoids)  to  agree  with  the  original  planes  of  sedimentary  deposition  ? 
Mr.  Darwin  conceives  that  "  foliation  may  be  the  extreme  result  of 

*  Norske  Mag.  Naturvidsk.,  vol.  i.  f  Memoir  read  before  the  Geol.  Soc., 
p.  71.  London,  Jan.  31.  1855. 

J  South  America,  p.  149. 


CH.  XXXVI. ]      OF  CRYSTALLINE  ROCKS.  615 

the  process  of  which  cleavage  is  the  first  effect ; "  or,  at  any  rate, 
that  the  crystalline  force  may  have  been  most  energetic  in  the 
direction  of  cleavage.  As  bearing  on  this  view,  he  says,  "  I  was 
particularly  struck  in  the  eastern  parts  of  Terra  del  Fuego  with  the 
fact  that  the  fine  laminae  of  clay-slate,  where  they  cut  straight 
through  the  bands  of  stratification,  and  therefore  indisputably  true 
cleavage-planes,  differ  slightly  from  one  another  in  their  greyish 
and  greenish  tints  of  colour,  as  also  in  their  compactness,  and  in 
some  laminae  having  a  more  jaspery  appearance  than  others.  This 
fact  shows  that  the  same  cause  which  has  produced  the  highly 
fissile  structure  has  altered  in  a  slight  degree  the  mineralogical 
character  of  the  rock  in  the  same  planes."*  As  one  step  farther 
towards  tracing  a  passage  from  planes  of  cleavage  to  those  of  folia- 
tion, Professor  Sedgwick  observes  that  in  North  Wales  the  surfaces 
of  slates  are  sometimes  coated  over  with  chlorite,  "  the  crystals  of 
which  have  not  only  defined  the  cleavage  planes  but  struck  through 
the  whole  mass  of  the  rock."  f  So  also,  says  Mr.  Darwin,  in  some 
places  in  South  America  crystals  of  epidote  and  of  mica  coat  the 
planes  of  cleavage. 

Mr.  D.  Sharpe  inferred  from  observations  made  by  him  in  the 
Highlands  of  Scotland,  in  1851,  that  the  foliation  of  the  gneiss  and 
mica-schist  are  upon  the  whole  parallel  to  one  another,  but  have  no 
connection  with  any  original  planes  of  stratification  ;  and  he  also 
conceives  that  the  planes  both  of  cleavage  and  foliation  in  the 
Grampians  and  in  the  region  of  Mont  Blanc  in  Switzerland  (which 
last  he  examined  in  1854)  are  parts  of  great  curves  or  anticlinal 
axes  of  considerable  regularity.^  In  like  manner  in  South  America 
the  cleavage  planes  of  the  clay-slate  had  been  suspected  by 
Mr.  Darwin,  notwithstanding  their  varying  and  opposite  dips,  to 
be  parts  of  large  curves  or  foldings,  having  their  summits  cut  off 
and  worn  down.§ 

There  seems  to  be  no  difficulty  in  imagining  that  in  rocks  of 
homogeneous  composition  the  foliation  may  take  place  along  planes 
previously  caused  by  the  elongation  of  the  materials  along  the  dip 
of  the  cleavage ;  for  experienced  geologists  have  been  at  a  loss  to 
decide  in  many  countries  which  of  two  sets  of  divisional  planes  were 
referable  to  cleavage,  and  which  to  stratification ;  and  after  much 
doubt,  have  discovered  that  they  had  at  first  mistaken  the  lines  of 
cleavage  for  those  of  deposition,  because  the  former  were  by  far  the 
most  marked  of  the  two.  Now  if  such  slaty  masses  should  become 
highly  crystalline,  and  be  converted  into  gneiss,  hornblende-schist, 
or  any  other  member  of  the  hypogene  class,  the  cleavage  planes 
would  be  more  likely  to  remain  visible  than  those  of  stratification. 
Professor  Henslow  had  noticed,  so  long  ago  as  the  year  1821,  that 

*  Geol.  Observ.  on  South  America,  J  D.  Sharpe,  Phil.  Trans.,  1852,  and 
p.  155.  GeoL  Quart.  Journ.,  no,  41.  1855. 

f  Sedgwick,   Geol     Trans.    2d  ser.          §  Darwin,  S.  America,  p.  155. 
voL  iii.  p  471. 

BE  4 


616  IRREGULAEITIES   IN   FOLIATION.        [Cn.  XXXVI. 

the  lamination  of  the  chloritic  and  other  crystalline  schists  in 
Anglesea  was  approximately  in  the  planes  of  bedding ;  and  Pro- 
fessor Ramsay,  in  1841,  observed  the  same  in  regard  to  the  gneiss 
and  mica-schist  of  Arran.  The  last-cited  geologist  says,  in  reference 
to  Anglesea,  that  the  metamorphism  probably  took  place  when  the 
Lower  Silurian  volcanos  were  in  activity,  and  therefore  long  before 
the  cleavage  of  the  Welsh  rocks;  for  the  cleavage  of  the  latter 
affects  in  common  the  Lower  Silurian  and  the  Cambrian  strata.  In 
the  same  memoir  he  adds,  when  referring  to  Mr.  Darwin's  theory  of 
foliation,  "  that  if  the  rocks  be  uncleaved  when  metamorphism 
occurs,  the  foliation  planes  will  be  apt  to  coincide  with  those  of 
bedding  ;  but  if  intense  cleavage  has  preceded,  then  we  may  expect 
that  the  planes  of  foliation  will  lie  in  the  planes  of  cleavage."* 

From  what  I  have  myself  seen  in  the  Grampians,  both  in  Forfar- 
shire  and  Perthshire,  I  have  always  concluded  that  Macculloch  was 
correct  in  the  opinion  that  gneiss  and  mica-schist  may  be  considered 
as  stratified  rocks,  and  that  certain  beds  of  pure  quartz,  one  or  two 
feet  thick,  which  run  for  miles  in  the  strike  of  their  foliation,  as  well 
as  the  intercalation  of  masses  of  limestone,  and  of  chloritic,  acti- 
nolitic,  and  hornblende  schists,  all  indicate  the  planes  of  original 
stratification.  At  the  same  time,  I  fully  admit  that  the  alternate 
layers  of  quartz,  or  of  mica  and  quartz,  of  felspar,  or  of  mica  and 
felspar,  or  of  carbonate  of  lime,  are  more  distinct,  in  certain  meta- 
morphic  rocks,  than  the  ingredients  composing  alternate  layers  in 
most  sedimentary  deposits,  so  that  similar  particles  must  be  supposed 
to  have  exerted  a  molecular  attraction  for  each  other,  and  to  have 
congregated  together  in  layers  more  distinct  in  mineral  composition 
than  before  they  were  crystallized. 

We  have  seen  how  much  the  original  planes  of  stratification  may 
be  interfered  with  or  even  obliterated  by  concretionary  action  in 
deposits  still  retaining  their  fossils,  as  in  the  case  of  the  magnesian 
limestone  (see  p.  37.).  Hence  we  must  expect  to  be  frequently 
baffled  when  we  attempt  to  decide  whether  the  foliation  does  or 
does  not  accord  with  that  arrangement  which  gravitation,  combined 
with  current-action,  imparted  to  a  deposit  from  water.  Moreover, 
when  we  look  for  stratification  in  crystalline  rocks,  we  must  be  on 
our  guard  not  to  expect  too  much  regularity.  The  occurrence  of 
wedge-shaped  masses,  such  as  belong  to  coarse  sand  and  pebbles, — 
diagonal  lamination  (seep.  16.), — ripple-mark, — unconformable  stra- 
tification (p.  61.),  —  the  fantastic  folds  produced  by  lateral  pressure, 
— faults  of  various  width,  —  intrusive  dikes  of  trap, — organic  bodies 
of  diversified  shapes,  —  and  other  causes  of  unevenness  in  the  planes 
of  deposition,  both  on  the  small  and  on  the  large  scale,  will  interfere 
with  parallelism.  If  complex  and  enigmatical  appearances  did  not 
present  themselves,  it  would  be  a  serious  objection  to  the  meta- 
morphic  theory. 

In  the  accompanying  diagram  I  have  represented  carefully  the 

*  Geol.  Quart.  Joum.,  1853,  vol.  ix.  p.  172. 


Cir.  XXXVI.]  LAMINATION   OF   CLAY-SLATE. 


617 


Fig.  709. 


lamination  of  a  coarse  argilla- 
ceous schist  which  I  examined 
in  1830  in  the  Pyrenees.  In 
part  it  approaches  in  character 
to  a  green  and  blue  roofing-slate, 
while  part  is  extremely  quartzose, 
the  whole  mass  passing  down- 
wards into  micaceous  schist.  The 
vertical  section  here  exhibited  is 
about  3  feet  in  height,  and  the 

Lamination  of  clay-slate,  Montagne  de  Seguinat,     layers  are  Sometimes  SO  thin  that 
near  Gavarnie,  in  the  Pyrenees. 

fitty  may  be  counted  in  the 
thickness  of  an  inch.  Some  of  them  consist  of  pure  quartz. 

There  is  a  resemblance  in  such  cases  to  the  diagonal  lamination 
which  we  see  in  sedimentary  rocks,  even  though  the  layers  of  quartz 
and  of  mica,  or  of  felspar  and  other  minerals  may  be  more  distinct  in 
alternating  folia  than  they  were  originally. 

M.  Elie  de  Beaumont,  while  he  regards  the  greater  part  of  the 
gneiss  and  mica-schist  of  the  Alps  as  sedimentary  strata  altered  by 
plutonic  action,  still  conceives  that  some  of  the  Alpine  gneiss  may 
have  been  erupted,  or,  in  other  words,  may  be  granite  drawn  out 
into  parallel  laminse  in  the  manner  of  trachyte  as  above  alluded  to.* 

If  the  mass  were  squeezed  and  elongated  in  a  certain  direction 
after  crystals  of  mica,  talc,  or  other  scaly  minerals  were  developed, 
these  may  perhaps  have  arranged  themselves  in  planes  parallel  to 
those  of  movement,  and  a  similar  process  may  account  for  what  the 
quarrymen  call  "  the  grain  "  in  some  granites,  or  a  tendency  to  split 
in  one  direction  more  freely  than  in  another.  But,  as  a  general  rule, 
the  fusion  of  the  crystalline  schists  does  not  appear  to  have  gone  so 
far  as  to  allow  of  motion  analogous  to  that  of  lava  or  granite,  and 
for  this  reason  rocks  of  this  class  do  not  send  veins  into  surrounding 
rocks.  In  the  next  chapter  we  may  inquire  at  how  many  distinct 
periods  the  hypogene  or  metamorphic  schists  can  be  proved  to  have 
originated,  and  why  for  so  long  a  time  the  earlier  geologists  regarded 
them  as  entitled  to  the  name  of  "  primitive." 


*  Bulletin  Soc.  Geol.  de  France,  2e  ser.  vol.  iv.  p.  1301. 


618  AGE  OF   METAMORPHIC  ROCKS.       [Cn.  XXXVII. 


CHAPTER  XXXVII. 

ON   THE   DIFFERENT   AGES   OF    THE   METAMORPHIC   ROCKS. 

Age  of  each  set  of  metamorphic  strata  twofold  —  Test  of  age  by  fossils  and  mineral 
character  not  available  — Test  by  superposition  ambiguous  —  Conversion  of  dense 
masses  of  fossiliferous  strata  into  metamorphic  rocks — Limestone  and  shale  of 
Carrara — Metamorphic  strata  of  older  date  than  the  Cambrian  rocks — Others 
of  Lower  Silurian  origin  —  Others  of  the  Jurassic  and  Eocene  periods  in  the 
Alps  of  Switzerland  and  Savoy — Why  scarcely  any  of  the  visible  crystalline 
strata  are  very  modern  —  Order  of  succession  in  metamorphic  rocks  —  Uni- 
formity of  mineral  character  —  Why  the  metamorphic  strata  are  less  calcareous 
than  the  fossilferous. 

ACCORDING  to  the  theory  adopted  in  the  last  chapter,  the  age  of  each 
set  of  metamorphic  strata  is  twofold,  —  they  have  been  deposited  at 
one  period,  they  have  become  crystalline  at  another.  We  can  rarely 
hope  to  define  with  exactness  the  date  of  both  these  periods,  the 
fossils  having  been  destroyed  by  plutonic  action,  and  the  mineral 
characters  being  the  same,  whatever  the  age.  Superposition  itself 
is  an  ambiguous  test,  especially  when  we  desire  to  determine  the 
period  of  crystallization.  Suppose,  for  example,  we  are  convinced 
that  certain  metamorphic  strata  in  the  Alps,  which  are  covered  by 
cretaceous  beds,  are  altered  lias ;  this  lias  may  have  assumed  its 
crystalline  texture  in  the  cretaceous  or  in  some  tertiary  period,  the 
Eocene  for  example.  If  in  the  latter,  it  should  be  called  Eocene 
when  regarded  as  a  metamorphic  rock,  although  it  be  liassic  when 
considered  in  reference  to  the  era  of  its  deposition.  According  to  this 
view,  the  superposition  of  chalk  does  not  prevent  the  subjacent 
metamorphic  rock  from  being  Eocene. 

When  discussing  the  ages  of  the  plutonic  rocks,  we  have  seen  that 
examples  occur  of  various  primary,  secondary,  and  tertiary  deposits 
converted  into  metamorphic  strata,  near  their  contact  with  granite. 
There  can  be  no  doubt  in  these  cases  that  strata,  once  composed  of 
mud,  sand,  and  gravel,  or  of  clay,  marl,  and  shelly  limestone,  have 
for  the  distance  of  several  yards,  and  in  some  instances  several 
hundred  feet,  been  turned  into  gneiss,  mica-schist,  hornblende-schist, 
chlorite-schist,  quartz  rock,  statuary  marble,  and  the  rest.  (See  the 
two  preceding  Chapters.) 

But  when  the  metamorphic  action  has  operated  on  a  grander  scale, 
it  tends  entirely  to  destroy  all  monuments  of  the  date  of  its  develop- 
ment. It  may  be  easy  to  prove  the  identity  of  two  different  parts  of 
the  same  stratum ;  one,  where  the  rock  has  been  in  contact  with  a 
volcanic  or  plutonic  mass,  and  has  been  changed  into  marble  or 


CH.  XXXVII.]  NORTHERN   APENNINES.  619 

hornblende-schist,  and  another  not  far  distant,  where  the  same  bed 
remains  unaltered  and  fossiliferous ;  but  when  we  have  to  compare 
two  portions  of  a  mountain  chain  —  the  one  metamorphic,  and  the 
other  unaltered — all  the  labour  and  skill  of  the  most  practised  ob- 
servers are  required,  and  may  sometimes  be  at  fault.  I  shall  men- 
tion one  or  two  examples  of  alteration  on  a  grand  scale,  in  order  to 
explain  to  the  student  the  kind  of  reasoning  by  which  we  are  led  to 
infer  that  dense  masses  of  fossiliferous  strata  have  been  converted 
into  crystalline  rocks. 

Northern  Apennines — Carrara.  —  The  celebrated  marble  of  Car- 
rara, used  in  sculpture,  was  once  regarded  as  a  type  of  primitive 
limestone.  It  abounds  in  the  mountains  of  Massa  Carrara,  or  the 
"  Apuan  Alps,"  as  they  have  been  called,  the  highest  peaks  of  which 
are  nearly  6000  feet  high.  Its  great  antiquity  was  inferred  from  its 
mineral  texture,  from  the  absence  of  fossils,  and  its  passage  down- 
wards into  talc-schist  and  garnetiferous  mica-schist;  these  rocks 
again  graduating  downwards  into  gneiss,  which  is  penetrated,  at 
Forno,  by  granite  veins.  Now  the  researches  of  MM.  Savi,  Boue, 
Pareto,  Guidoni,  De  la  Beche,  Hoffmann,  and  Pilla  have  demon- 
strated that  this  marble,  once  supposed  to  be  formed  before  the  ex- 
istence of  organic  beings,  is,  in  fact,  an  altered  limestone  of  the  Oolitic 
period,  and  the  underlying  crystalline  schists  are  secondary  sand- 
stones and  shales,  modified  by  plutonic  action.  In  order  to  establish 
these  conclusions,  it  was  first  pointed  out,  that  the  calcareous  rocks 
bordering  the  Gulf  of  Spezia,  and  abounding  in  Oolitic  fossils, 
assume  a  texture  like  that  of  Carrara  marble,  in  proportion  as  they 
are  more  and  more  invaded  by  certain  trappean  and  plutonic  rocks, 
such  as  a  diorite,  euphotide,  serpentine,  and  granite,  occurring  in 
the  same  country. 

It  was  then  observed  that,  in  places  where  the  secondary  forma- 
tions are  unaltered,  the  uppermost  consist  of  common  Apennine 
limestone  with  nodules  of  flint,  below  which  are  shales,  and  at  the 
base  of  all,  argillaceous  and  siliceous  sandstones.  In  the  limestone 
fossils  are  frequent,  but  very  rare  in  the  underlying  shale  and  sand- 
stone. Then  a  gradation  was  traced  laterally  from  these  rocks  into 
another  and  corresponding  series,  which  is  completely  metamorphic  ; 
for  at  the  top  of  this  we  find  a  white  granular  marble,  wholly  devoid 
of  fossils,  and  almost  without  stratification,  in  which  there  are  no 
nodules  of  flint,  but  in  its  place  siliceous  matter  disseminated 
through  the  mass  in  the  form  of  prisms  of  quartz.  Below  this,  and 
in  place  of  the  shales,  are  talc-schists,  jasper,  and  hornstone ;  and  at 
the  bottom,  instead  of  the  siliceous  and  argillaceous  sandstones,  are 
quartzite  and  gneiss.*  Had  these  secondary  strata  of  the  Apennines 
undergone  universally  as  great  an  amount  of  transmutation,  it  would 
have  been  impossible  to  form  a  conjecture  respecting  their  true  age  ; 
and  then,  according  to  the  method  of  classification  adopted  by  the 

*  See  notices  of  Savi,  Hoffmann,  and  and  torn.  iii.  p.  xliv. ;  also  Pilla,  cited 
others,  referred  to  by  Boue,  Bull,  de  la  by  Murchison,  Quart.  Geol.  Journ.  vol.  v. 
Soc.  Geol.  de  France,  torn.  v.  p.  317.;  p.  266. 


620  AGE   OF   METAMORPHIC   ROCKS         [Cn.  XXXVII. 

earlier  geologists  they  would  have  ranked  as  primary  rocks.  In  that 
case  the  date  of  their  origin  would  have  been  thrown  back  to  an  era 
antecedent  to  the  deposition  of  the  Lower  Silurian  or  Cambrian 
strata,  although  in  reality  they  were  formed  in  the  Oolitic  period, 
and  altered  at  some  subsequent  and  perhaps  much  later  epoch. 

Alps  of  Switzerland. — In  the  Alps,  analogous  conclusions  have 
been  drawn  respecting  the  alteration  of  strata  on  a  still  more  ex- 
tended scale.  In  the  eastern  part  of  that  chain,  some  of  the  primary 
fossiliferous  strata,  as  well  as  the  older  secondary  formations,  toge- 
ther with  the  oolitic  and  cretaceous  rocks,  are  distinctly  recognizable. 
Tertiary  deposits  also  appear  in  a  less  elevated  position  on  the  flanks 
of  the  Eastern  Alps  ;  but  in  the  Central  or  Swiss  Alps,  the  primary 
fossiliferous  and  older  secondary  formations  disappear,  and  the  Cre- 
taceous, Oolitic,  Liassic,  and  at  some  points  even  the  Eocene  strata, 
graduate  insensibly  into  metamorphic  rocks,  consisting  of  granular 
limestone,  talc-schist,  talcose-gneiss,  micaceous  schist,  and  other 
varieties.  In  regard  to  the  age  of  this  vast  assemblage  of  crystalline 
strata,  we  can  merely  affirm  that  some  of  the  upper  portions  are 
altered  newer  secondary,  and  some  of  them  even  Eocene  deposits  ;  but 
we  cannot  avoid  suspecting  that  the  disappearance  both  of  the  older 
secondary  and  primary  fossiliferous  rocks  may  be  owing  to  their 
having  been  all  converted  in  the  same  region  into  crystalline  schist. 

It  is  difficult  to  convey  to  those  who  have  never  visited  the  Alps 
a  just  idea  of  the  various  proofs  which  concur  to  produce  this  con- 
viction. In  the  first  place,  there  are  certain  regions  where  Oolitic, 
Cretaceous,  and  Eocene  strata  have  been  turned  into  granular  marble, 
gneiss,  and  other  metamorphic  schists,  near  their  contact  with  gra- 
nite. This  fact  shows  undeniably  that  plutonic  causes  continued  to 
be  in  operation  in  the  Alps  down  to  a  late  period,  even  after  the 
deposition  of  some  of  the  nummulitic  or  middle  Eocene  formations. 
Having  established  this  point,  we  are  the  more  willing  to  believe 
that  many  inferior  fossiliferous  rocks,  probably  exposed  for  longer 
periods  to  a  similar  action,  may  have  become  metamorphic  to  a  still 
greater  extent. 

We  also  discover  in  parts  of  the  Swiss  Alps  dense  masses  of 
secondary  and  even  tertiary  strata  which  have  assumed  that  semi- 
crystalline  texture  which  Werner  called  transition,  and  which  natu- 
rally led  his  followers,  who  attached  great  importance  to  mineral 
characters  taken  alone,  to  class  them  as  transition  formations,  or  as 
groups  older  than  the  lowest  secondary  rocks.  (See  p.  93.).  Now, 
it  is  probable  that  these  strata  have  been  affected,  although  in  a  less 
intense  degree,  by  that  same  plutonic  action  which  has  entirely 
altered  and  rendered  metamorphic  so  many  of  the  subjacent  form- 
ations ;  for  in  the  Alps,  this  action  has  by  no  means  been  confined 
to  the  immediate  vicinity  of  granite.  Granite,  indeed,  and  other 
plutonic  rocks,  rarely  make  their  appearance  at  the  surface,  notwith- 
standing the  deep  ravines  which  lay  open  to  view  the  internal  struc- 
ture of  these  mountains.  That  they  exist  below  at  no  great  depth 
we  cannot  doubt,  and  we  have  already  seen  (p.  574.)  that  at  some 


€H.  XXXVII.]  OF  THE   SWISS  ALPS.  621 

points,  as  in  the  Valorsine,  near  Mont  Blanc,  granite  and  granitic 
veins  are  observable,  piercing  through  talcose  gneiss,  which  passes 
insensibly  upwards  into  secondary  strata. 

It  is  certainly  in  the  Alps  of  Switzerland  and  Savoy,  more  than  in 
any  other  district  in  Europe,  that  the  geologist  is  prepared  "to  meet 
with  the  signs  of  an  intense  development  of  plutonic  action  ;  for  here 
we  find  the  most  stupendous  monuments  of  mechanical  violence,  by 
which  strata  thousands  of  feet  thick  have  been  bent,  folded,  and 
overturned.  (See  p.  58.)  It  is  here  that  marine  secondary  form- 
ations of  a  comparatively  modern  date,  such  as  the  Oolitic  and  Cre- 
taceous, have  been  upheaved  to  the  height  of  12,000,  and  some 
Eocene  strata  to  elevations  of  10,000  feet  above  the  level  of  the 
sea  ;  and  even  deposits  of  the  Miocene  era  have  been  raised  4000  or 
5000  feet,  so  as  to  rival  in  height  the  loftiest  mountains  in  Great 
Britain. 

If  the  reader  will  consult  the  works  of  many  eminent  geologists 
who  have  explored  the  Alps,  especially  those  of  MM.  de  Beaumont, 
Studer,  Necker,  Boue,  and  Murchison,  he  will  learn  that  they  all 
share,  more  or  less  fully,  in  the  opinions  above  expressed.  It  has, 
indeed,  been  stated  by  MM.  Studer  and  Hugi,  that  there  are  com- 
plete alternations  on  a  large  scale  of  secondary  strata,  containing 
fossils,  with  gneiss  and  other  rocks  of  a  perfectly  metamorphic  struc- 
ture. I  have  visited  some  of  the  most  remarkable  localities  referred 
to  by  these  authors  ;  but  although  agreeing  with  them  that  there  are 
passages  from  the  fossiliferous  to  the  metamorphic  series  far  from  the 
contact  of  granite  or  other  plutonic  rocks,  I  was  unable  to  convince 
myself  that  the  distinct  alternations  of  highly  crystalline,  with  un- 
altered strata  above  alluded  to,  might  not  admit  of  a  different  expla- 
nation. In  one  of  the  sections  described  by  M.  Studer  in  the  highest 
of  the  Bernese  Alps,  namely  in  the  Roththal,  a  valley  bordering  the 
line  of  perpetual  snow  on  the  northern  side  of  the  Jungfrau,  there 
occurs  a  mass  of  gneiss  1000  feet  thick,  and  15,000  feet  long,  which 
I  examined,  not  only  resting  upon,  but  also  again  covered  by  strata 
containing  oolitic  fossils.  These  anomalous  appearances  may  partly 
be  explained  by  supposing  great  solid  wedges  of  intrusive  gneiss  to 
have  been  forced  in  laterally  between  strata  to  which  I  found  them 
to  be  in  many  sections  unconformable.  The  superposition,  also,  of 
the  gneiss  to  the  oolite  may,  in  some  cases,  be  due  to  a  reversal  of 
the  original  position  of  the  beds  in  a  region  where  the  convulsions 
have  been  on  so  stupendous  a  scale. 

On  the  Sattel  also,  at  the  base  of  the  Gestellihorn,  above  Enzen, 
in  the  valley  of  Urbach,  near  Meyringen,  some  of  the  intercalations 
of  gneiss  between  fossiliferous  strata  may,  I  conceive,  be  ascribed 
to  mechanical  derangement.  Almost  any  hypothesis  of  repeated 
changes  of  position  may  be  resorted  to  in  a  region  of  such  extra- 
ordinary confusion.  The  secondary  strata  may  first  have  been 
vertical,  and  then  certain  portions  may  have  become  metamorphic 
(the  plutonic  influence  ascending  from  below),  while  intervening 
strata  remained  unchanged.  The  whole  series  of  beds  may  then 


622  ORDER   OF    SUCCESSION.  [Cn.  XXXVII. 

again  have  been  thrown  into  a  nearly  horizontal  position,  giving  rise 
to  the  superposition  of  crystalline  upon  fossiliferous  formations. 

It  was  remarked,  in  Chap.  XXXIV.,  that  as  the  hypogene  rocks, 
both  stratified  and  unstratified,  crystallize  originally  at  a  certain 
depth  beneath  the  surface,  they  must  always,  before  they  are  up- 
raised and  exposed  at  the  surface,  be  of  considerable  antiquity,  rela- 
tively to  a  large  portion  of  the  fossiliferous  and  volcanic  rocks. 
They  may  be  forming  at  all  periods ;  but  before  any  of  them  can 
become  visible,  they  must  be  raised  above  the  level  of  the  sea,  and 
some  of  the  rocks  which  previously  concealed  them  must  have  been 
removed  by  denudation. 

In  Canada  the  fossiliferous  beds  of  the  Cambrian  formation  repose 
unconformably  on  gneiss,  which  was  evidently  crystalline  before  the 
deposition  of  the  Cambrian  (or  Potsdam)  sandstone.  In  Anglesea, 
as  was  before  remarked,  the  metamorphism  of  the  schists,  according 
to  the  observations  of  Professor  Ramsay,  took  place  during  the  Lower 
Silurian  period.  Coupling  these  conclusions  with  the  fact  that  a 
hypogene  texture  has  been  superinduced  in  the  Alps  on  Middle 
Eocene  deposits  (see  p.  606.),  we  cannot  doubt  that,  hereafter,  geo- 
logists will  succeed  in  detecting  crystalline  schists  of  almost  every 
age  in  the  chronological  series,  although  the  quantity  of  meta- 
morphic  rocks  visible  at  the  surface  must,  for  reasons  above  ex- 
plained, diminish  rapidly  in  proportion  as  the  monuments  of  newer 
eras  are  investigated. 

Order  of  succession  in  metamorphic  rocks.  —  There  is  no  universal 
and  invariable  order  of  superposition  in  metamorphic  rocks,  although 
a  particular  arrangement  may  prevail  throughout  countries  of  great 
extent,  for  the  same  reason  that  it  is  traceable  in  those  sedimentary 
formations  from  which  crystalline  strata  are  derived.  Thus,  for 
example,  we  have  seen  that  in  the  Apennines,  near  Carrara,  the  de- 
scending series,  where  it  is  metamorphic,  consists  of,  1st,  saccharine 
marble  ;  2ndly,  talcose-schist ;  and  3rdly,  of  quartz-rock  and  gneiss  : 
where  unaltered,  of,  1st,  fossiliferous  limestone ;  2ndly,  shale ;  and 
Srdly,  sandstone. 

But  if  we  investigate  different  mountain  chains,  we  find  gneiss, 
mica-schist,  hornblende -schist,  chlorite-schist,  hypogene  limestone, 
and  other  rocks,  succeeding  each  other,  and  alternating  with  each 
other  in  every  possible  order.  It  is,  indeed,  more  common  to  meet 
with  some  variety  of  clay-slate  forming  the  uppermost  member  of  a 
metamorphic  series  than  any  other  rock  ;  but  this  fact  by  no  means 
implies,  as  some  have  imagined,  that  all  clay-slates  were  formed  at 
the  close  of  an  imaginary  period,  when  the  deposition  of  the  crys- 
talline strata  gave  way  to  that  of  ordinary  sedimentary  deposits. 
Such  clay-slates,  in  fact,  are  variable  in  composition,  and  sometimes 
alternate  with  fossiliferous  strata,  so  that  they  may  be  said  to  belong 
almost  equally  to  the  sedimentary  and  metamorphic  order  of  rocks. 
It  is  probable  that  had  they  been  subjected  to  more  intense  plutonic 
action,  they  would  have  been  transformed  into  hornblende -schist, 
foliated  chlorite-schist,  scaly  talcose-schist,  mica-schist,  or  other 


CH.  XXXVII.]   MINERAL  CHARACTER  OF  HYPOGENE  ROCKS.   623 

more  perfectly  crystalline  rocks,  such  as  are  usually  associated  with 
gneiss. 

Uniformity  of  mineral  character  in  Hypogene  rocks.  —  Humboldt 
has  emphatically  remarked,  that  when  we  pass  to  another  hemi- 
sphere, we  see  new  forms  of  animals  and  plants,  and  even  new  con- 
stellations in  the  heavens ;  but  in  the  rocks  we  still  recognise  our 
old  acquaintances,  —  the  same  granite,  the  same  gneiss,  the  same 
micaceous  schist,  quartz-rock,  and  the  rest.  It  is  certainly  true  that 
there  is  a  great  and  striking  general  resemblance  in  the  principal 
kinds  of  hypogene  rocks,  although  of  very  different  ages  and 
countries ;  but  it  has  been  shown  that  each  of  these  are,  in  fact, 
geological  families  of  rocks,  and  not  definite  mineral  compounds. 
They  are  much  more  uniform  in  aspect  than  sedimentary  strata, 
because  these  last  are  often  composed  of  fragments  varying  greatly 
in  form,  size,  and  colour,  and  contain  fossils  of  different  shapes  and 
mineral  composition,  and  acquire  a  variety  of  tints  from  the  mixture 
of  various  kinds  of  sediment.  The  materials  of  such  strata,  if 
melted  and  made  to  crystallize,  would  be  subject  to  chemical  laws, 
simple  and  uniform  in  their  action,  the  same  in  every  climate,  and 
wholly  undisturbed  by  mechanical  and  organic  causes. 

Nevertheless,  it  would  be  a  great  error  to  assume  that  the  hypo- 
gene  rocks,  considered  as  aggregates  of  simple  minerals,  are  really 
more  homogeneous  in  their  composition  than  the  several  members  of 
the  sedimentary  series.  In  the  first  place,  different  assemblages"  of 
hypogene  rocks  occur  in  different  countries  ;  and,  secondly,  in  any 
one  district,  the  rocks  which  pass  under  the  same  name  are  often 
extremely  variable  in  their  component  ingredients,  or  at  least  in  the 
proportions  in  which  each  of  these  are  present.  Thus,  for  example, 
gneiss  and  mica-schist,  so  abundant  in  the  Grampians,  are  wanting 
in  Cumberland,  Wales,  and  Cornwall ;  in  parts  of  the  Swiss  and 
Italian  Alps,  the  gneiss  and  granite  are  talcose,  and  not  micaceous, 
as  in  Scotland ;  hornblende  prevails  in  the  granite  of  Scotland  — 
schorl  in  that  of  Cornwall  —  albite  in  the  plutonic  rocks  of  the 
Andes  —  common  felspar  in  those  of  Europe.  In  one  part  of  Scot- 
land, the  mica-schist  is  full  of  garnets;  in  another  it  is  wholly 
devoid  of  them ;  while  in  South  America,  according  to  Mr.  Darwin, 
it  is  the  gneiss,  and  not  the  mica-schist,  which  is  most  commonly 
garnetiferous.  And  not  only  do  the  proportional  quantities  of 
felspar,  quartz,  mica,  hornblende,  and  other  minerals,  vary  in  hypo- 
gene  rocks  bearing  the  same  name  ;  but  what  is  still  more  important, 
the  ingredients,  as  we  have  seen,  of  the  same  simple  mineral  are  not 
always  constant  (p.  467.,  and  table,  p.  105.). 

The  Metamorphic  strata,  why  less  calcareous  than  the  fossiliferous. 
— It  has  been  remarked,  that  the  quantity  of  calcareous  matter  in 
metamorphic  strata,  or,  indeed,  in  the  hypogene  formations  generally, 
is  far  less  than  in  fossiliferous  deposits.  Thus  the  crystalline  schists 
of  the  Grampians  in  Scotland,  consisting  of  gneiss,  mica-schist, 
•hornblende-schist,  and  other  rocks,  many  thousands  of  yards  in 
thickness,  contain  an  exceedingly  small  proportion  of  interstratified 


624  SCARCITY   OF   LIME  [Cn.  XXXVII. 

calcareous  beds,  although  these  have  been  the  objects  of  careful 
search  for  economical  purposes.  Yet  limestone  is  not  wanting  in  the 
Grampians,  and  it  is  associated  sometimes  with  gneiss,  sometimes 
with  mica-schist,  and  in  other  places  with  other  members  of  the 
metamorphic  series.  But  where  limestone  occurs  abundantly,  as  at 
Carrara,  and  in  parts  of  the  Alps,  in  connection  with  hypogene 
rocks,  it  usually  forms  one  of  the  superior  members  of  the  crys- 
talline group. 

The  scarcity,  then,  of  carbonate  of  lime  in  the  plutonic  and  meta- 
morphic rocks  generally  seems  to  be  the  result  of  some  general  cause. 
So  long  as  the  hypogene  rocks  were  believed  to  have  originated  ante- 
cedently to  the  creation  of  organic  beings,  it  was  easy  to  impute  the 
absence  of  lime  to  the  non-existence  of  those  mollusca  and  zoophytes 
by  which  shells  and  corals  are  secreted ;  but  when  we  ascribe  the 
crystalline  formations  to  plutonic  action,  it  is  natural  to  inquire 
whether  this  action  itself  may  not  tend  to  expel  carbonic  acid  and 
lime  from  the  materials  which  it  reduces  to  fusion  or  semi-fusion. 
Although  we  cannot  descend  into  the  subterranean  regions  where 
volcanic  heat  is  developed,  we  can  observe  in  regions  of  spent  vol- 
canos,  such  as  Auvergne  and  Tuscany,  hundreds  of  springs,  both  cold 
and  thermal,  flowing  out  from  granite  and  other  rocks,  and  having 
their  waters  plentifully  charged  with  carbonate  of  lime.  The  quan- 
tity of  calcareous  matter  which  these  springs  transfer,  in  the  course 
of  ages,  from  the  lower  parts  of  the  earth's  crust  to  the  superior  or 
newly  formed  parts  of  the  same,  must  be  considerable.* 

If  the  quantity  of  siliceous  and  aluminous  ingredients  brought  up 
by  such  springs  were  great,  instead  of  being  utterly  insignificant,  it 
might  be  contended  that  the  mineral  matter  thus  expelled  implies 
simply  the  decomposition  of  ordinary  subterranean  rocks ;  but  the 
prodigious  excess  of  carbonate  of  lime  over  every  other  element  must 
in  the  course  of  time,  cause  the  crust  of  the  earth  below  to  be  almost 
entirely  deprived  of  its  calcareous  constituents,  while  we  know  that 
the  same  action  imparts  to  newer  deposits,  ever  forming  in  seas  and 
lakes,  an  excess  of  carbonate  of  lime.  Calcareous  matter  is  poured 
into  these  lakes  and  the  ocean  by  a  thousand  springs  and  rivers ;  so 
that  part  of  almost  every  new  calcareous  rock  chemically  precipitated, 
and  of  many  reefs  of  shelly  and  coralline  stone,  must  be  derived  from 
mineral  matter  subtracted  by  plutonic  agency,  and  driven  up  by  gas 
and  steam  from  fused  and  heated  rocks  in  the  bowels  of  the  earth. 

Not  only  carbonate  of  lime,  but  also  free  carbonic  acid  gas  is  given 
off  plentifully  from  the  soil  and  crevices  of  rocks  in  regions  of  active 
and  spent  volcanos  as  near  Naples  and  in  Auvergne.  By  this  pro- 
cess, fossil  shells  or  corals  may  often  lose  their  carbonic  acid,  and  the 
residual  lime  may  enter  into  the  composition  of  augite,  hornblende, 
garnet,  and  other  hypogene  minerals.  That  the  removal  of  the  cal- 
careous matter  of  fossil  shells  is  of  frequent  occurrence,  is  proved  by 
the  fact  of  such  organic  remains  being  often  replaced  by  silex  or 

*  See  Principles  of  Geology  by  the  Author,  Index,  "  Calcareous  Springs," 


CH'.  XXXVII.]  IN   METAMORPHIC   ROCKS.  625 

other  minerals,  and  sometimes  by  the  space  once  occupied  by  the 
fossil  being  left  empty,  or  only  marked  by  a  faint  impression.  We 
ought  not  indeed  to  marvel  at  the  general  absence  of  organic  re- 
mains from  the  crystalline  strata,  when  we  bear  in  mind  how  often 
fossils  are  obliterated,  wholly  or  in  part,  even  in  tertiary  formations 
— how  often  vast  masses  of  sandstone  and  shale,  of  different  ages, 
and  thousands  of  feet  thick,  are  devoid  of  fossils — how  certain  strata 
may  first  have  been  deprived  of  a  portion  of  their  fossils  when  they 
became  semi-crystalline,  or  assumed  the  transition  state  of  Werner 
—  and  how  the  remaining  portion  may  have  been  effaced  when  they 
were  rendered  metamorphic.  Rocks  of  the  last-mentioned  class,  more- 
over, have  sometimes  been  exposed  again  and  again  to  renewed  plu- 
tonic  action. 


ss 


626  MINERAL    VEINS.  [Cn.  XXXVIII. 


CHAPTER  XXXVIH. 

MINERAL   VEINS. 

Werner's  doctrine  that  mineral  veins  were  fissures  filled  from  above  — Veins  of 
segregation — Ordinary  metalliferous  veins  or  lodes — Their  frequent  coincidence 
with  faults— Proofs  that  they  originated  in  fissures  in  solid  rock — Veins  shifting 
other  veins — Polishing  of  their  walls  or  "  slicken-sides." — Shells  and  pebbles  in 
lodes — Evidence  of  the  successive  enlargement  and  reopening  of  veins  — 
Fournet's  observations  in  Auvergne  —  Dimensions  of  veins  —  Why  some  alter- 
nately swell  out  and  contract — Filling  of  lodes  by  sublimation  from  below — 
Chemical  and  electrical  action — Kelative  age  of  the  precious  metals — Copper 
and  lead  veins  in  Ireland  older  than  Cornish  tin — Lead  vein  in  lias,  Glamorgan- 
shire—  Gold  in  Kussia,  California,  and  Australia. —  Connection  of  hot  springs 
and  mineral  veins — Concluding  remarks. 

THE  manner  in  which  metallic  substances  are  distributed  through  the 
earth's  crust,  and  more  especially  the  phenomena  of  those  nearly 
vertical  and  tabular  masses  of  ore  called  mineral  veins,  from  which 
the  larger  part  of  the  precious  metals  used  by  man  are  obtained, — 
these  are  subjects  of  the  highest  practical  importance  to  the  miner, 
and  of  no  less  theoretical  interest  to  the  geologist. 

The  views  entertained  respecting  metalliferous  veins  have  been 
modified,  or,  rather,  have  undergone  an  almost  complete  revolution, 
since  the  middle  of  the  last  century,  when  Werner,  as  director  of  the 
School  of  Mines,  at  Freiburg  in  Saxony,  first  attempted  to  generalize 
the  facts  then  known.  He  taught  that  mineral  veins  had  originally 
been  open  fissures  which  were  gradually  filled  up  with  crystalline 
and  metallic  matter,  and  that  many  of  them,  after  being  once  filled, 
had  been  again  enlarged  or  reopened.  He  also  pointed  out  that  veins 
thus  formed  are  not  all  referable  to  one  era,  but  are  of  various  geo- 
logical dates. 

Such  opinions,  although  slightly  hinted  at  by  earlier  writers,  had 
never  before  been  generally  received,  and  their  announcement  by  one 
of  high  authority  and  great  experience  constituted  an  era  in  the 
science.  Nevertheless,  I  have  shown,  when  tracing,  in  another  work, 
the  history  and  progress  of  geology,  that  Werner  was  far  behind  some 
of  his  predecessors  in  his  theory  of  the  volcanic  rocks,  and  less  en- 
lightened than  his  contemporary,  Dr.  Hutton,  in  his  speculations  as  to 
the  prigin  of  granite.*  According  to  him,  the  plutonic  formations,  as 
well  as  the  crystalline  schists,  were  substances  precipitated  from  a 
chaotic  fluid  in  some  primeval  or  nascent  condition  of  the  planet ; 

*  Principles  of  Geology,  chap.  iv. 


Ck.  XXXVIII.]      DIFFERENT    KINDS    OF    MINERAL   VEINS.       627 

and  the  metals,  therefore,  being  closely  connected  with  them,  had 
partaken,  according  to  him,  of  a  like  mysterious  origin.  He  also 
held  that  the  trap  rocks  were  aqueous  deposits,  and  that  dikes  of  por- 
phyry, greenstone,  and  basalt,  were  fissures  filled  with  their  several 
contents  from  above.  Hence  he  naturally  inferred  that  mineral  veins 
had  derived  their  component  materials  from  an  incumbent  ocean, 
rather  than  from  a  subterranean  source ;  that  these  materials  had 
been  first  dissolved  in  the  waters  above,  instead  of  having  risen  up 
by  sublimation  from  lakes  and  seas  of  igneous  matter  below. 

In  proportion  as  the  hypothesis  of  a  primeval  fluid,  or  "  chaotic 
menstruum,"  was  abandoned,  in  reference  to  the  plutonic  formations, 
and  when  all  geologists  had  come  to  be  of  one  mind  as  to  the  true 
relation  of  the  volcanic  and  trappean  rocks,  reasonable  hopes  began 
to  be  entertained  that  the  phenomena  of  mineral  veins  might  be 
explained  by  known  causes,  or  by  chemical,  thermal,  and  electrical 
agency  still  at  work  in  the  interior  of  the  earth.  The  grounds  of 
this  conclusion  will  be  better  understood  when  the  geological  facts 
brought  to  light  by  mining  operations  have  been  described  and 
explained. 

On  different  kinds  of  mineral  veins. — Every  geologist  is  fami- 
liarly acquainted  with  those  veins  of  quartz  which  abound  in  hypogene 
strata,  forming  lenticular  masses  of  limited  extent.  They  are  some- 
times observed,  also,  in  sandstones  and  shales.  Veins  of  carbonate 
of  lime  are  equally  common  in  fossiliferous  rocks,  especially  in  lime- 
stones. Such  veins  appear  to  have  once  been  chinks  or  small  cavities, 
caused,  like  cracks  in  clay,  by  the  shrinking  of  the  mass,  which  has 
consolidated  from  a  fluid  state,  or  has  simply  contracted  its  dimensions 
in  passing  from  a  higher  to  a  lower  temperature.  Siliceous,  calca- 
reous, and  occasionally  metallic  matters  have  sometimes  found  their 
way  simultaneously  into  such  empty  spaces,  by  infiltration  from  the 
surrounding  rocks,  or  by  segregation,  as  it  is  often  termed.  Mixed 
with  hot  water  and  steam,  metallic  ores  may  have  permeated  a  pasty 
matrix  until  they  reached  those  receptacles  formed  by  shrinkage,  and 
thus  gave  rise  to  that  irregular  assemblage  of  veins,  called  by  the 
Germans  a  "  stockwerk,"  in  allusion  to  the  different  floors  on  which 
the  mining  operations  are  in  such  cases  carried  on. 

The  more  ordinary  or  regular  veins  are  usually  worked  in  vertical 
shafts,  and  have  evidently  been  fissures  produced  by  mechanical 
violence.  They  traverse  all  kinds  of  rocks,  both  hypogene  and 
fossiliferous,  and  extend  downwards  to  indefinite  or  unknown  depths. 
We  may  assume  that  they  correspond  with  such  rents  as  we  see 
caused  from  time  to  time  by  the  shock  of  an  earthquake.  Metal- 
liferous veins,  referable  to  such  agency,  are  occasionally  a  few  inches 
wide,  but  more  commonly  3  or  4  feet.  They  hold  their  course  con- 
tinuously in  a  certain  prevailing  direction  for  miles  or  leagues, 
passing  through  rocks  varying  in  mineral  composition. 

That  metalliferous  veins  were  fissures. — As  some  intelligent  miners, 
after  an  attentive  study  of  metalliferous  veins,  have  been  unable  to 

SB  2 


628 


OKIGIN    OF 


[CH.  XXXVIII. 


Fig.  710. 


reconcile  many  of  their  characteristics  with  the  hypothesis  of  fissures, 

I  shall  begin  by  stating 
the  evidence  in  its  fa- 
vour. The  most  striking 
fact  perhaps  which  can 
be  adduced  in  its  sup- 
port is,  the  coincidence 
of  a  considerable  pro- 
portion of  mineral  veins 
withfaults,  or  those  dis- 
locations of  rocks  which 
are  indisputably  due  to 
mechanical  force,  as 
above  explained  (p.  6L). 
There  are  even  proofs 
in  almost  every  mining 
district  of  a  succession 
of  faults,  by  which  the 
opposite  walls  of  rents, 
now  the  receptacles  of 
metallic  substances,have 
suffered  displacement. 
c  Thus,  for  example,  sup- 
pose a  a,  fig.  710.,  to  be 
a  tin  lode  in  Cornwall, 
the  term  lode  being  ap- 
plied to  veins  contain- 
ing metallic  ores.  This 
lode,  running  east  and 
west,  is  a  yard  wide, 
and  is  shifted  by  a 
copper  lode  (b  b\  of 
similar  width. 

The  first  fissure  (a  a) 
has  been  filled  with 
various  materials,  partly 

Vertical  sections  of  the  mine  of  Huel  Peeve"  Redruth,  Cornwall.  °f  chemical  Origin,  Such 

as     quartz,     fluor-spar, 

peroxide  of  tin,  sulphuret  of  copper,  arsenical  pyrites,  bismuth,  and 
sulphuret  of  nickel,  and  partly  of  mechanical  origin,  comprising  clay 
and  angular  fragments  or  detritus  of  the  intersected  rocks.  The 
plates  of  quartz  and  the  ores  are,  in  some  places,  parallel  to  the  ver- 
tical sides  or  walls  of  the  vein,  being  divided  from  each  other  by 
alternating  layers  of  clay,  or  other  earthy  matter.  Occasionally  the 
metallic  ores  are  disseminated  in  detached  masses  among  the  vein- 
stones. 

It  is  clear  that,  after  the  gradual  introduction  of  the  tin  and  other 
substances,  the  second  rent  (b  b)  was  produced  by  another  fracture 
accompanied  by  a  displacement  of  the  rocks  along  the  plane  of  b  b. 


Fig.  712. 


CH.  XXXVIII.]  METALLIFEKOUS   VEINS.  629 

This  new  opening  was  then  filled  with  minerals,  some  of  them  re- 
sembling those  in  a  a,  as  fluor-spar  (or  fluate  of  lime)  and  quartz  ; 
others  different,  the  copper  being  plentiful  and  the  tin  wanting  or 
very  scarce. 

We  must  next  suppose  the  shock  of  a  third  earthquake  to  occur, 
breaking  asunder  all  the  rocks  along  the  line  c  c,  fig.  711.;  the 
fissure,  in  this  instance,  being  only  6  inches  wide,  and  simply  filled 
with  clay,  derived,  probably,  from  the  friction  of  the  walls  of  the 
rent,  or  partly,  perhaps,  washed  in  from  above.  This  new  move- 
ment has  heaved  the  rock  in  such  a  manner  as  to  interrupt  the  con- 
tinuity of  the  copper  vein  (b  6),  and,  at  the  same  time,  to  shift  or 
heave  laterally  in  the  same  direction  a  portion  of  the  tin  vein  which 
had  not  previously  been  broken. 

Again,  in  fig.  712.  we  see  evidence  of  a  fourth  fissure  (d  d),  also 
filled  with  clay,  which  has  cut  through  the  tin  vein  (a  a),  and  has 
lifted  it  slightly  upwards  towards  the  south.  The  various  changes 
here  represented  are  not  ideal,  but  are  exhibited  in  a  section  obtained 
in  working  an  old  Cornish  mine,  long  since  abandoned,  in  the  parish 
of  Redruth,  called  Huel  Peever,  and  described  both  by  Mr.  Williams 
and  Mr.  Carne.*  The  principal  movement  here  referred  to,  or  that 
of  c  c,  fig.  712.,  extends  through  a  space  of  no  less  than  84  feet;  but 
in  this,  as  in  the  case  of  the  other  three,  it  will  be  seen  that  the 
outline  of  the  country  above,  d,  c,  b,  a,  &c.,  or  the  geographical 
features  of  Cornwall,  are  not  affected  by  any  of  the  dislocations,  a 
powerful  denuding  force  having  clearly  been  exerted  subsequently 
to  all  the  faults.  (See  above,  p.  69.)  It  is  commonly  said  in  Corn- 
wall, that  there  are  eight  distinct  systems  of  veins  which  can  in  like 
manner  be  referred  to  as  many  successive  movements  or  fractures  ; 
and  the  German  miners  of  the  Hartz  Mountains  speak  also  of  eight 
systems  of  veins,  referable  to  as  many  periods. 

Besides  the  proofs  of  mechanical  action  already  explained,  the 
opposite  walls  of  veins  are  often  beautifully  polished,  as  if  glazed, 
and  are  not  unfrequently  striated  or  scored  with  parallel  furrows  and 
ridges,  such  as  would  be  produced  by  the  continued  rubbing  together 
of  surfaces  of  unequal  hardness.  These  smoothed  surfaces  resemble 
the  rocky  floor  over  which  a  glacier  has  passed  (see  fig.  p.  128). 
They  are  common  even  in  cases  where  there  has  been  no  shift,  and 
occur  equally  in  non -metalliferous  fissures.  They  are  called  by 
miners  "  slicken-sides,"  from  the  German  schlichten,  to  plane,  and  seite, 
side.  It  is  supposed  that  the  lines  of  the  striae  indicate  the  direction 
in  which  the  rocks  were  moved.  During  one  of  the  minor  earth- 
quakes in  Chili,  which  happened  about  the  year  1840,  and  was  de- 
scribed to  me  by  an  eye-witness,  the  brick  walls  of  a  building  were 
rent  vertically  in  several  places,  and  made  to  vibrate  for  several 
minutes  during  each  shock,  after  which  they  remained  uninjured, 
and  without  any  opening,  although  the  line  of  each  crack  was  still 
visible.  When  all  movement  had  ceased,  there  were  seen  on  the 

*  Geol.  Trans,  vol.  iv.  p.  139.;  Trans.  Roy.  Geol.  Society,  Cornwall,  vol.  ii.  p.  90. 

S3  3 


630  SUCCESSIVE   ENLARGEMENTS         [Cn.  XXXVIII. 

floor  of  the  house,  at  the  bottom  of  each  rent,  small  heaps  of  fine 
brickdust,  evidently  produced  by  trituration. 

In  some  of  the  veins  in  the  mountain  limestone  of  Derbyshire,  con- 
taining lead,  the  vein-stuff,  which  is  nearly  compact,  is  occasionally 
traversed  by  what  may  be  called  a  vertical  crack  passing  down  the 
middle  of  the  vein.  The  two  faces  in  contact  are  slicken -sides,  well 
polished  and  fluted,  and  sometimes  covered  by  a  thin  coating  of  lead- 
ore.  When  one  side  of  the  vein-stuff  is  removed,  the  other  side  cracks, 
especially  if  small  holes  be  made  in  it,  and  fragments  fly  off  with 
loud  explosions,  and  continue  to  do  so  for  some  days.  The  miner, 
availing  himself  of  this  circumstance,  makes  with  his  pick  small 
holes  about  6  inches  apart,  and  4  inches  deep,  and  on  his  return  in  a 
few  hours  finds  every  part  ready  broken  to  his  hand.*  These  pheno- 
mena and  their  causes  (probably  connected  with  electrical  action) 
seem  scarcely  to  have  attracted  the  notice  which  they  deserve. 

That  a  great  many  veins  communicated  originally  with  the  surface 
of  the  country  above,  or  with  the  bed  of  the  sea,  is  proved  by  the 
occurrence  in  them  of  well-rounded  pebbles,  agreeing  with  those  in 
superficial  alluviums,  as  in  Auvergne  and  Saxony.  In  Bohemia, 
such  pebbles  have  been  met  with  at  the  depth  of  180  fathoms.  In 
Cornwall,  Mr.  Carne  mentions  true  pebbles  of  quartz  and  slate  in  a 
tin  lode  of  the  Relistran  Mine,  at  the  depth  of  600  feet  below  the 
surface.  They  were  cemented  by  oxide  of  tin  land  bisulphuret  of 
copper,  and  were  traced  over  a  space  more  than  12  feet  long  and  as 
many  wide.f  Marine  fossil  shells,  also,  have  been  found  at  great 
depths,  having  probably  been  engulphed  during  submarine  earth- 
quakes. Thus,  a  gryphaea  is  stated  by  M.  Yirlet  to  have  been  met 
with  in  a  lead-mine  near  Semur,  in  France,  and  a  madrepore  in  a 
compact  vein  of  cinnabar  in  Hungary.  J 

When  different  sets  or  systems  of  veins  occur  in  the  same  country, 
those  which  are  supposed  to  be  of  contemporaneous  origin,  and  which 
are  filled  with  the  same  kind  of  metals,  often  maintain  a  general 
parallelism  of  direction.  Thus,  for  example,  both  the  tin  and  copper 
veins  in  Cornwall  run  nearly  east  and  west,  while  the  lead-veins  run 
north  and  south ;  but  there  is  no  general  law  of  direction  common  to 
different  mining  districts.  The  parallelism  of  the  veins  is  another 
reason  for  regarding  them  as  ordinary  fissures,  for  we  observe  that 
contemporaneous  trap  dikes,  admitted  by  all  to  be  masses  of  melted 
matter  which  have  filled  rents,  are  often  parallel.  Assuming,  then, 
that  veins  are  simply  fissures  in  which  chemical  and  mechanical 
deposits  have  accumulated,  we  may  next  consider  the  proofs  of  their 
having  been  filled  gradually  and  often  during  successive  enlarge- 
ments. I  have  already  spoken  of  parallel  layers  of  clay,  quartz,  and 
ore.  Werner  himself  observed,  in  a  vein  near  Gersdorff,  in  Saxony, 
no  less  than  thirteen  beds  of  different  minerals,  arranged  with  the 
utmost  regularity  on  each  side  of  the  central  layer.  This  layer  was 

*  Conyb.  and  Phil.  Geol.  p.  401.;  and  J  Fournet,  Etudes  sur  les  Depots 
Farey's  Derbysh.  p.  243.  Metalliferes. 

f  Carne,  Trans,  of  Geol.  Soc.  Corn- 
wall, vol.  iii.  p.  238. 


CH.  XXXVIII.]          AND   FILLING   UP   OF    VEINS. 


631 


formed  of  two  beds  of  calcareous  spar,  which  had  evidently  lined 
the  opposite  walls  of  a  vertical  cavity.  The  thirteen  beds  followed 
each  other  in  corresponding  order,  consisting  of  fluor-spar,  heavy 
spar,  galena,  &c.  In  these  cases,  the  central  mass  has  been  last 
formed,  and  the  two  plates  which  coat  the  outer  walls  of  the  rent 
on  each  side  are  the  oldest  of  all.  If  they  consist  of  crystalline  pre- 
cipitates, they  may  be  explained  by  supposing  the  fissure  to  have 
remained  unaltered  in  its  dimensions,  while  a  series  of  changes 
occurred  in  the  nature  of  the  solutions  which  rose  up  from  below  ; 
but  such  a  mode  of  deposition,  in  the  case  of  many  successive  and 
parallel  layers,  appears  to  be  exceptional 

If  a  veinstone  consist  of  crystalline  matter,  the  points  of  the 
crystals  are  always  turned  inwards,  or  towards  the  centre  of  the 
vein ;  in  other  words,  they  point  in  that  direction  where  there  was 
most  space  for  the  development  of  the  crystals.  Thus  each  new 
layer  receives  the  impression  of  the  crystals  of  the  preceding  layer, 
and  imprints  its  crystals  on  the  one  which  follows,  until  at  length 
the  whole  of  the  vein  is  filled  :  the  two  layers  which  meet  dovetail 
the  points  of  their  crystals  the  one  into  the  other.  But  in  Cornwall, 
some  lodes  occur  where  the  vertical  plates,  or  combs,  as  they  are 
there  called,  exhibit  crystals  so  dovetailed  as  to  prove  that  the  same 
fissure  has  been  often  enlarged.  Sir  H.  De  la  Beche  gives  the  fol- 
lowing curious  and  instructive  example  (fig.  713.)  from  a  copper-mine 


/ 

Granite , 

/ 
"/    \ 

/        _  ^ 

d  e  / 

Copper  lode,  near  Redruth,  enlarged  at  six  successive  periods. 

in  granite,  near  Redruth.*  Each  of  the  plates  or  combs  («,  5,  c,  d, 
etf)  are  double,  having  the  points  of  their  crystals  turned  inwards 
along  the  axis  of  the  comb.  The  sides  or  walls  (2,  3,  4,  5,  and  6) 
are  parted  by  a  thin  covering  of  ochreous  clay,  so  that  each  comb 
is  readily  separable  from  another  by  a  moderate  blow  of  the  hammer. 
The  breadth  of  each  represents  the  whole  width  of  the  fissure  at  six 
successive  periods,  and  the  outer  walls  of  the  vein,  where  the  first 
narrow  rent  was  formed,  consisted  of  the  granitic  surfaces  1  and  7. 

A  somewhat  analogous  interpretation  is  applicable  to  numbers 
of  other  cases,  where  clay,  sand,  or  angular  detritus  alternate  with 
ores  and  veinstones.  Thus,  we  may  imagine  the  sides  of  a  fissure  to 
be  encrusted  with  siliceous  matter,  as  Von  Buch  observed,  in  Lan- 
cerote,  the  walls  of  a  volcanic  crater  formed  in  1731  to  be  traversed 
by  an  open  rent  in  which  hot  vapours  had  deposited  hydrate  of 

*  Geol.  Rep.  on  Cornwall,  p.  340. 

s  s  4 


632  SWELLING   OUT   AND  [Cn.  XXXVIII. 

silica,  the  incrustation  nearly  extending  to  the  middle.*  Such  a 
vein  may  then  be  filled  with  clay  or  sand,  and  afterwards  re-opened, 
the  new  rent  dividing  the  argillaceous  deposit,  and  allowing  a 
quantity  of  rubbish  to  fall  down.  Various  metals  and  spars  may 
then  be  precipitated  from  aqueous  solutions  among  the  interstices  of 
this  heterogeneous  mass. 

That  such  changes  have  repeatedly  occurred,  is  demonstrated  by 
occasional  cross-veins,  implying  the  oblique  fracture  of  previously 
formed  chemical  and  mechanical  deposits.  Thus,  for  example, 
M.  Fournet,  in  his  description  of  some  mines  in  Auvergne  worked 
under  his  superintendence,  observes  that  the  granite  of  that  country 
was  first  penetrated  by  veins  of  granite,  and  then  dislocated,  so  that 
open  rents  crossed  both  the  granite  and  the  granitic  veins.  Into 
such  openings,  quartz,  accompanied  by  sulphurets  of  iron  and  ar- 
senical pyrites,  was  introduced.  Another  convulsion  then  burst 
open  the  rocks  along  the  old  line  of  fracture,  and  the  first  set  of 
deposits  were  cracked  and  often  shattered,  so  that  the  new  rent  was 
filled,  not  only  with  angular  fragments  of  the  adjoining  rocks,  but 
with  pieces  of  the  older  veinstones.  Polished  and  striated  surfaces 
on  the  sides  or  in  the  contents  of  the  vein  also  attest  the  reality  of 
these  movements.  A  new  period  of  repose  then  ensued,  during 
which  various  sulphurets  were  introduced,  together  with  hornstone 
quartz,  by  which  angular  fragments  of  the  older  quartz  before 
mentioned  were  cemented  into  a  breccia.  This  period  was  followed 
by  other  dilatations  of  the  same  veins,  and  other  sets  of  mineral 
deposits,  until,  at  last,  pebbles  of  the  basaltic  lavas  of  Auvergne, 
derived  from  superficial  alluviums,  probably  of  Miocene  or  older 
Pliocene  date,  were  swept  into  the  veins.  I  have  not  space  to 
enumerate  all  the  changes  minutely  detailed  by  M.  Fournet,  but 
they  are  valuable,  both  to  the  miner  and  geologist,  as  showing  how 
the  supposed  signs  of  violent  catastrophes  may  be  the  monuments, 
not  of  one  paroxysmal  shock,  but  of  reiterated  movements. 

Such  repeated  enlargement  and  re-opening  of  veins  might  have 
been  anticipated,  if  we  adopt  the  theory  of  fissures,  and  reflect  how 
few  of  them  have  ever  been  sealed  up  entirely,  and  that  a  country 
with  fissures  only  partially  filled  must  naturally  offer  much  feebler 
resistance  along  the  old  lines  of  fracture  than  anywhere  else.  It  is 
quite  otherwise  in  the  case  of  dikes,  where  each  opening  has  been 
the  receptacle  of  one  continuous  and  homogeneous  mass  of  melted 
matter,  the  consolidation  of  which  has  taken  place  under  consi- 
derable pressure.  Trappean  dikes  can  rarely  fail  to  strengthen  the 
rocks  at  the  points  where  before  they  were  weakest ;  and  if  the  up- 
heaving force  is  again  exerted  in  the  same  direction,  the  crust  of  the 
earth  will  give  way  anywhere  rather  than  at  the  precise  points 
where  the  first  rents  were  produced. 

A  large  proportion  of  metalliferous  veins  have  their  opposite  walls 
nearly  parallel,  and  sometimes  over  a  wide  extent  of  country.  There 

*  Principles,  ch.  xxvii.  8th  ed.  p.  422. 


CH.  XXXVIII.]  CONTRACTION   OF    VEINS.  633 

is  a  fine  example  of  this  in  the  celebrated  vein  of  Andreasburg  in 
the  Hartz,  which  has  been  worked  for  a  depth  of  500  yards  perpen- 
dicularly, and  200  horizontally,  retaining  almost  every  where  a 
width  of  3  feet.  But  many  lodes  in  Cornwall  and  elsewhere  are 
extremely  variable  in  size,  being  1  or  2  inches  in  one  part,  and  then 
8  or  10  feet  in  another,  at  the  distance  of  a  few  fathoms,  and  then 
again  narrowing  as  before.  Such  alternate  swelling  and  contraction 
is  so  often  characteristic  as  to  require  explanation.  The  walls  of 
fissures  in  general,  observes  Sir  H.  De  la  Beche,  are  rarely  perfect 
planes  throughout  their  entire  course,  nor  could  we  well  expect 
them  to  be  so,  since  they  commonly  pass  through  rocks  of  unequal 
hardness  and  different  mineral  composition.  If,  therefore,  the  op- 
posite sides  of  such  irregular  fissures  slide  upon  each  other,  that  is 
to  say,  if  there  be  a  fault,  as  in  the  case  of  so  many  mineral  veins, 
the  parallelism  of  the  opposite  walls  is  at  once  entirely  destroyed,  as 
will  be  readily  seen  by  studying  the  annexed  diagrams. 

Fig.  714. 


Let  a  b)  fig.  714.,  be  a  line  of  fracture  traversing  a  rock,  and  let 
a  b,  fig.  715.,  represent  the  same  line.  Now,  if  we  cut  a  piece  of 
paper  representing  this  line,  and  then  move  the  lower  portion  of 
this  cut  paper  sideways  from  a  to  a',  taking  care  that  the  two  pieces 
of  paper  still  touch  each  other  at  the  points  1,  2,  3,  4,  5,  we  obtain 
an  irregular  aperture  at  c,  and  isolated  cavities  &tddd,  and  when 
we  compare  such  figures  with  nature  we  find  that,  with  certain 
modifications,  they  represent  the  interior  of  faults  and  mineral  veins. 
If,  instead  of  sliding  the  cut  paper  to  the  right  hand,  we  move  the 
lower  part  towards  the  left,  about  the  same  distance  that  it  was 
previously  slid  to  the  right,  we  obtain  considerable  variation  in  the 
cavities  so  produced,  two  long  irregular  open  spaces,  fft  fig.  716., 
being  then  formed.  This  will  serve  to  show  to  what  slight  cir- 
cumstances considerable  variations  in  the  character  of  the  openings 
between  unevenly  fractured  surfaces  may  be  due,  such  surfaces 
being  moved  upon  each  other,  so  as  to  have  numerous  points  of 
contact. 

Most  lodes  are  perpendicular  to  the  horizon,  or  nearly  so;  but 
some  of  them  have  a  considerable  inclination  or  "  hade,"  as  it  is 
termed,  the  angles  of  dip  varying  from  15°  to  45°.  The  course 
of  a  vein  is  frequently  very  straight ;  but  if  tortuous,  it  is  found 
to  be  choked  up  with  clay,  stones,  and  pebbles,  at  points  where  it 
departs  most  widely  from  verticality.  Hence  at  places,  such  as  a, 


634  CHEMICAL   DEPOSITS    IN   VEINS.       [Cn.  XXXVIII. 

Fig.  717.  %•  717.,  the  miner  complains  that  the  ores  are 
"nipped,"  or  greatly  reduced  in  quantity,  the  space 
for  their  free  deposition  having  been  interfered  with  in 
consequence  of  the  pre-occupancy  of  the  lode  by  earthy 
materials.  When  lodes  are  many  fathoms  wide,  they 
are  usually  filled  for  the  most  part  with  earthy  matter, 
and  fragments  of  rock,  through  which  the  ores  are 
much  disseminated.  The  metallic  substances  frequently 
coat  or  encircle  detached  pieces  of  rock,  which  our 
miners  call  "  horses  "  or  "  riders."  That  we  should  find 
some  mineral  veins  which  split  into  branches  is  also 
natural,  for  we  observe  the  same  in  regard  to  open  fissures. 

Chemical  deposits  in  veins. — If  we  now  turn  from  the  mechanical 
to  the  chemical  agencies  which  have  been  instrumental  in  the  pro- 
duction of  mineral  veins,  it  may  be  remarked  that  those  parts  of 
fissures  which  were  not  choked  up  with  the  ruins  of  fractured  rocks 
must  always  have  been  filled  with  water ;  and  almost  every  vein  has 
probably  been  the  channel  by  which  hot  springs,  so  common  in 
countries  of  volcanos  and  earthquakes,  have  made  their  way  to  the 
surface.  For  we  know  that  the  rents  in  which  ores  abound  extend 
downwards  to  vast  depths,  where  the  temperature  of  the  interior  of 
the  earth  is  more  elevated.  We  also  know  that  mineral  veins  are 
most  metalliferous  near  the  contact  of  plutonic  and  stratified  for- 
mations, especially  where  the  former  send  veins  into  the  latter,  a 
circumstance  which  indicates  an  original  proximity  of  veins  at  their 
inferior  extremity  to  igneous  and  heated  rocks.  It  is  moreover  ac- 
knowledged that  even  those  mineral  and  thermal  springs  which,  in 
the  present  state  of  the  globe,  are  far  from  volcanos,  are  neverthe- 
less observed  to  burst  out  along  great  lines  of  upheaval  and  dislo- 
cation of  rocks.*  It  is  also  ascertained  that  all  the  substances  with 
which  hot  springs  are  impregnated  agree  with  those  discharged  in  a 
gaseous  form  from  volcanos.  Many  of  these  bodies  occur  as  vein- 
stones ;  such  as  silex,  carbonate  of  lime,  sulphur,  fluor-spar,  sulphate 
of  barytes,  magnesia,  oxide  of  iron,  and  others.  I  may  add  that,  if 
veins  have  been  filled  with  gaseous  emanations  from  masses  of 
melted  matter,  slowly  cooling  in  the  subterranean  regions,  the  con- 
traction of  such  masses  as  they  pass  from  a  plastic  to  a  solid  state 
would,  according  to  the  experiments  of  Deville  on  granite  (a  rock 
which  may  be  taken  as  a  standard),  produce  a  reduction  in  volume 
amounting  to  10  per  cent.  The  slow  crystallization,  therefore,  of 
such  plutonic  rocks  supplies  us  with  a  force  not  only  capable  of 
rending  open  the  incumbent  rocks  by  causing  a  failure  of  support, 
but  also  of  giving  rise  to  faults  whenever  one  portion  of  the  earth's 
crust  subsides  slowly  while  another  contiguous  to  it  happens  to  rest 
on  a  different  foundation,  so  as  to  remain  unmoved. 

Although  we  are  led  to  infer,  from  the  foregoing  reasoning,  that 
there  has  often  been  an  intimate  connection  between  metalliferous 

*  See  Dr.  Daubeny's  Volcanos. 


CH.  XXXVTIT.]      CHEMICAL    DEPOSITS   IN   VEINS.  635 

veins  and  hot  springs  holding  mineral  matter  in  solution,  yet  we 
must  not  on  that  account  expect  that  the  contents  of  hot  springs  and 
mineral  veins  would  be  identical.  On  the  contrary,  M.  E.  de  Beau- 
mont has  judiciously  observed  that  we  ought  to  find  in  veins  those 
substances  which,  being  least  soluble,  are  not  discharged  by  hot 
springs, — or  that  class  of  simple  and  compound  bodies  which  the 
thermal  waters  ascending  from  below  would  first  precipitate  on  the 
walls  of  a  fissure,  as  soon  as  their  temperature  began  slightly  to 
diminish.  The  higher  they  mount  towards  the  surface,  the  more 
will  they  cool,  till  they  acquire  the  average  temperature  of  springs, 
being  in  that  case  chiefly  charged  with  the  most  soluble  substances, 
such  as  the  alkalis,  soda  and  potash.  These  are  not  met  with  in 
veins,  although  they  enter  so  largely  into  the  composition  of  granitic 
rocks.* 

To  a  certain  extent,  therefore,  the  arrangement  and  distribution  of 
metallic  matter  in  veins  may  be  referred  to  ordinary  chemical  action, 
or  to  those  variations  in  temperature,  which  waters  holding  the  ores 
in  solution  must  undergo,  as  they  rise  upwards  from  great  depths  in 
the  earth.  But  there  are  other  phenomena  which  do  not  admit  of 
the  same  simple  explanation.  Thus,  for  example,  in  Derbyshire, 
veins  containing  ores  of  lead,  zinc,  and  copper,  but  chiefly  lead, 
traverse  alternate  beds  of  limestone  and  greenstone.  The  ore  is 
plentiful  where  the  walls  of  the  rent  consist  of  limestone,  but  is 
reduced  to  a  mere  string  when  they  are  formed  of  greenstone,  or 
"toad-stone,"  as  it  is  called  provincially.  Not  that  the  original 
fissure  is  narrower  where  the  greenstone  occurs,  but  because  more 
of  the  space  is  there  filled  with  veinstones,  and  the  waters  at  such 
points  have  not  parted  so  freely  with  their  metallic  contents. 

"Lodes  in  Cornwall,"  says  Mr.  Robert  W.  Fox,  "  are  very  much 
influenced  in  their  metallic  riches  by  the  nature  of  the  rock  which 
they  traverse,  and  they  often  change  in  this  respect  very  suddenly, 
in  passing  from  one  rock  to  another.  Thus  many  lodes  which  yield 
abundance  of  ore  in  granite,  are  unproductive  in  clay-slate,  or  killas, 
and  vice  versa.  The  same  observation  applies  to  killas  and  the 
granitic  porphyry  called  elvan.  Sometimes,  in  the  same  continuous 
vein,  the  granite  will  contain  copper,  and  the  killas  tin,  or  vice 
versa."  j*  Mr.  Fox,  after  ascertaining  the  existence  at  present  of 
electric  currents  in  some  of  the  metalliferous  veins  in  Cornwall,  has 
speculated  on  the  probability  of  the  same  cause  having  acted  origin- 
ally on  the  sulphurets  and  muriates  of  copper,  tin,  iron,  and  zinc, 
dissolved  in  the  hot  water  of  fissures,  so  as  to  determine  the  peculiar 
mode  of  their  distribution.  After  instituting  experiments  on  this 
subject,  he  even  endeavoured  to  account  for  the  prevalence  of  an 
east  and  west  direction  in  the  principal  Cornish  lodes  by  their  posi- 
tion at  right  angles  to  the  earth's  magnetism ;  but  Mr.  Kenwood 
and  other  experienced  miners  have  pointed  out  objections  to  the 
theory  ;  and  it  must  be  owned  that  the  direction  of  veins  in  different 

*  Bulletin,  iv.  p.  1278.  f  E.  W.  Fox  on  Mineral  Veins,  p.  10, 


636  RELATIVE   AGE    OF    METALS.         [On.  XXXVIII. 

mining  districts  varies  so  entirely  that  it  seems  to  depend  on  lines  of 
fracture,  rather  than  on  the  laws  of  voltaic  electricity.  Neverthe- 
less, as  different  kinds  of  rock  would  be  often  in  different  electrical 
conditions,  we  may  readily  believe  that  electricity  must  often  govern 
the  arrangement  of  metallic  precipitates  in  a  rent. 

"  I  have  observed,"  says  Mr.  R.  Fox,  "  that  when  the  chloride  of 
tin  in  solution  is  placed  in  the  voltaic  circuit,  part  of  the  tin  is  de- 
posited in  a  metallic  state  at  the  negative  pole,  and  part  at  the  positive 
one,  in  the  state  of  a  peroxide,  such  as  it  occurs  in  our  Cornish 
mines.  This  experiment  may  serve  to  explain  why  tin  is  found  con- 
tiguous to,  and  intermixed  with,  copper  ore,  and  likewise  separated 
from  it,  in  other  parts  of  the  same  lode."  * 

Relative  age  of  the  different  metals. —  After  duly  reflecting  on  the 
facts  above  described,  we  cannot  doubt  that  mineral  veins,  like  erup- 
tions of  granite  or  trap,  are  referable  to  many  distinct  periods  of  the 
earth's  history,  although  it  may  be  more  difficult  to  determine  the 
precise  age  of  veins ;  because  they  have  often  remained  open  for 
ages,  and  because,  as  we  have  seen,  the  same  fissure,  after  having 
been  once  filled,  has  frequently  been  re-opened  or  enlarged.  But 
besides  this  diversity  of  age,  it  has  been  supposed  by  some  geologists 
that  certain  metals  have  been  produced  exclusively  in  earlier,  others 
in  more  modern  times, — that  tin,  for  example,  is  of  higher  antiquity 
than  copper,  copper  than  lead  or  silver,  and  all  of  them  more  ancient 
than  gold.  I  shall  first  point  out  that  the  facts  once  relied  upon  in 
support  of  some  of  these  views  are  contradicted  by  later  experience, 
and  then  consider  how  far  any  chronological  order  of  arrangement 
can  be  recognised  in  the  position  of  the  precious  and  other  metals  in 
the  earth's  crust. 

In  the  first  place,  it  is  not  true  that  veins  in  which  tin  abounds 
are  the  oldest  lodes  worked  in  Great  Britain.  The  government  sur- 
vey of  Ireland  has  demonstrated,  that  in  Wexford  veins  of  copper 
and  lead  (the  latter  as  usual  being  argentiferous)  are  much  older 
than  the  tin  of  Cornwall.  In  each  of  the  two  countries  a  very 
similar  series  of  geological  changes  has  occurred  at  two  distinct 
epochs, — in  Wexford,  before  the  Devonian  strata  were  deposited  ; 
in  Cornwall,  after  the  carboniferous  epoch.  To  begin  with  the  Irish 
mining  district :  We  have  granite  in  Wexford,  traversed  by  granite 
veins,  which  veins  also  intrude  themselves  into  the  Silurian  strata, 
the  same  Silurian  rocks  as  well  as  the  veins  having  been  denuded 
before  the  Devonian  beds  were  superimposed.  Next  we  find,  in  the 
same  county,  that  elvans,  or  straight  dikes  of  porphyritic  granite, 
have  cut  through  the  granite  and  the  veins  before  mentioned,  but 
have  not  penetrated  the  Devonian  rocks.  Subsequently  to  these 
elvans,  veins  of  copper  and  lead  were  produced,  being  of  a  date  cer- 
tainly posterior  to  the  Silurian,  and  anterior  to  the  Devonian ;  for 
they  do  not  enter  the  latter,  and,  what  is  still  more  decisive,  streaks 
or  layers  of  derivative  copper  have  been  found  near  Wexford  in  the 

*  E.  W.  Fox  on  Mineral  Veins,  p.  38. 


CH.  XXXVIII.]         RELATIVE   AGE    OF    METALS.  637 

Devonian,  not  far  from  points  where  mines  of  copper  are  worked  in 
the  Silurian  strata.* 

Although  the  precise  age  of  such  copper  lodes  cannot  be  defined, 
we  may  safely  affirm  that  they  were  either  filled  at  the  close  of  the 
Silurian  or  commencement  of  the*  Devonian  period.  Besides  copper, 
lead,  and  silver,  there  is  some  gold  in  these  ancient  or  primary 
metalliferous  veins.  A  few  fragments  also  of  tin  found  in  Wicklow 
in  the  drift  are  supposed  to  have  been  derived  from  veins  of  the 
same  age.f 

Next,  if  we  turn  to  Cornwall,  we  find  there  also  the  monuments 
of  a  very  analogous  sequence  of  events.  First  the  granite  was 
formed ;  then,  about  the  same  period,  veins  of  fine-grained  granite, 
often  tortuous  (see  fig.  692.,  p.  574.),  penetrating  both  the  outer  crust 
of  granite  and  the  adjoining  fossiliferous  or  primary  rocks,  including 
the  coal-measures;  thirdly,  elvans,  holding  their  course  straight 
through  granite,  granitic  veins,  and  fossiliferous  slates;  fourthly, 
veins  of  tin  also  containing  copper,  the  first  of  those  eight  systems 
of  fissures  of  different  ages  already  alluded  to,  p.  629.  Here,  then, 
the  tin  lodes  are  newer  than  the  elvans.  It  has  indeed  been  stated 
by  some  Cornish  miners  that  the  elvans  are  in  some  few  instances 
posterior  to  the  oldest  tin -bearing  lodes,  but  the  observations  of  Sir 
H.  de  la  Beche  during  the  survey  led  him  to  an  opposite  conclusion, 
and  he  has  shown  how  the  cases  referred  to  in  corroboration  can 
be  otherwise  interpreted.^  We  may,  therefore,  assert  that  the  most 
ancient  Cornish  lodes  are  younger  than  the  coal-measures  of  that 
part  of  England,  and  it  follows  that  they  are  of  a  much  later  date 
than  the  Irish  copper  and  lead  of  Wexford  and  some  adjoining 
counties.  How  much  later,  it  is  not  so  easy  to  declare,  although 
probably  they  are  not  newer  than  the  beginning  of  the  Permian 
period,  as  no  tin  lodes  have  been  discovered  in  any  red  sandstone 
of  the  Poikilitic  group,  which  overlies  the  coal  in  the  south-west  of 
England. 

There  are  lead  veins  in  the  Mendip  hills  which  extend  through 
the  mountain  limestone  into  the  Permian  or  Dolomitic  conglomerate, 
and  others  in  Glamorganshire  which  enter  the  lias.  Those  worked 
near  Frome,  in  Somersetshire,  have  been  traced  into  the  Inferior 
Oolite.  In  Bohemia,  the  rich  veins  of  silver  of  Joachimsthal  cut 
through  basalt  containing  olivine,  which  overlies  tertiary  lignite,  in 
which  are  leaves  of  dicotyledonous  trees.  This  silver,  therefore,  is 
decidedly  a  tertiary  formation.  In  regard  to  the  age  of  the  gold  of 
the  Ural  Mountains,  in  Russia,  which,  like  that  of  California,  is  ob- 
tained chiefly  from  auriferous  alluvium,  it  occurs  in  veins  of  quartz 
in  the  schistose  and  granitic  rocks  of  that  chain,  and  is  supposed  by 
MM.  Murchison,  De  Verneuil,  and  Keyserling  to  be  newer  than  the 
syenitic  granite  of  the  Ural — perhaps  of  tertiary  date.  They  ob- 

*  I  am  indebted  to  Sir  H.  De  la  Beche  f  Sir  H.  De  la  Beche,  MS.  notes  on 
for  this  information.  See  also  maps  and  Irish  Survey. 

sections  of  Irish  Survey.  J  Report  on  Geology  of  Cornwall, 

p.  310, 


638  GOLD    OF    AUSTRALIA.  [Cn.  XXXVIII. 

serve,  that  no  gold  has  yet  been  found  in  the  Permian  conglomerates 
which  lie  at  the  base  of  the  Ural  Mountains,  although  large  quantities 
of  iron  and  copper  detritus  are  mixed  with  the  pebbles  of  those 
Permian  strata.  Hence  it  seems  that  the  Uralian  quartz  veins,  con- 
taining gold  and  platinum,  were  not  formed  or  certainly  not  exposed 
to  aqueous  denudation  during  the  Permian  era. 

In  the  auriferous  alluvium  of  Russia,  California,  and  Australia,  the 
bones  of  extinct  land-quadrupeds  have  been  met  with,  those  of  the 
mammoth  being  common  in  the  gravel  at  the  foot  of  the  Ural  Moun- 
tains, while  in  Australia  they  consist  of  huge  marsupials,  some  of  them 
of  the  size  of  the  rhinoceros  and  allied  to  the  living  wombat.  They 
belong  to  the  genera  Diprotodon  and  Nototherium  of  Professor  Owen. 
The  gold  of  Northern  Chili  is  associated  in  the  mines  of  Los  Hornos 
with  copper  pyrites,  in  veins  traversing  the  cretaceo-oolitic  forma- 
tions, so  called  because  its  fossils  have  the  character  partly  of  the 
cretaceous  and  partly  of  the  oolitic  fauna  of  Europe.*  The  gold 
found  in  the  United  States,  in  the  mountainous  parts  of  Virginia, 
North  and  South  Carolina,  and  Georgia  occurs  in  metamorphic  Silu- 
rian strata,  as  well  as  in  auriferous  gravel  derived  from  the  same. 

Gold  has  now  been  detected  in  almost  every  kind  of  rock,  in  slate, 
quartzite,  sandstone,  limestone,  granite,  and  serpentine,  both  in  veins 
and  in  the  rocks  themselves  at  short  distances  from  the  veins.  In  Aus- 
tralia it  has  been  worked  successfully  not  only  in  alluvium,  but  in 
veinstones  in  the  native  rock,  generally  consisting  of  Silurian  shales 
and  slates.  It  has  been  traced  on  that  continent,  over  more  than 
nine  degrees  of  latitude  (between  the  parallels  of  the  30°  and  39°  S.), 
and  over  twelve  of  longitude,  and  yields  already  an  annual  supply 
equal,  if  not  superior,  to  that  of  California ;  nor  is  there  any 
apparent  prospect  of  this  supply  diminishing,  still  less  of  the  ex- 
haustion of  the  gold  fields.  It  seems  reasonable,  therefore,  to  share 
the  anticipations  of  M.  Delesse  that  the  time  will  come,  and  cannot 
be  very  remote,  when  a  marked  .depreciation  will  be  experienced  in 
the  value  of  this  metal,  f 

It  has  been  remarked  by  M.  de  Beaumont,  that  lead  and  some 
other  metals  are  found  in  dikes  of  basalt  and  greenstone,  as  well  as 
in  mineral  veins  connected  with  trap  rocks,  whereas  tin  is  met  with 
in  granite  and  in  veins  associated  with  the  granitic  series.  If  this 
rule  hold  true  generally,  the  geological  position  of  tin  in  localities 
accessible  to  the  miners  will  belong,  for  the  most  part,  to  rocks  older 
than  those  bearing  lead.  The  tin  veins  will  be  of  higher  relative 
antiquity  for  the  same  reason  that  the  "  underlying  "  igneous  for- 
mations or  granites  which  are  visible  to  man  are  older,  on  the  whole, 
than  the  overlying  or  trappean  formations. 

If  different  sets  of  fissures,  originating  simultaneously  at  different 
levels  in  the  earth's  crust,  and  communicating,  some  of  them  with 
volcanic,  others  with  heated  plutonic  masses,  be  filled  with  different 

*  Darwin's  S.  America,  p.  209.,  &c.  f  Annales  des  Mines,  1853,  torn.  iii. 

p.  185. 


OH.  XXXVIII.]  CONCLUDING   KEMARKS.  639 

metals,  it  will  follow  that  those  formed  farthest  from  the  surface  will 
usually  require  the  longest  time  before  they  can  be  exposed  super- 
ficially. In  order  to  bring  them  into  view,  or  within  reach  of  the 
miner,  a  greater  amount  of  upheaval  and  denudation  must  take  place 
in  proportion  as  they  have  lain  deeper  when  first  moved.  A  con- 
siderable series  of  geological  revolutions  must  intervene  before  any 
part  of  the  fissure,  which  has  been  for  ages  in  the  proximity  of  the 
plutonic  rocks,  so  as  to  receive  the  gases  discharged  from  it  when  it 
was  cooling,  can  emerge  into  the  atmosphere.  But  I  need  not  enlarge 
on  this  subject,  as  the  reader  will  remember  what  was  said  in  the 
30th,  34th,  and  37th  chapters,  on  the  chronology  of  the  volcanic  and 
hypogene  formations. 


Concluding  Remarks.  —  The  theory  of  the  origin  of  the  hypogene 
rocks,  at  a  variety  of  successive  periods,  as  expounded  in  two  of  the 
chapters  just  cited,  and  still  more  the  doctrine  that  such  rocks  may 
be  now  in  the  daily  course  of  formation,  has  made  and  still  makes  its 
way,  but  slowly,  into  favour.  The  disinclination  to  embrace  it  has 
arisen  partly  from  an  inherent  obscurity  in  the  very  nature  of  the 
evidence  of  plutonic  action  when  developed  on  a  great  scale,  at  par- 
ticular periods.  It  has  also  sprung,  in  some  degree,  from  extrinsic 
considerations ;  many  geologists  having  been  unwilling  to  believe  the 
doctrine  of  transmutation  of  fossiliferous  into  crystalline  rocks, 
because  they  were  desirous  of  finding  proofs  of  a  beginning,  and  of 
tracing  back  the  history  of  our  terraqueous  system  to  times  anterior 
to  the  creation  of  organic  beings.  But  if  these  expectations  have  been 
disappointed,  if  we  have  found  it  impossible  to  assign  a  limit  to  that 
time  throughout  which  it  has  pleased  an  Omnipotent  and  Eternal 
Being  to  manifest  his  creative  power,  we  have  at  least  succeeded 
beyond  all  hope  in  carrying  back  our  researches  to  times  antecedent 
to  the  existence  of  man.  We  can  prove  that  man  had  a  beginning, 
and  that,  all  the  species  now  contemporary  with  man,  and  many  others 
which  preceded,  had  also  a  beginning,  and  that,  consequently,  the 
present  state  of  the  organic  world  has  not  gone  on  from  all  eternity, 
as  some  philosophers  have  maintained. 

It  can  be  shown  that  the  earth's  surface  has  been  remodelled  again 
and  again  ;  mountain  chains  have  been  raised  or  sunk ;  valleys  formed, 
filled  up,  and  then  re-excavated ;  sea  and  land  have  changed  places ; 
yet  throughout  all  these  revolutions,  and  the  consequent  alterations  of 
local  and  general  climate,  animal  and  vegetable  life  has  been  sus- 
tained. This  has  been  accomplished  without  violation  of  the  laws 
now  governing  the  organic  creation,  by  which  limits  are  assigned  to 
the  variability  of  species.  The  succession  of  living  beings  appears 
to  have  been  continued  not  by  the  transmutation  of  species,  but  by 
the  introduction  into  the  earth  from  time  to  time  of  new  plants  and 
animals,  and  each  assemblage  of  new  species  must  have  been  ad- 
mirably fitted  for  the  new  states  of  the  globe  as  they  arose,  01*  they 


640  CONCLUDING   REMARKS.  [Cn.  XXXVIII. 

would  not  have  increased  and  multiplied  and  endured  for  indefinite 
periods.* 

Astronomy  has  been  unable  to  establish  the  plurality  of  habitable 
worlds  throughout  space,  however  favourite  a  subject  of  conjecture 
and  speculation  ;  but  geology,  although  it  cannot  prove  that  other 
planets  are  peopled  with  appropriate  races  of  living  beings,  has  de- 
monstrated the  truth  of  conclusions  scarcely  less  wonderful, — the 
existence  on  our  own  planet  of  so  many  habitable  surfaces,  or  worlds 
as  they  have  been  called,  each  distinct  in  time,  and  peopled  with  its 
peculiar  races  of  aquatic  and  terrestrial  beings. 

The  proofs  now  accumulated  of  the  close  analogy  between  extinct 
and  recent  species  are  such  as  to  leave  no  doubt  on  the  mind  that 
the  same  harmony  of  parts  and  beauty  of  contrivance  which  we 
admire  in  the  living  creation  has  equally  characterized  the  organic 
world  at  remote  periods.  Thus  as  we  increase  our  knowledge  of  the 
inexhaustible  variety  displayed  in  living  nature,  and  admire  the  in- 
finite wisdom  and  power  which  it  displays,  our  admiration  is  multi- 
plied by  the  reflection,  that  it  is  only  the  last  of  a  great  series  of  pre- 
existing creations,  of  which  we  cannot  estimate  the  number  or  limit 
in  times  pastf 

*  See  Principles  of  Geol.,  Book  3.  the  Geol.  Soc.  1837.     Proceedings  G 

f  See  the  author's  Anniv.  Address  to      S.  vol.  ii.  p.  520. 


INDEX. 


[The  Fossils,  the  names  of  which  are  printed  in  Italics,  are  figures  in  the  volume.'] 


ABICH,  M.,  on  trachytic  rocks,  471. 
Acrodus  nobilis,  tooth  of,  322. 
Acrolepis  Sedgwickii,  scale  of,  357. 
Action  acutus,  great  oolite,  309. 
Actinolite-schist,  597. 
jtfchmodus,  scales  and  outline  of,  322. 
JEgean  Sea,  mud  of,  35. 

,  animal  life  in  depths  of,  137. 

JEpiornis  of  Madagascar,  350. 

Agglomerate,  volcanic  rock,  475,  476. 

Agnostus  integer,  A.  rex,  454. 

Agassiz,  M.,  cited,  87.  5sl8.  322.  351.  400.  419.  422. 

,  on  fossil  fishes  of  molasse  and  faluns,  171. 

,  on  fossil  fish  of  lias,  321. 

,  on  fossil  fish  in  Permian  marl-slate,  356. 

,  on  fish  from  Sheppey,  218. 

,  on  foot-prints,  350. 

— ,  on  fishes  of  brown-coal,  545. 

,  on  glaciers,  547.  550. 

Age,  test  of,  by  fragments  of  older  rock,  102. 

of  metamorphic  rocks,  618. 

,  test  of,  in  plutonic  rocks,  579. 

,  of  Spanish  volcanos,  541. 

— ,  of  volcanic  rocks,  how  tested,  523.  526. 

Air-breathers  in  coal,  rarity  of,  405. 

Aix-la-Chapelle,  hot  springs  at,  602. 

Alabama,  creiaceous  shingle  of,  256. 

Alabaster  defined,  13. 

Albert!  on  the  Keuper,  335. 

Alexander,  Capt.,  marine  shells  in  crag  found  by,  156 

Alluvium,  term  explained,  79. 

,  formation  of,  81. 

—  in  Auvergne,  80. 
Alpine  blocks  on  the  Jura,  149. 
erratics,  147. 

Alps,  curved  strata  of,  58. 

,  elevated  fossiliferous  rocks  in,  4. 

. ,  munmulitic  formation  of,  231. 

— ,  of  Switzerland,  620. 

,  Swiss  and  Savoy,  cleavage  of,  608. 

Altered  rocks,  483. 

by  subterranean  gases,  602. 

Alternations  of  rocks,  14. 

—  of  marine  and  freshwater  formations,  32. 
Alum-schists,  Silurian,  of  Sweden,  455. 
Alumine  in  rocks,  11. 

Amblyrhynchus  crislatus  (recent),  326. 

America,  North,  Lithodomi  in  beaches  of,  78. 

,  South,  cretaceous  strata,  256. 

,  South,  fossils  of,  164. 

,  South,  gradual  rise  of  parts  of,  46. 

Ammonites  bifrons,  A,  Nodotiantts,  ?,  A.  slriatitlus 
A.  Walcottii,31Q;  A.  Braikenridgii,  A.  margnri 
tatus,A.Stokesii,  A.  strialulus,  317  ;  A.  Elizabeths 
A.  Jason,  305  ;A.  Humpkresianus,  316  ;  A.  Rho 
tomagensis,  252. 

Ampelite,  or  aluminous  slate,  597. 


Amphibole,  469. 

Amphibolite,  or  hornblende  rock,  476.  597. 
Amphistegina  Hauerina,  eocene,  180. 
Amphitherium  Broderipii,  jaw  of,  312. 

Prevo&tii,  jaw  of,  312 

Ampullaria  glauca  (recent),  30. 
Amsterdam,  or  St.  Paul  Island,  512. 
Amygdaloid,  472. 
Ananchytes  ovatus,  chalk,  244. 
Ancillaria  subulata,  eocene,  31 . 
Ancyloceras  gigas,  259  ;  A.  spinigerum,  252. 
Ancylus  elegans,  pleistocene,  29. 
Andelys,  chalk-cliffs  at,  269. 
Andernach,  strata  near,  545. 
Andes,  plutonic  rocks  of,  583. 

,  rocks  drifted  from,  to  Chiloe,  151. 

Andesite,  471. 

Anodonta  Cordierii,  A.  latimarginatus  (recent),  28. 

Anoplotherium  commune,  tooth  of,  211. 

gracile,  outline  of,  226. 

Anthophyllum  lineatum,  183. 
Antholithes,  coal,  374. 
Anthracite  in  Rhode  Island,  604. 
Anticlinal  line,  48.  57. 
Antrim  basalt,  age  of,  181. 

,  rocks  altered  by  dikes  in,  484. 

Antwerp,  strata  like  Suffolk  crag  near,  174. 

Apateon  pedestris,  a  carboniferous  reptile,  400. 

Aphanite,  or  cornean,  476. 

Apennines,  limestone  in  482. 

Appalachian  coal-field,  393. 

Appalachians,  altered  rocks  in,  604. 

Apiocrinites  rotundus,  oolite,  307. 

Aptychus  lattts,  oolite,  303. 

Apteryx  in  New  Zealand,  165. 

Apus?  dubius,  coal, 388. 

Aqueous  rocks  defined,  2. 

rocks,  mineral  character  of,  98. 

deposits,  superposition  of,  97. 

Aralo-Caspian  formations,  176. 
Arbroa'h  paving-stone,  419. 

,  section  from,  to  the  Orampians,  48. 

Archegosaurus  medius,  skin  of,  A.  minor t  coal-mea- 
sures, 401 . 
Archiac,  M.d',  cited,  150. 

,  on  fossils  in  chalk,  252. 

,  on  shells  in  French  lower  eocene,  229. 

Ardeche,  lava  in,  488. 
Arenaceous  rocks  described,  11. 
Argillaceous  rocks,  11. 

schist,  596. 

Argile  plastique,  or  lower  eocene,  230. 

Argvleshire,  trap-vein  in  cliff,  481. 

Argyll,  Duke  of,  on  Isle  of  Mull  tertiaries,  180. 

Arkose,  597. 

Arran,  age  of  granite  in,  589. 

,  section  of,  591. 

TT 


642 


INDEX. 


Arran,  dike  of  greenstone  in,  481. 
Arrangement  of  fossils  in  strata,  5.  21. 
Arthur's  Seat,  altered  strata  of,  485. 
Arvicola,  tooth  of,  168. 
Asaphus  tyrannus,  lower  Silurian,  444. 
Aspidura  loricala,  Permian,  336. 
Astarte  bipartite,  A.  Omalii,  172. 

borealis,  131  ;  A.  Laurentiana,  141. 

Asterophyttitesfoliosa,  coal,  369. 

Astrangia  lineuta,  183. 

Astropecten  crispattis,  eocene,  219. 

Athyris  navicula,  Aymestry,  435. 

Ashby-de-la-Zouch,  fault  in  coal-field  of,  69. 

Ascension,  lamination  of  volcanic  rocks  in,  613. 

Asti,  formations  at,  175. 

Atherfield,  cretaceous  strata  of,  258. 

Atrium  of  a  volcano,  506. 

Atrypa  reticularis,  Aymestry,  438. 

Aturia  ziczac,  London  clay,  219. 

Augite,  470. 

Aulopora  serpens,  Devonian,  426. 

Auricula  (recent),  '219. 

Aurillac,  freshwater  strata  of,  205. 

Austen,  Mr.  R.  A.  G.,  on  phosphate  of  lime,  252. 

,  on  upper  green-sand,  251. 

Australia,  auriferous  gravel  of,  638. 

,  cave-breccias  of,  162. 

,  extinct  mammals  in  auriferous  gravel  of,  638. 

Auvergne,  freshwater  formations,  203. 

,  succession  of  changes  in,  197. 

,  lacustrine  strata,  200. 

,  mineral  veins  of,  632. 

—— ,  indusial  limestone,  of  202. 

,  extinct  volcanos  of,  550. 

,  alluvium  in,  80. 

Aveline,  Mr.,  on  Caradoc  sandstone,  442. 
Avicula  cygnipes,  A.  in&quivalvis,  318. 

papyracea,  389  ;  A.  sodalis,  336. 

Aviculopecten  sublobatus,  carboniferous,  410. 
Axinm  angulatus,  London  clay,  219. 
Aymestry  limestone,  437. 

BACILLARIA,  fossil  in  tripoli,  25. 

vulgaris  ?,  in  tripoli,  25. 

Bacnlites  anct-ps,  B.  Favjassii,  246. 

Bagshot  sands,  215. 

Bahia  Blanca,  fossil  remains  at,  155. 

Baiae,  Bay  of,  strata  in,  529. 

Bakeweil,  Mr.,  on  cleavage  in  the  Alps,  608. 

Bala,  lower  Silurian  rocks  at,  445. 

Baleena  emarginata,  tympanic  bone  of,  174. 

Balgray,  near  Glasgow,  stumps  of  trees  in  coal,  375. 

Baltic,  brackish  water  strata  on  coast  of,  120. 

Barrande,  M.,  on  Bohemian  Silurian  rocks,  445. 

,  on  primordial  fauna,  447. 

,  on  trilobites,  445. 

Barton  clay  described,  213. 

Barcombe,  chalk-flint  gravel  near,  287. 

Basilosaurus  cetirides,  234. 

Basterot,  M.  de,  on  tertiaries  of  south  of  France,  111. 

Basalt,  6.470. 

,  columnar,  in  the  Eifel,  489. 

,  columnar,  near  Vicenza,  488. 

.  columnar,  of  Giants'  Causeway,  6. 

,  columnar,  structure  of,  487. 

Basset,  term  explained,  56. 

Batrachian,  eggs  of  ?,  in  old  red,  Scotland,  421. 

Bats,  teeth  of,  220. 

Bayfield,  Capt.,  on  fossil  shells  in  Canada,  134. 

,  or  inland  cliffs  in  Gulf  of  St.  Lawrence,  78. 

Bean,  Mr.,  on  Norwich  crag  shells  in  Yorkshire,  156. 

,  on  fossil  shells  from  oolite,  315. 

Beachy  Head,  chalk-cliffs  near,  276. 
Beaumont,  M.  E.  de,  on  rocks  of  Hautes  Alpes,  455. 
,  on  lamination  of  volcanic  rocks,  480. 

,  on  pisolitic  limestone,  237. 

,  on  Swiss  Alps,  585. 


Beaumont,  M.  E.  de,  on  quartz,  68. 

,  on  oolite  formation  in  France,  253. 

,  on  Wealden  island,  282. 

Beck,  Dr.,  cited,  202.  243. 

,  on  graptolites,  445. 

Belemnites  hastatus,  305  ;  B.  mucronatus,  246. 

Puzosianus,  Oxford  clay,  306. 

Bellerophoncostatus,  carboniferous,  411. 

Belosepia  sepioidea.  eocene,  219. 

Bembridge  or  Binstead  beds,  Isle  of  Wight,  194.  209. 

Berenicea  diluviana,  oolite,  308. 

Berger,  Dr.,  on  rocks  altered  by  dikes,  484. 

Bergmann  on  trap,  464. 

Berlin,  tertiary  strata  near,  190. 

Bermuda  Islands,  lagoons  in,  241. 

,  rocks  of,  78. 

Bernese  Alps,  gneiss  in,  621. 

Berthier,  M.,  on  augite  and  hornblende,  4C8. 

Beudant,  M.,  on  Hungary,  549. 

Beyrich,  M.  on  Berlin  tertiaries,  190. 

,  on  North  German  tertiaries,  179. 

Biaritz,  calcareous  cliffs  of,  72. 
Bilin  tripoli,  composed  of  Infusoria,  25. 
Binney,  Mr.,  on  Stigmaria  and  Sigillaria,  370. 
Bird,  bone  of,  in  lower  eocene  beds,  462. 

,  footprints  of,  348. 

,  fossil,  scarcity  of,  462. 

Bischoff,  Prof.,  experiments  on  heat,  601. 

,  on  steam  at  a  high  temperature,  602. 

Blackdown  beds,  equivalent,  of  gault,  252. 
Blainville,  on  number  of  genera  of  mollusca,  28. 
Boase,  Dr.,  cited,  605. 
Boblaye,  M.,  on  inland  cliffs,  73. 

,  cited,  560. 

Bog-iron-ore,  26. 

Bohemia,  Silurian  rocks  of,  454. 

Bolderberg,  in  Belgium,  miocene  or  falunian  strata 

of,  179. 
Bone-bed  of  fish-remains  in  Armagh,  413. 

,  Silurian,  435. 

Bone-beds,  usually  contain  rolled  bones,  458. 
Boom  and  Rupelmonde,  189. 
Bordeaux,  falunian  strata  near,  179. 

,  tertiary  deposits  of,  179. 

Borrowdale,  black-lead  of,  38. 

Bosquet,  M.,  on  Kleyn  Spawen  tertiary  shells,  135. 

,  on  Maestricht  beds,  238. 

Bos  taurus,  tooth  of,  167. 

Boston,  U.  S.,  recent  strata  in  morass,  upraised  and 

bent,  136. 

Bothnia,  Gulf  of,  land  upheaved,  45. 
Bone,  M.,  on  arrangement  of  rocks,  96. 

,  on  fossil  shells  in  Hungary,  549. 

,  on  Carrara  marble,  619. 

,  on  Swiss  Alps,  6'21. 

Bonelli,  on  strata  in  Italy,  112. 
Boulder  formation  in  Canada,  140. 

,  mineral  ingredients  of,  132. 

in  England,  126.  137. 

,  period,  fauna  of,  132. 

Boulders,  129. 

,  striated,  143. 

Boutigny,  M.,  cited,  570. 

Bowen,  Lieut.  A.,  R.N.,  drawings  of  rocks  in  Gulf 

of  St.  Lawrence,  78. 

Bowerbank,  Mr.,  on  fossil  flora  of  Sheppey,  217. 
Bowman,  Mr.,  on  coal-seams,  395. 
Bracklesham  Bay,  characteristic  shells  of,  215. 
Bradford  encrinites,  308. 
Brash,  term,  explained,  81. 
Bravard,  M.,  on  Auvergne  mammalia,  204.  425. 
Brazil,  ossiferous  caves  in,  165. 
Breccia  on  ancient  coast-lines,  73. 
Brickenden,  Captain,  on  Elgin  fossils,  417. 
Brighton,  elephant-bed  of,  288. 
Bristol,  dolomitic  conglomerate  near,  357. 
,  section  of  strata  near,  103. 


INDEX. 


643 


Brocchi,  on  Subapennines,  111.  174. 
Brockedon,  Mr.,  on  black-lead,  38. 
Broderip,  Mr.,  cited,  313. 
Brodie,  Rev.  P.  B  ,  on  fossil  insects,  301.  328. 

,  Mr.  W.  R.,  Purbeck  mammifer  found  by,  296. 

Bromley,  oyster-bed  near,  221. 

Brongniart,  M.  Adolphe,  on  Eocene  flora,  217. 

,  on  flora  of  cretaceous  period,  266. 

,  on  fossil  plants  in  lias,  329. 

,  on  plants  of  bunter-sandstein,  337. 

,  on  fossil  fir-cones,,  366. 

— — ,  on  Permian  flora,  360. 

,  on  sigillaria,  369. 

— — ,  on  asterophylites,  369. 

,  on  stigmaria,  370. 

,  on  age  of  acrogens,  374. 

Brongniart,  M.  Alex.,  on  Paris  tertiaries,  110. 

,  on  eocene  formation,  223. 

,  on  shells  of  nummulitic  formation,  231. 

,  on  coal-mine  near  Lyons,  377. 

Brontes  flabellifer,  Devonian,  428. 
Brora,  oolitic  coal-formation,  315. 

,  granite  near,  589. 

Brown-coal  of  Germany,  age  of,  181.  192. 
Brown,  Mr.  Richard,  on  stigmariae,  370. 
— — ,  on  coal-formation,  370. 

,  on  Cape  Breton  coal  field,  383. 

,  on  carboniferous  rain-prints,  384. 

Buch,  Von.    See  Von  Buch. 

Buckland,  Dr.,  on  cave  at  Kirkdale,  161. 

,  on  coal  plants,  375. 

,  on  coprolites  in  chalk,  242. 

,  on  fish  of  lias,  323. 

— ,  on  glaciers  in  Caernarvonshire,  137. 

,  on  oyster-bed  near  Bromley,  221. 

,  on  parallel  roads,  87. 

,  on  term  Poikilitic,  334. 

,  on  saurians  of  lias,  325. 

,  on  sudden  destruction  of  saurians,  387. 

.cited,  162.294.298.310,311. 

Buddie,  Mr.,  on  creeps  in  coal-mines,  50. 

,  on  ancient  river-channels  of  coal-period,  399. 

Buist,  Dr.  G.,  on  saltness  of  Red  Sea,  347. 
Bulimus  ellipticus,  210 ;  B.  lubricus,  30. 
Bunbury,   Mr.  C.  J.  F.,  on  plants  of  oolitic  coal- 
field, 332  -,  on  fossil  plants  in  Madeira,  519. 
Bunsen,  Prof.,  on  palagonite,  474. 
Bunter-sandstein,  337. 
Buprestisf  elytron  of,  in  oolite,  310. 
Burmeister,  on  trilobites,  445. 
Burnes,  Sir  A.,  cited,  346. 

CAIRO,  exavations  at,  3. 

Catamites  cannteformis,  C.  Suchowii,  367- 

Calamites  near  Pictou,  378. 

Calamite,  root-end  of,  367 ;  structure  of,  368. 

Calamophyllia  radiala,  oolite,  307. 

Calamodendron,  368. 

Calcaire  grossier,  227. 

siliceux,  226. 

Calcareous  rocks,  12. 
Calcarina  rarispina,  eocene,  228. 
Calceola  sandalina,  Devonian,  428. 
Caldcleugh,  Mr.,  cited,  525. 
Caldera  of  Palma,  498.  to  512. 
California,  auriferous  gravel  of,  637. 
Calymene  Blnmenbachii,  Wenlock,  440. 
Cambrian  group,  451. 

,  lowest  fossiliferous  beds  of,  453. 

rocks  of  Sweden,  455. 

rocks  of  United  States,  455. 

volcanic  rocks,  564. 

Campagna  di  Roma,  tuffs  of,  535. 
Campophyllumflexuosum,  Devonian,  407. 
Canada,  shells  in  drift  of,  140. 
Cantal,  freshwater  formation  of,  205.  558. 
,  igneous  rocks  of,  557. 


Cape  Breton,  coal-measures  of,  3S3. 

Cape  Wrath,  granite-veins  in,  573. 

Caiadoc  sandstone,  441. 

Carbonaceous  shale,  314. 

Carbonate  of  lime  scarce  in  metamorphic  rocks,  624. 

in  rocks,  how  tested,  12. 

Carboniferous  group,  361. 

flora,  363-  373. 

limestone  of  North  America,  414. 

period,  plutonic  rocks  of,  586. 

period,  volcanic  rocks  of,  561. 

reptiles,  400. 

Carclmrodon  heterodon,  tooth  of,  216. 

Cardiocarpon  Ottonis,  Permian,  359. 

Cardi/a  glubosa,  214. ;  C.  planicosta,  215. 

Cardium  porulosur/i,  eocene,  2i>9. 

Cardium  disximile,  C.  striatulum,  302. 

Carne,  Mr.,  on  Cornish  lodes,  629,  630. 

Carrara  marble,  598,  619. 

Caryophyllia  ccespitosa,  bed  of,  in  Sicily,  158. 

Castrogiovanni,  bent  strata  near,  58. 

Catalonia,  volcanic  region  of,  535. 

Catenopora  escharoides,  Wenlock,  439. 

Catillus  Lamarckii,  chalk,  248. 

Caulopteris  prirrusva,  coal,  364. 

Cautley,  Sir  Proby,  on  Sewalik  hills,  183. 

Caves  in  Europe,  161. 

at  Kirkdale,  161. 

in  Sicily,  160. 

in  Australia,  162. 

Central  France,  Upper  Eocene  of,  195. 

Cephalaspes  Lyellii,  old  red,  419. 

Ceratites  nodosus,  triassic,  336. 

Ccrilhium  cinctum,  30 ;  C.  concavum,  21 2. 

elegans,  C.  plicalum,  194  ;  C.  melanoides,  221 . 

Cervus  alces,  tooth  of,  167. 

Cestracion  Phillippi  (recent),  jaw  of,  250. 

Chalk,  or  cretaceous  beds,  237- 

,  pinnacle  of,  near  Sherringham,  135. 

of  Faxoe,  239. 

,  white,  fossils  of,  26.  24G. 

,  White,  section  of,  240. 

,  white,  extent  and  origin  of,  241. 

,  white,  animal  origin  of,  242. 

,  pebbles  in,  242. 

,  difference  of,  in  North  and  South  Europe,  253. 

Chalk  cliffs,  inland,  on  Seine,  269. 

,  needles  of,  in  Normandy,  271. 

flints,  bed  of,  near  Barcombe,  287. 

Chama  squamosa,  eocene,  213. 

Chambers,  Mr.,  on  Glen  Roy,  88. 

Chamisso,  cited,  243. 

Chara  elastica   (recent),   C.  medicaginula,  32;    C. 
tuberculata,  210. 

Chara,  in  freshwater  strata,  31. 

,  in  flints  of  Cantal,  206. 

,  in  Eo  ene  strata  of  France,  195. 

,  in  Purbeck  beds,  296. 

Charlesworth,  Mr.  E.,on  Crag,  169. 

,  on  Stonesfield  mammifer,  461. 

Charpentier,  M.,  on  Alpine  glaciers,  147.  150. 

Cheirotherium,  footprints  of,  339.  401. 

Chelonian,  footsteps  of,  417. 

Chemical  and  mechanical  deposits,  33. 

Chiastolite-slate,  597. 

Chili,  eaithquake  in,  61. 

,  gold-mines  in,  472. 

Chiloe,  rocks  drifted  from  Andes  to,  151. 

Chimtera  monstrosa  (recent),  323. 

Chlorite-schist,  8.  596. 

Christiania,  dike  near,  483. 

,  passage  of  granite  into  trap-rocks  at,  570. 

,  granite  near,  575. 

,  gneiss  near,  575. 

,  intrusion  of  granite  into  beds  near,  575. 

Chronological  groups,  103. 

table  of  fossiliferous  strata,  105. 

TT  2 


644 


INDEX. 


Ciiaris  coronata,  coral  -rug,  305. 
Cinder-bed,  Purbeck,  295. 
Cladocora  stellaria,  pliocene,  158. 
Classification  of  rocks  and  strnta,  2.  10.  104. 
Claiborne,  marine  shells  of,  233. 
Clausen,  Mr.,  on  Brazil  caves,  165. 
Clawilia  bfdcns,  Rhine  valley,  30. 
Clavulina  conugata,  eocene,  228. 
Clay,  defined,  11. 
Clay-slate,  8.  596. 
Clay -ironstone,  389. 
Clays,  plastic,  2*0. 
Cleavage  of  rocks,  608.  611. 
Climate  of  drift-period,  146. 

of  coal-period,  399. 

Clinkstone,  or  phonolite,  476. 

Clinton  group,  Silurian,  United  States,  449. 

Clymenia  linear  is,  Devonian,  425. 

Coal,  at  Brownsville,  Pennsylvania,  view  of,  397. 

.  conversion  of,  into  lignite,  398. 

,  how  formed,  375. 

insects  in,  388. 

measures,  361,  362. 

mine,  near  Lyons,  377. 

,  Nova  Scotia,  time  required  for  its  growth,  386, 

,  oolitic  at  Brora,  315. 

period,  climate  of,  399. 

—  pipes,  danger  of,  376. 

seams,  continuity  of,  398. 

- strata,  footprints  of  reptiles  in,  <?01. 

,  zigzag  flexures  of,  near  Mons,  53. 
Coal-field  at  Burdiehouse,  389. 

,  oolitic,  of  Richmond,  Virginia,  331. 

of  Ashby-de-la-Zoucb.,69. 

of  Yorkshire,  fossils  of,  389. 

,  United  States,  diagram  of,  392. 

Coalbrook  Dale,  beetles  in  coal  of,  388. 

,  fossil  cones  in,  366. 

,  coal-measures  of,  388. 

,  faults  in,  62. 

Cochliodus  contortits,  teeth  of,  413. 
Cockfield  Fell,  rocks  altered  by  dikes,  485. 
Ccelacitnthus  granulattis,  scale  of,  357. 
Ccelorhynchus,  sword  of,  216. 
Colchester,  Mr.,  on  mammalia  at  Kyson,  2~0. 
Colour  in  shells  of  mountain-limestone,  410. 
Columbia,  Vinegar  River  of,  225. 
C6me,  ravine  in  lava  of,  555. 
Concretionary  structure,  37- 
Condensation  of  rock-material,  38.     . 
Cone  of  a  pine,  Purbeck,  301. 
Cones  in  Val  di  Noto,  492. 

and  craters,  465. 

and  craters,  absence  of,  in  England,  6. 

Conglomerate,  or  pudding-stone,  11.  47. 

dolomitic,  357. 

Coniferous  trees,  fossil,  371. 
Connecticut,  valley  of  the,  348. 

beds,  antiquity  of,  351 . 

Conrad,  Mr.,  on  cretaceous  rocks,  256. 
Consolidation  of  strata,  33. 
Conocephalus  strialus,  Cambrian.  454. 
Connlaria  ornafa,  Devonian,  427. 
Conus  deperditus,  eocene,  217. 
Conybeare,  Mr.,  cited,  64.  69.  275.  319. 

,  on  Plesiosaurus,  324. 

,  on  oolite  and  lias,  330. 

,  on  term  Poikilitic,  334. 

,  on  crocodiles,  218. 

Cook,  Cant.,  on  Fucus  giganteus,  243. 
Copr elites  in  chalk,  242. 
Coralline  crag,  fossils  in,  J71. 
Coral  islands  ;md  reefs,  34.  46. 

rag  of  oolite,  303. 

Corals,  Devonian,  geographical  distribution  of,  432. 
of  Devonian  system,  42G. 


Corals  of  Devonian  strata  in  United  States,  431. 

in  Wenlock  formation,  439. 

Corals,  neozoic  type  of,  407. 

,  paleozoic  type  of,  407. 

Corbula  alata,  Purbeck,  264. 

pisum,  eocene,  194. 

Corinth,  corrosion  of  rocks  by  gases  near,  602. 

Cornbrash  of  lower  oolite,  306. 

Cornean,  or  aphanite,  476. 

Cornwall,  clay  in,  12  ;  granite-veins  in,  574.  600. 

,  mineral-veins  in,  628.  630. 

,  tin  of,  newer  than  Irish  copper,  636. 

Cotta,  Dr.  B.,  on  granite  in  Saxony,  589. 
Crag,  coralline,  fossils  in,  171. 

,  comparison  of  faluns  and,  178. 

,  fluvio-marine,  Norwich,  155. 

Crags  of  Suffolk,  red  and  coralline,  111.  169. 
Craigleith  fossil  trees,  40. 

quarry,  slanting  tree  in,  379. 

Crania,  attached  to  Echinus,  23. 

Paritiensis.  chalk,  247. 

Crassa'ella  sulcata,  eocene,  214. 
Crassina  Omalii,  coralline  crag,  172. 
Crater  of  Island  of  St.  Paul,  513. 
Creeps  in  coal-mines  described,  52. 
Credneria  in  quadersandstein,  207. 
Cretaceous  rocks  of  Pyrenees,  585. 

group,  235. 

group,  flora  of,  266. 

strata  in  South  America  and  India,  256. 

.  period,  plutonic  rocks  of,  585. 

volcanic  rocks,  560. 

rocks  in  United  States,  255. 

,  lower,  257. 

Crinoi.ls,  Silurian,  440. 

Cr (stellar ia  rotitlata,  chalk,  26. 

Crocodiles  near  Cuba,  326. 

Croizet,  M.,  on  Auvergne  fossil  mammalia,  204. 

Cromer,  contorted  drift  near,  135. 

Crop  out,  term  explained,  55. 

Crust  of  earth  defi"ed,  2. 

Crystalline  limestone,  354. 

rocks,  erroneously  termed  primitive,  9- 

—  rocks,  foliation  of,  613. 

schists  defined,  7. 

Curral,  valley  in  Madeira,  how  formed,  520. 

Curved  strata,  47.  49.  136. 

Cutch,  Runn  of,  346. 

Cuvier,  M.,  on  eocene  formation,  223. 

,  on  Amphitherium,  312. 

,  on  tertiary  strata  near  Paris,  110. 

,  on  fossils  of  Montmartre,  224,  225. 

Cyathea  glauca  (recent),  365. 

Cyathina  Buwerbankii,  gault,  407. 

Cyathocrinites  planus,  carboniferous,  409. 

Cyatkociinus  caryocrinoides,  409. 

Cyathophyllum  flexuosum,  407;  C.  ceespilosum,  42C  ; 

C.  turbinatum,  439. 

Cycatieoidea  megalophylla,  Purbeck,  297. 
Cycadiles  comptus,  oolite,  315. 
Cyclas  amnica,  133  :  C.  obovata,  28. 
Cyclopteris  Hibernica,  Devonian,  418. 
Cyclopian  Islands  in  Sicily,  527- 
Cyclostoma  elegans,  pleistocene,  30. 
Cylindn'tes  acutus,  oolite,  309. 
Cyprcea  coccinelloides,  red  crag,  171. 
Cypridttt  Lower  Purbecks,  297;  Middle   Fnrbecks, 

295  ;  Upper  Purbecks,  294  ;  Wealien,  V63. 
Cypridina  scrrato-striata,  Devonian,  42-i. 
Cypn's  f  inflata,  coal,  387. 
Cypris  in  Lias,  328. 

in  Wealden,  263. 

in  marl  of  Auvergne.  200. 

in  Purbeck  bed?,  294,  2S5.  297. 

Cyrena    consobrina,   28 ;    C.   cuneiformis,   221  ;    C 

scmistrinia,  194. 


INDEX. 


645 


Cystides  in  Silurian  rocks,  444. 
Cytherella,  chalk,  26. 

D.-IDOXYLOV,  coal-plant,  372. 

Dana,  Mr.,  on  crystalline  limestone,  604. 

,  on  coral-reef  in  Sandwich  Islands,  242. 

,  on  volcanos  of  Sandwich  Islands,  493.  497.  551. 

Dapedius  mondifer,  scales  of,  322. 
Dupfinogene  cinnamomi folia,  192. 
"Dartmoor,  granite  of,  586. 
Darwin,  Mr.  on  foliation,  613. 

.cited,  242.  243. 

,  on  boulders  and  glaciers  in  S.  America,  144. 

,  on  cleavage  in  South  America,  613. 

,  on  coral-islands  of  Pacific,  242. 

,  on  dike  in  St.  Helena,  533. 

,  on  habits  of  ostrich,  3.M. 

,  on  fossils  in  South  America,  155. 

,  on  Fucus  giganteus,  243. 

,  on  gradual  rise  of  part  of  South  America,  46. 

,  on  lamination  of  volcanic  rocks,  61G. 

• ,  on  parallel  roads,  87.  88. 

— — ,  ou  plutonic  rocks  of  Andes,  ?83. 
— ,  on  recent  strata  near  Lima,  121. 

,  on  saurians  in  Galapagos  Islands,  326. 

,  on  sinking  of  coral-reefs,  46. 

• ,  on  Welsh  glaciers,  137. 

Daubeny,  Dr.,  on  the  Solfatara,  602. 

,  on  volcanos  in  Auvergne,  557. 

Davidson,  Mr.,  on  liassic  spirifers,  319. 

Dawson,  Mr.,  on  coal-plants,  382. 

Dax,  inland  cliff  at,  72. 

Dean,  forest  of,  coal  in,  399. 

Deane,  Dr.,  on  footprints,  349. 

Decken,  M.  von,  on  granite-veins  in  Cornwall,  445; 

on  reptiles  in  Saarbriick  coal-field,  400. 
De  Koninck,  M.,  cited,  185.  189. 

,  on  Kleyn  Spawen  tertiaries,  185. 

De  la  Beche,  Sir  H.,  cited,  294.  298.  328. 

,  on  Carrara  marbles,  619. 

,  on  clay-beds,  330. 

,  on  clay  ironstone,  389. 

,  on  coal-measures  near  Swansea,  362. 

,  on  fossil  trees,  South  Wales,  376. 

,  on  granite  of  Dartmoor,  600. 

,  on  mineral-veins,  631.  633.  637. 

,  on  term  supracretaceous,  103. 

,  on  trap  of  new  red  sandstone  period,  561. 

Delesse,  M.,  analysis  of  minerals,  479. 
— ,  on  basalt,  470. 

,  on  hypersthene  rock,  477. 

— — ,  on  hypogene  limestone,  604. 

,  on  laterite  of  Antrim,  475. 

,  on  pyroxene,  469.  '''"'• 

,  on  serpentine,  478. 

Deluge,  4. 

Denudation  explained,  66. 

of  the  Weald  Valley,  272. 

,  terraces  of,  in  Sicily,  75. 

of  volcanic  craters,  508.  511. 

Derbyshire,  lead-veins  of,  635. 
Deshayes,  M.,  identification  of  shells,  185. 

,  on  fossil  shells  in  Hungary,  549. 

• •,  on  lower  eocene  shells,  229. ' 

,  on  tertiary  classification,  116. 

,  on  upper  marine  strata.  185. 

Desmarest,  on  trappean  rocks,  91. 
Desnoyers,  M.,  on  Faluns  of  Touraine,  111. 
Desor,  M.,  on  glacial  fauna  in  North  America,  140. 
Devonian  system,  term  explained,  423. 

series  of  North  Devon,  424. 

series  of  Russia,  429. 

series  of  United  States,  430. 

De  Wael,  M.,  on  Antwerp  strata,  174. 
Diagonal,  or  crosj  stratification,  16. 
Diatomacece  in  tripoli,  25. 
Dicer  as  arietinum,  205. 


Dicotyledonous  leaves  in  lower  chalk,  267. 
Didelphys  A%arce  (recent),  jaw  of,  312. 
Didymograpsus  geminns,  D.  Murchisoni,  446. 
Dike  in  St.  Helena,  533. 
Dikelocephalus  Minnesotcnsis,  457. 
Dikes  at  Palagonia  in  Sicily,  533. 

defined, 6. 

in  Scotland,  481. 

— -  of  Somma,  530. 

,  trappean,  crystalline  in  centre,  480.  482. 

Diluvium,  popular  explanation  of  term,  139. 

Dinornis  of  New  Zealand,  106. 

Dinotherium  giganteum,  skull  of,  177. 

Dinotherium  in  India,  18^. 

Diorite,  or  greenstone,  471.  476. 

Dip,  term  explained,  53.      * 

Diplograpsus  Jolium,  D.  pristis,  446. 

Dirt-bed  of  Purbeck,  298.  301. 

Dolerite,  or  greenstone,  470.  477. 

Dolomite  defined,  13. 

Dolomitic  conglomerate,  357. 

Domite,  or  earthy  trachyte,  477. 

Done,  M.  B.  de,  on  volcanos  of  Velay,  557. 

Drift,  contorted,  near  Cromer,  135. 

in  Ireland,  138. 

in  Norfolk,  132. 

,  meteorites  in,  152. 

— — ,  northern,  in  Scotland,  131. 

,  northern,  in  North  Wales,  137. 

of  Scandinavia,  North  Germany, and  Russia,  126. 

period,  climate  of,  146. 

period,  subsidence  in,  142. 

shells  in  Canada,  141. 

Dudley  limestone,  439. 

,  shales  of  coal  near,  600. 

Dufrenoy,  M.,  on  granite  of  Pyrenees,  600. 

,  on  Hill  of  Gergovia,  559. 

Dufi',  Mr.  P.,  on  reptile  of  old  red,  416. 
Dunker,  Dr.,  on  Wealden  of  Hanover,  265. 
Dura  Den,  yellow  sandstone  of,  416. 
Disaster  ringens,  inferior  oolite,  316. 


ECHINODERMS  of  coralline  crag,  173. 
Echinosphterites  Balthicus,  444. 
Echinus,  with  Crania  attached,  23. 
Egerton,  Mr.,  on  fossils  of  Southern  India,  256. 
Egerton,  Sir  P.,  on  fish  of  marl-slate,  3^6. 

,  on  fossil  fish  of  Connecticut  beds,  351- 

,  on  fossils  of  Isle  of  Wight,  213. 

,  on  saurians  and  fish  in  new  red  sandstone.  338. 

,  on  Ichthyosaurus,  323. 

Egg-like  bodies  in  Old  Red  Sandstone,  42K 
Eggs,  fossil,  of  snake,  1V6. 
Ehrenberg,  Prof.,  on  bog-iron-ore,  26. 

,  ou  infusoria,  25. 

— — ,  on  Silurian  foraminifera,  448. 
Eifel,  volcanos  of,  543 — 548. 
Elephant-bed,  Brighton,  i.88. 
Elephas  primigenius,  tooth  of,  166. 
Elgin,  reptile  of  old  red,  found  near,  416. 
Elvans  of  Ireland  and  Cornwall,  637. 

,  term  explained,  587. 

Encrinite,  plate  of,  overgrown  with  Serpula  and 

Bryozoa,  308. 
Encrinite  of  Bradford,  308. 
Encrinus  liiiiformis,  336. 
Eocene:  foraminifera,  228. 

formations,  208. 

formations  in  England,  209. 

granite,  583. 

strata  in  France,  195.  223, 

strata  in  United  States,  232. 

,  term  defined,  116. 

,  upper,  near  Louvain,  Belgium,  177. 

volcanic  rocks,  558. 

Eppelsheim,  Dinotherium  of,  177.  192. 
Equisetaceae  of  coal-period,  367. 

TI    3 


646 


INDEX. 


Equisetites  columnaris,  335. 
Equisetum  of  Virginian  oolite,  332. 

giganteum  of  S.  America,  recent,  367- 

Equ-us  cuballus,  tooth  of,  167. 

Erman  on  meteoric  iron  in  Russia,  152. 

Erratics,  Alpine,  147. 

,  northern  origin  of,  129. 

Eschara  disticha,  chalk,  249. 
Escharina  oceani,  chalk,  249. 
Escher,  M.,  on  boulders  of  Jura,  150. 
Estheria  ?,  Richmond,  U.  S.,  332. 
Etna,  deposits  of,  517. 
Eunomia  radiata,  307. 
Euomphalus  penlagulatus,  411. 
Euphotide,  477. 
Eurite,  569.  597. 

Euritic  porphyry  described,  466. 
Extracrinus  Briareus,  lias,  322. 

FALONS  of  Touraine,  111.  176. 

Faluns,  comparison  of,  and  crag,  178. 

Falnnian  type,  distinctness  of,  from  Eocene,  180. 

Falconer,  Dr.,  on  Sewalik  Hills,  183. 

Falkland  Islands,  88. 

Farnham,  phosphate  of  lime  near,  252. 

Fascicularia  aurantium,  172. 

Fault,  term  explained,  62. 

Faults,  origin  of,  64. 

Favosites  Gothlanrtica,  43!) ;  F.  polymorpha,  426. 

Faxoe,  chalk  of,  239. 

felt's  tigris,  tooth  of,  168. 

Felixstow,  remains  of  cetacea  found  near,  174. 

Felspar,  varieties  of,  457. 

Fenestella  retiformis,  355. 

Ferns  in  coal-measures,  364. 

Fife,  altered  rock  in,  485. 

Fifeshire,  trap-dike  in,  5(  3. 

Fish,  oldest,  in  Upper  Ludlow,  435. 

Fishes,  fossil,  of  Upper  Cretaceous,  250. 

of  Brown-coal,  545. 

of  Old  Red  Sandstone,  419. 

of  Wealden,  263. 

Fissures    filled   with   metallic   matter,   629.      See 
Mineral  veins. 

Fitton,  Dr.,  on  lower  cretaceous  beds,  257. 
,  cited.  261.  294.  298.  304. 

Fleming,  Dr.,  on  scales  offish  in  old  red,  418. 

,  on  trap-rocks  in  coal-field  of  Forth,  561. 

,  on  trap-dike  in  Fifeshire,  562. 

Flints  of  chalk,  11.244. 

Flora,  carboniferous,  363. 

cretaceous,  266. 

of  London  clay,  217. 

,  permian,  359. 

Flotz,  term  explained,  91. 

Flysch,  explanation  of  term,  232. 

Foliation,  term  defined,  613. 

Fontainebleau,  Gres  de,  185.  195. 

Footprint  of  bird,  349. 

Footprints  of  reptiles,  339.  349.  402,  403.  417. 

Foraminifera,  chalk,  26  ;  tertiary,  180.  216.  228.  231 
232  ;  paleozoic,  413.  448. 

Forbes,  Mr.  David,  on  foliation,  614. 

Forbes,  Prof.  E.,  on  Bemtfridge  series,  186.  188. 

,  on  Caradoc  sandstone,  442. 

,  on  Cystideae,  443. 

,  on  Hempstead,  Isle  of  Wight  series,  186,  193. 

,  on  Mull  leaf-bed,  181. 

,  on  shells  in  crag-deposits,  173. 

,  on  cretaceous  fossil  shells,  255. 

,  on  fossils  of  the  faluns,  177. 

,  on  fossils  in  drift  in  South  Ireland,  138. 

,  on  deep- sea  origin  of  Silurian  strata,  459. 

— ,  on  echinoderms  of  coralline  crag,  173. 

,  on  fauna  of  boulder-period,  132. 

,  on  migrations  of   mollusca  in  glacial-perioc 

173. 


'orbes,  E.  on  fo? sils  of  Purbeck  group,  294.  298.  300. 

,  on  strata  at  Atherfield,  258. 

,  on  volcanic  rocks  of  oolite-period,  560. 

,  on  depth  of  animal  life  in  ^Egean,  35.  144. 

,  on  geographical  provinces,  257. 

brbes,  Prof.  James,  on  zones  in  glacier-ice,  613. 

,  on  the  Alps,  150. 

Forchhammer,  on  scratched  limestone,  127. 

'orest,  fossil,  in  Norfolk,  134.  137. 

'orest  marble  of  oolite,  306. 
Forfarshire,  old  red  sandstone  in,  605. 

brmation,  term  defined,  3. 
Fossil  ferns  in  carbonaceous  shale,  315. 
.  footsteps,  337.  339,  340. 
forest  in  Isle  of  Portland,  298. 

forest  in  Nova  Scotia,  379. 

forest  near  Wolverhampton,  377. 

plants  in  wealden,  265. 

remains  in  caves,  160. 

shells  from  Etna,  627  ;  near  Grignon,  227. 

shells  of  Mayence  strata,  191 ;  of  Virginia,  182. 

-  shells,  passim. 

-,  term  defined,  4. 

-  trees  erect,  375. 

wood,  perforated  by  Teredina,  24. 

wood,  petrifaction  of,  39- 

Fossils,  arrangement  of,  in  strata,  5. 

,  freshwater  and  marine,  27. 

in  chalk  at  Faxoe,  239. 

in  faluns  of  Touraine,  177. 

of  chalk  and  greensand,  246.  248. 

•  of  Connecticut  beds,  351. 

of  coralline  crag,  172. 

of  devonian  system,  425. 

of  eocene  strata  in  United  States,  233,  234. 

of  Isle  of  Wight,  209. 

of  lias,  318.  329. 

of  London  clay,  219. 

of  lower  greensand,  259. 

.  of  Ludlow  formation,  438. 

of  Maestricht  beds,  238. 

—  of  mountain  limestone,  407. 

of  new  red  sandstone,  335.  337. 

of  old  red  sandstone,  419. 

of  oolite,  2G6.  302.  309. 

of  Permian  limestone,  356,  357. 

of  Purbeck,  294. 

of  red  crag,  171. 

of  Richmond,  U.  S.,  strata,  332. 

of  Solenhofen,  303. 

of  upper  greensaud,  252. 

of  wealden,  262. 

,  petrifaction  of,  39—43. 

,  test  of  the  age  of  formations,  98. 

Fossiliferous  strata,  tabular  view  of,  460. 

Fournet,  M.,  on  mineral-veins  of  Auvergne,  632. 

,  on  disintegration  of  rocks,  601. 

, ,  on  quartz,  568. 

Fox,  Mr.  R.  W.,  635,  on  Cornish  Iocs,  636. 

Fox,  Rev.  Mr.,  on  extinct  quadrupeds  of  Isle  of 
Wight,  210. 

Freshwater  beds  of  Isle  of  Wight,  209. 

deposits  in  valley  of  Thames,  153. 

.  land-shells  numerous  in,  27. 

Freshwater  formations  of  Auvergne,  198. 

Freshwater    formations,    how    distinguished    from 
marine,  27,  28.  30.  32. 

associated  with  Norfolk  drift,  133. 

Freshwater  shells  in  brown-coal  near  Bonn,  544. 

Fucus  vesiculosus,  33.  243. 

Fulgur  canaliculatus,  182. 

Fuller's  earth  of  oolite,  315. 

Fundy,  Bay  of,  impressions  in  red  mud  of,  348. 

Fungia  patellaris  (recent),  407. 

Fusulinu  cylindrica,  413. 

Fusus  contrarius,  171  ;  F.  quadricustatus,  182. 


INDEX. 


647 


GALAPAGOS  ISLANDS,  animals  of,  326. 

Galeocerdo  latidens,  tooth  of,  216. 

Galerites  albogalerus,  246. 

Gallionella  distans,  G.ferrugmea,  in  tripoli,  25. 

Ganges,  buried  soils  in  delta  of,  387. 

Garnets  in  altered  rock,  484. 

Gases,  subterranean  rocks  altered  by,  602. 

Gault  of  upper  cretaceous,  251. 

Gavarnie,  flexures  of  strata  near,  59. 

Geology  defined,  1. 

Gergovia,  Hill  of,  559. 

Gervillia  anceps,  lower  greensand,  260. 

Giant's  Causeway,  columns  at,  487. 

basalt,  age  of,  181. 

Gibbes,  R.  W.,  cited,  234. 

Girgenti,  limestone  of,  157. 

Glacial  phenomena,  northern,  origin  of,  139. 

Glaciers,  Alpine,  147. 

on  Caernarvonshire  mountains,  137. 

Glasgow,  marine  strata  near,  155. 

Glenroy,  parallel  roads  of,  86. 

Glen  Tilt,  granite  of,  572. 

Glyphceaf  dubia,  coal-measures,  388. 

Gneiss,  altered  by  granite,  575. 

in  Bernese  Alps,  606. 

at  Cape  Wrath,  573. 

near  Christiana,  575. 

described,  595. 

Gold,  age  of,  in  Ireland,  637. 

,  age  of,  in  Ural  Mountains,  638. 

Goldfuss,  Prof.,  on  reptiles  in  coal-field,  401. 

Goniatites  crenistria,  G.  evolutus,  412  ;  G.  Lister i, 
389. 

Gorgonia  mfundibuliformis,  355. 

Go'ppert,  Prof.,  on  beds  of  coal,  363. 

on  petrifaction,  40. 

Gradual  increase  of  strata,  22. 

Graham's  Island,  492.  534. 

Grampians,  old  red  conglomerates  in,  47. 

Granite  described,  7.  565. 

,  passage  of,  into  trap,  570. 

,  porphyritic,  568. 

and  limestone,  junction  of  in  Glen  Tilt,  571. 

,  syenitic,  takose,  and  schorly,  569. 

of  Cornwall  and  Dartmoor,  600. 

of  Swiss  Alps,  620. 

rocks  in  connection  with  mineral-veins,  638. 

of  Saxony,  589. 

,  oldest,  588. 

,  varieties  of,  573. 

veins  in  Cornwall,  574. 

veins  in  Cape  Wrath,  574. 

veins  in  Table  Mountain,  573. 

vein  in  White  Mountains,  580. 

• of  Arran,  age  of,  589. 

near  Christiania,  587. 

dikes  in  Mount  Battock,  573. 

Graphic  granite,  567. 

Graphite,  powder  of,  consolidated  by  pressure,  38. 

Graptolites,  446. 

Graptolithus  Ludensis,  Silurian,  441. 

Grasshopper,  wing  of,  in  coal-measures,  389. 

Grateloup,  M.,  on  fossils  in  chalk,  255. 

Grauwacke,  term  explained,  433. 

Great  (or  Bath)  Oolite,  306. 

Greenland,  sinking  of  coast  of,  46. 

Greensand,  fossils  of,  252. 

,  lower,  257. 

,  upper,  251. 

Greensburg,  Pennsylvania,  footprints  of  reptile  in 

coal-strata  at,  401. 
Greenstone,  471. 

,  dike  of,  in  Arran,  481. 

Grds  de  Beauchamp,  Paris  Basin,  227. 
Greystone,  volcanic  rock,  477. 
Griffiths,  Mr.,  on  geology  of  Ireland,  362. 
Grignon,  fossil  shells  near,  227. 

T  T 


Grit  defined,  11. 

Gryllacris  lithauthraca,  wing  of,  389. 

Gryphtea  coated  with  Serpute,  22. 

arcuata,  G.  incurva,  29.  319. 

columba,  G.  globosa,  248  ;  G.  virgula,  302. 

Gryphite  limestone,  or  lias,  319. 
Guadaloupe,  human  skeleton  of,  121. 
Gunn,  Mrs.,  on  Norwich  flints,  245. 
Gutbier,  Col.  von,  on  Permian  flora,  359. 
Gyrolepis  tenuistriatus,  scale  of,  338. 
Gypseous  eocene  marls,  224,  225. 
Gypsum  denned,  13. 

HALL,  Sir  Jas.,  experiments  on  fused  minerals,  532. 

,  on  curved  strata,  48. 

,  Capt.  B.,  cited,  480.  527.  573. 

Halt/sites  calenulalus,  Silurian,  439. 

Hamilton,  Sir  W.,  on  eruption  of  Vesuvius,  537. 

Hamites  spinfger,  gault,  252. 

Harris,  Major,  on  salt  lake  in  Ethiopia,  346. 

Hartung,  Mr.  G.,  on  Teneriffe,  515. 

,  on  Madeira,  518.  522. 


Hartz,  bunter-sandstein  of,  337. 
Hastings,  Lady,  fossils  collected  by,  212. 
Hastings  sand,  263,  264. 
Hautes  Alpes,  rocks  of,  585. 
Haiiy  cited,  467. 

Hawkshaw,  Mr.,  on  fossil  trees  in  coal,  375. 
Hayes,  Mr.  T.  L.,  on  icebergs,  128. 
Headon  Hill  sands  described,  213. 

series  of  Isle  of  Wight  described,  211. 

Hebert,  M.,  on  upper  eocene  beds,  185. 

,  on  age  of  Kleyn  Spawen  beds,  185. 

,  on  pisolitic  limestone,  237. 

Hebrides,  dikes  of  trap  in,  481. 

Heidelberg,  varieties  of  granite  near,  573. 

Heliolites  porosa,  426. 

Helix  labyrinthica,  212  ;  H.  occlusa,  210  j  H.  plebeia, 

125  ;  H.  Turonensis,  30. 
Hemicidaris  Purbeckensis,  295. 
Hemipneustes  radiatus,  239. 
Hemitelites  Brownii,  315. 
Hempstead  beds,  Isle  of  Wight,  186.  193. 
Henfrey,  Mr.  A.,  on  food  of  Mastodon,  145. 
Henslow,  Prof.,  on  fossil  cetacea  in  Suffolk,  174. 

,  on  fossil  forests,  298. 

,  on  altered  rock  near  Plas  Newydd,  484. 

Herschell,  Sir  J.,  on  slaty  cleavage,  609. 
Hertfordshire  pudding-stone,  35. 
Hesse  Cassel,  sands  of,  187. 
Heteroceral  fish,  tail  of,  356. 
Hibbert,  Dr.,  on  volcanic  rocks,  547.  557. 

,  on  coal-field  at  Burdiehouse,  389. 

High  Teesdale,  garnets  in  altered  rock  at,  484. 
Hildburghausen,  footprints  of  reptile  at,  337.  339. 
Himalaya,  tertiary  mammalia  of,  183. 

,  elevated  fossiliferous  rocks  in,  4. 

Hippopodium  ponderosum,  lias,  320. 
Hippopotamus,  tooth  of,  167. 
Hippurites  organisans,  chalk,  254. 
Hippurite  limestone,  254. 
Hitchcock,  Prof.,  on  footprints,  348. 
Hoffmann,  Mr.,  on  Lipari  Islands,  cited,  602. 

,  on  cave  near  Palermo,  74. 

,  on  Carrara  marble,  619. 

Hooghley  River,  analysis  of  water  of,  41. 
Holoptychius  nobilissimus,  scale  of,  418. 

Hibberti,  tooth  of,  400. 

Homalonotus  armaitis,  429.) 

delphinocephalus,  441. 

Homoceral  fish,  tail  of,  356. 
Hopkins,  Mr.,  on  fractures  in  Weald,  281. 
Horizontal  strata,  upheaval  of,  45. 
Horizontality  of  strata,  15. 

of  roads  of  Lochaber,  88. 

Hornblende,  467. 

rock,  or  amphibolite,  477.  597. 

4 


648 


INDEX. 


Hornblende-schist,  595.  603. 
Homer,  Mr.,  on  geology  of  Eifel,  543. 

on  Holoptychius,  400. 

Homes,  Dr.,  on  shells  of  Vienna  tertiary  basin,  180. 
Hubbard,  Prof.,  on  granite-vein   in  White  Moun- 
tains, 380. 

Hugi,  M.,  on  Swiss  Alps,  621. 
Humboldt,  on  uniform  character  of  rocks,  623. 
Hungary,  trachyte  of,  471. 

,  volcanic  rocks  of,  549. 

Hunt,  Mr.,  experiments  on  clay-ironstone,  389. 

Hutton,  opinions  of,  60. 

Huttonian  theory,  92. 

Hycena  spelcea,  tooth  of,  168. 

Hybodus  reliculatus,  tooth  and  ray  of,  322. 

plicatilis,  teeth  of,  338. 

Hymenocaris  vermicauda,  452. 
Hypersthene  rock,  477. 
Hypogene,  term  defined,  9. 

rocks,  mineral  character  of,  622. 

or  metamorphic  limestone,  596. 

IBBETSON,  Capt.,  on  chalk,  Isle  of  Wight,  251. 
Ice,  rocks  drifted  by,  1*7. 
Icebergs,  stranding  of,  136.  144. 

,  magnitude  of,  128. 

Iceland,  icebergs  drifted  to,  144. 
Ichthyolites  of  old  red  sandstone,  423. 
Ichthyosaurus  ccmmunis,  skeleton  of,  324  ;   paddle 

of,  325. 
Igneous  rocks,  6. 

of  Siebengebirge  and  Westerwald,  545. 

of  Val  di  Noto,  492. 

Iguarrodon,  notice  of  the,  261.  263. 
Iguanodon  Mantelli,  teeth  of,  262. 
India,  cretaceous  system  in,  256. 
-^,  freshwater  deposits  of,  183. 

,  oolitic  formation  in,  333. 

Indusial  limestone,  Auvergne,  201. 

Inferior  oolite,  315. 

Infusoria  in  tripoli,  24. 

Inland  sea-cliffs  in  South  of  England,  71. 

Inoceramus  Lamarckii,  chalk,  248. 

Insect,  wing  of  neuropterous,  329. 

Insects  in  coal,  388. 

in  lias,  328. 

— —  in  oolite,  310. 

in  Purbeck  beds,  301. 

Invertebrate  animals,  period  of,  457. 
Ireland,  coal  strata  of,  362. 

,  Devonian  plants  of,  418. 

,  drift  in,  138. 

Isastrcea  oblonga,  I.  Ttsburiensis,  302. 
Ischia,  volcanic  cones  in,  529. 

,  post-pliocene  strata  of,  118. 

Isle  of  Wight,  freshwater  beds  of,  211. 
Isomorphism,  theory  of,  468. 

JACKSON,  Dr.  C.  T.,  analysis  of  fossil  bones,  145. 
James,  Capt.,  on  fossils  in  drift,  South  Ireland,  130. 
Java,  stream  of  sulphureous  water,  224. 

,  volcanos  of,  496. 

Jobert,  M.,  on  Hill  of  Gergovia,  559. 

Joints,  608. 

Jorullo,  lava-stream  of,  580. 

Junghuhn,  Dr.,  on  Javanese  volcanos,  496. 

Jura,  alpine  blocks  on,  149. 

limestone,  304. 

,  structure  of,  55. 

KANGAROO,  fossil  and  recent,  jaws  figured,  163. 
Kaup,  Prof.,  on  footprints  of  Cheir other ium,  339. 
Kaye,  Mr.,  on  fossils  of  Southern  India,  256. 
Keeling  Island,  fragment  of  greenstone  in,  243. 
Keilhau,  Prof.,  cited,  587.  600. 

,  on  dike  of  greenstone,  482. 

,  on  foliation,  614. 


Keilhau,  on  gneiss  near  Chvistiania,  575. 

,  on  granite,  577. 

Kelloway  rock,  34. 

Kentish  chalk,  sandgalls  in,  82. 

rag,  lower  greensand,  258. 

Keuper,  the,  335. 

Kilauea,  volcanic  crater  of,  494. 

Killas  in  granite  of  Cornwall,  600. 

Kilkenny  yellow  sandstone,  fossil  plants  of,  418. 

Kimmeridge  clay,  301. 

King,  Dr.,  on  footprints  of  reptile,  402. 

King,  Prof.,  on  Permian  group  and  fossils,  353. 

Kirkdale,  caveat,  161. 

Kyson,  in  Suffolk,  strata  of,  219. 


LABYRINTHODON  JMOERI,  tooth  of,  340,  34 1 . 

pac/iygnatfius,  outline  of,  342. 

Lacustrine  strata  of  Auvergne,  203. 
Lagoons  at  mouth  of  rivers,  33. 

of  Bermuda  Islands,  241. 

Lake  craters  of  Eifel,  545. 

crater  of  Laach,  547. 

Lakes,  deposits  in,  3. 
Lamarck  on  bivalve  mollusca,  29. 
Lamna  elegans,  tooth  of,  eocene,  21G. 
Land,  rising  and  sinking,  45. 
Landenian,  or  lower  eocene  beds,  236. 
Lapidification  of  fossils,  43. 
La  Roche,  estuary  of,  14. 
Laterite,  475.  477. 
Lava,  473. 

current,  Auvergne,  552. 

current,  Madeira,  view  of,  522. 

,  relation  to  trap,  490. 

stream  of  Jorullo,  580. 

streams,  effects  of,  6. 

of  Stromboli,  581. 

Lea,  Mr.,  footprints  of  reptile  discovered  by,  404. 
Leaf-bed,  miocene,  of  Isle  of  Mull,  180. 
in  Madeira,  519. 


Lead-veins  in  Permian  rocks,  638. 

Leda  amygdalotdes,  219 ;    L.  Deshayesiana,  189  ;  L. 

oblonga,  131. 

Lehman  on  classification  of  rocks,  91. 
Leibnitz,  theory  of,  94. 

Leidy,  Dr.,  on  supposed  cetaceans  of  the  chalk,  255. 
Lepidodendra.  365. 
Lepidodendron,  stem  of,  from  Ireland,  418. 

Sternbergii,  366. 

Lepidostrobus  ornatus,  366. 
Lepidotus  gigas,  scales  of,  321. 

Mantelli,  teeth  and  scale  of,  263. 

Leptcena  depressa,  449  ;  //•  Moorei,  320. 
Leptignite,  or  whitestone,  570. 
Lewes,  coomb  near,  278. 
Lias,  318. 

and  oolite,  origin  of,  329. 

at  Lyme  Regis,  325. 

,  fossil  plants  of,  329. 

in  United  States,  331. 

period,  volcanic  rocks  of,  560. 

,  plutonic  rocks  of,  585. 

Liebig,  Prof.,  on  conversion  of  coal  into  Ifgnite,  398. 

,  on  preservation  of  fossil  bones  in  caverns,  162. 

Lima  giganlea,  319  ;  L,  Hoperi,  248. 
Lima,  South  America,  recent  strata  of,  121. 
Limagne  d' Auvergne,  freshwater  formations  of,  198. 
Lhnburg,  or  upper  eocene  strata  of  Belgium,  189. 
Lime    in    solution,  source  of,  42  ;    scarcity  of,  in 

metamorphic  rocks,  624. 
Limestone,  brecciated,  354. 

,  ciystalline,  354. 

— — ,  compact,  355. 

,  fossiliferous,  355. 

,  hippurite,  253. 

,  indusial,  Auvergne,  201. 


INDEX. 


649 


Limestone  of  Jura,  304. 

• ,  magnesian,  353. 

,  mountain,  fossils  of,  407. 

,  primary  or  metamorphic,  596. 

of  Devonian  system  in  Germany,  425. 

Limulus  rotundalus,  coal-measures,  388. 

Lindley,  Dr.,  cited,  2G7. 

Lingula  flags  of  lower  Silurian,  452. 

Lingula  Davisii,  452  ;  L.  Dumortieri,  174  ;  L.Leioisii, 

437. 

Lipari  Islands,  rocks  altered  by  gases  in,  602. 
Lithodomi  in  beaches  of  North  America,  78. 

in  inland  cliffs,  73. 

Lithostrotion  basalti/orme,  L.floriforme,  L.  striatum, 

408. 

Litniies  giganteus,  Silurian,  438. 
Llandeilo  flags,  443. 
Loam  defined,  13.  ', 

Lochabar,  parallel  roads  of,  86. 
Lodes.  See  Mineral  veins,  628. 
Loess  of  valley  of  Rhine,  122. 

,  fossil  land-shells  of,  figured,  125. 

Logan,  Mr.,  on  coal-measures  of  South  Wales,  363. 

,  on  footprints  in  Potsdam  sandstone,  456. 

-— ,  on  fossil  forest  in  Nova  Scotia,  386. 

,  on  lower  Silurian  rocks  of  Canada,  450. 

London  clav,  217. 

Lonsdale,  Mr.,  cited,  159;  on  corals,  183. 

— • ,  on  corals  of  Normandy,  178. 

,  on  fossils  in  white  chalk,  26. 

,  on  old  red  sandstone  of  South  Devon,  423. 

,  on  Stonefield  slate,  310. 

Lonsdaleiafloriformis,  carboniferous,  408. 

Louvain,  eocene  strata  near,  189. 

Loven  on  shells  of  Norway,  120. 

Lucina  serrata,  eocene,  '217. 

Ludlow  formation,  434. 

Lund,  cited,  165. 

Lycett,  Mr.,  on  shells  of  oolite,  310. 

Lycopodium  densum  (recent),  366. 

Lyme  Regis,  lias  at,  328. 

Lym-Fiord  invaded  by  the  sea,  33. 

,  kelp  in,  243. 

Lymncen  caudata,  212 ;  L.  longiscata,  29.  210. 
Lyons,  coal-mine  near,  377. 

MACACVS,  tooth  of,  Eocene,  220. 
M' Andrew,  Mr.,  on   scarcity  of  fish-bones  on  sea- 
bottom,  459. 

MacCulloch,  Dr.,  on  age  of  Arran  granite,  590. 
— ,  on  altered  rock  in  Fife,  485. 

on  basaltic  columns  in  Skye,  487. 

on  denudation,  67. 

on  granite  of  Aberdeenshire,  570. 

on  hornblende-schist,  603. 

on  igneous  rocks  of  Scotland,  492. 

on  Isle  of  Skye,  36. 

on  overlying  rocks,  8. 

— ,  on  parallel  roads,  87. 

,  on  trap- vein  in  Argyleshire,  481. 

Maclaren,  Mr.,  on  erratic  blocks  in  Pent'ands,  132. 
Maclure,  Dr.,  on  volcanos  in  Catalonia,  536. 
Maclurea  Logani.  Silurian,  450. 
Macropus  atlas,  163  ;  jaw  of,  163 ;  tooth  of,  164. 

major  (recent),  jaw  of,  163. 

Madeira,  structure  of,  515—522. 

• ,  trachyte  overlying  basalt  in,  526. 

• — ; — ,  view  of  dike  in  inland  valley  in,  480. 

Maestricht  beds,  238. 

Magnesian  limestone,  concretionary  structure  of,  37. 

defined,  13. 

groups,  353. 

Maidstone,  fossils  in  white  chalk  of,  251. 
Mammalia,  extinct,  above  drift  in  United  States,  144. 

,  extinct,  of  basin  of  Mississippi,  122. 

,  fossil  teeth  of,  167. 

Mammat,  Mr.,  cited,  69. 


Mammifer  in  Purbcck  beds.  296.  461. 

in  Stonesfield  oolite,  312. 

in  trias  near  Stuttgart,  342. 

Mammoth,  tooth  of,  166. 

Mansfield  in  Thuringia,  Permian  formation  at,  359, 

Mantell,  Dr.,  cited,  243.  263.  265.  287. 

,  on  belemnite,  306. 

,  on  chalk-flints,  287. 

,  on  Brighton  elephant-bed,  288. 

,  on  freshwater  beds  of  Isle  of  Wight,  210. 

,  on  iguanodon,  261. 

,  on  wealden  group,  260.  287. 

,  on  reptile  in  old  red,  417.  596. 

Mantellia  megalophylla,  Purbeck,  297. 
Map  to  illustrate  denudation  of  Weald,  273. 

of  eocene  beds  of  Central  France,  196. 

Marble  defined,  12. 
Marl  defined,  13. 

in  Lake  Superior,  36. 

,  red  and  green  in  England,  337. 

Marl-slate  defined,  13. 
Marsupites  Mille.ri,  chalk,  246. 
Martin,  Mr.,  cited,  281. 

,  on  cross  fractures  in  chalk,  275. 

Martins,  Mr.  C.,  on  glaciers  of  Spitzbergen,  143. 

Massachusetts,  plumbago  in,  604. 

Mastodon  angustidens,  tooth  of,  166. 

Mastodon  giganteus,  in  United  States,  144. 

Mastodonsaurus,  tooth  of,  340. 

Mayence  basin  tertiaries,  191. 

May  Hill,  Silurian  strata  of,  435. 

Mediterranean  and  Red  Sea,  distinct  species  in,  100. 

.,  deposits  forming  in,  100. 

Megalodon  cucullatus,  427. 

Megatherium,  tooth  of,  S.  America,  168. 

M.  lania  inquinata,  29.  221 ;  M.  turriltssima,  209. 

Melanopsis  buccinoidea  (recent),  29. 

Melaphyre,  or  black  porphyry,  477. 

Menai  Straits,  marine  shells  in  drift,  137. 

Mendips,  denudation  in,  68. 

Mersey,  in  Kent,  ancient  channel  of,  120. 

Metalliferous  veins.    See  Mineral  veins. 

Metals,  supposed  relative  ages  of,  636. 

Metamorpbic  rocks,  594. 

,  defined,  8. 

,  less  calcareous  than  fossiliferous  rocks,  6!i3. 

,  order  of  succession  of,  622. 

,  glossary  of,  597. 

strata,  origin  of,  598. 

structure,  origin  of,  603. 

Meteorites  in  drift,  152. 

Mexico,  lamination  of  volcanic  rocks  in,  612. 

Meyer,  M.  H.  von,  cited,  154. 

,  on  reptile  in  coal,  401. 

,  on  sandstone  of  the  Vosges.  337. 

,  on  Wealden  of  Hanover  and  Westphalia,  265. 

Mica-schist,  590. 

Micaceous  sandstone,  origin  of,  14. 

Micraster  cor-angumum,  chalk,  246. 

Microconchus  carbonarius,  carboniferous,  387. 

Microlestes  antiquus,  teeth  of,  triassic  mammifer,  342. 

Miller,  Mr.  H.,  on  origin  of  rock-salt,  346. 

,  on  old  red  sandstone,  416.  422. 

,  on  fossil  trees  of  coal  near  Edinburgh,  379. 

Minchinhampton,  fossil  shells  at,  309. 
Mineral  character  of  aqueous  rocks,  10.  97. 

composition,  test  of  age  oT  volcanic  rocks,  525. 

springs,  connected  with  mineral-veins,  635. 

veins  and  faults,  626.  628. 

veins  of  different  ages,  628.  ; 

veins,  pebbles  in,  6.50. 

—  veins,  various  forms  of,  627. 

veins  near  granite,  632. 

Mineralization  of  organic  remains,  38. 
Minerals,  table  of  analyses  of  simple,  479. 
Miocene  faluns  of  the  Loire,  176. 
formation,  176. 


650 


INDEX. 


Miocene  formation  in  Isle  of  Mull,  180. 

in  United  States,  181. 

,  (lower)  strata  of  Isle  of  Wight,  186. 

mammalia  of  Sewalik  Hills,  183. 

of  the  Bolderberg,  179. 

period,  volcanic  rocks  of,  543. 

,  term  defined,  1 16. 

Mississippi,  fluviatile  strata  and  delta  of,  3.  122,  123. 
Mitchell,  Sir  T.,  on  Australian  caves,  163. 
Mitscherlich,  Prof.,  on  augite  and  hornblende,  468. 

,  on  mineral  composition  of  Somma,  530. 

Mitrascabra,  Barton  clay,  214. 

Modiola  acuminuta,  Permian,  354. 

Modon,  lithodomi  in  cliff  at,  73. 

Molasse  of  Switzerland,  180. 

Monkey,  tooth  of,  eocene,  220. 

Mons,  flexures  of  coal  at,  53. 

Mont  Blanc,  talcose  granite  of,  £83. 

Mont  Dor,  Auvergne,  550. 

Montlosier,  M.,  on  Auvergne  volcanos,  555. 

Moraine,  term  explained,  129. 

Moraines  of  glaciers,  148. 

Morea,  inland  sea-cliffs  of,  73. 

,  trap  of,  560. 

Morris,  Mr.,  on  fossils  at  Brentford,  154. 
Morton,  Dr.,  on  cretaceous  rocks,  255. 
Morven,  basaltic  columns  in,  487. 
Mosasaurus  Campert,js.'ws  of,  from  Maestricht,  239. 
Mountain  limestone,  fossils  of,  407. 
Mull,  Isle  of,  Miocene  leaf-bed  of,  180. 
Miinster,  Count,  on  fossils  of  Solenhofen,  303. 
Murchison,  Sir  R.,  cited,  279.  286.  288. 

,  on  eocene  gneiss,  606. 

,  on  volcanic  rocks  of  Italy,  535. 

,  on  new  red  sandstone,  338, 

,  on  age  of  Alps,  232. 

,  on  age  of  gold  in  Russia,  637. 

,  on  erratic  blocks  of  Alps,  151. 

,  on  granite,  587.  589. 

• ,  on  primary  strata  in  Russia,  129. 

,  on  joints  and  cleavage,  608. 

,  on  old  red  sandstone  of  S.  Devon,  423.  425. 

— ,  on  pentamerus,  437. 

— — ,  on  Silurian  strata  of  Shropshire,  563. 

,  on  Swiss  Alps,  621. 

,  on  term  Permian,  353. 

,  on  term  Silurian,  433. 

,  on  tilestones,  434. 

Murchisonia  gracilis,  Silurian,  450. 

Mure*  alveolatus,  red  crag,  171. 

Muschelkalk,  335. 

Myliobates  Edwardsi,  teeth  of,  Bracklesham,  216. 

Mytilus  septifer,  Permian,  354. 

NAGELFLTJH,  or  conglomerate  of  Alps,  180. 
Naples,  post-pliocene  formations  near,  529. 

,  recent  strata  near,  118. 

,  rising  of  land  at,  119. 

Nassa granulata,  red  crag,  171. 
Natica  ( recent),  spawn  of,  421. 

clausa,  131  ;  N.  helicoides,  156. 

Nautilus  centralis,  N.  ziczac,  219 ;  N.  Danicus,  240  : 

N.  plicalus,  259  ;  N.  truncatus,  320. 
Navarino,  lithodomi  found  in  cliff  at,  73. 
Nebraska,  U.  S.,  upper  eocene  of,  207. 
Netker,  M.  L.  A.,  cited,  575. 

,  on  composition  of  cone  of  Somma,  531. 

,  on  granite  in  Arran,  590. 

,  on  granitic  rocks,  576. 

,  on  Swiss  Alps,  621. 

— — ,  terms  granite  "  underlying,"  8. 
Nelson,  Capt.,  drawing  of  Bermuda,  79. 

,  on  chalk  of  Bermuda  Island,  241. 

Neocomian,  or  lower  cretaceous,  257. 

Neozoic  type  of  corals,  407. 

Neptunian  theory,  91. 

Nerin&a  Goodhallii,  N.  hieroglyphica,  304. 


Nerita  conoidea,  N.  Schemidelliana,  229  ;  2V.  coslu- 

lata,  309  ;  N.  granulosa,  30. 
Neritina  cuncava,  212  ;  N.  globulus,  30. 
Newcastle  coal-field,  great  faults  in,  64. 
Newcastle,  fossil  tree  near,  312.  318. 
New  Jersey,  cretaceous  strata  of,  256. 

,  Mastodon  giganteus  in,  144. 

New  red  sandstone,  distinction  from  old,  334. 

,  its  subdivisions,  335. 

of  United  States,  348. 

,  trap  of,  561 . 

New  York,  Devonian  strata  of,  430. 

,  Silurian  strata  of,  448. 

New  Zealand,  absence  of  quadrupeds,  165. 
Niagara  limestone,  Silurian  fossils  of, 449. 
— — ,  recent  shells  in  valley  of,  145. 
Nipadites  ellipticus,  217. 
Nodosarta,  chalk,  26. 
Noeggerath,  M.,  cited,  543. 
Noeggeralhia  cuneifolia,  360. 
Nomenclature,  changes  of,  93. 
Norfolk,  buried  forest,  134.  137.  154. 

,  drift,  132. 

Normandy,  chalk-cliffs  and  needles,  270. 
Northwich,  beds  of  salt  at,  345. 
Norwich  crag,  fluvio-marine,  155. 

,  sandpipes  near,  82. 

Nova  Scotia,  coal-seams  of  Cape  Breton,  315. 

,  fossil  forest  of  coal  in,  321. 

Nucula  Cobboldite,  156  ;  N.  Deshayesiana,  189. 
Nummulites,  whether  found  in  upper  eocene,  190. 
Nummulites  exponent,  232;    AT.  Icevigata,  216;    N. 

Puschi,  231. 

Nummulitic  formation,  230. 
Nyst,  M.,  cited,  189. 

OBOLUS  APOLiiNis,  Russia,  448. 

Oeynhausen,  M.  von,  on  Cornish  granite  veins,  574. 

Ohio,  Falls  of,  Devonian  coral-reef  of,  431. 

Old  red  sandstone,  415. 

,  in  Forfarshire,  605. 

,  trap  of,  563. 

Oldhamia  antiqua,  0.  radiata,  453. 
Olenus  micrurus,  Cambrian,  452. 
Oliva  Dufresnii?,  miocene,  179. 
Olot,  extinct  volcanos  near,  536. 
Omphyma  turbinatum,  Wenlock,  439. 
Onchus  tennistriatus,  Silurian,  436. 
Oolite,  292. 

and  lias,  origin  of,  320. 

,  inferior,  fossils  of,  315. 

in  France,  294. 

,  plutonic  rocks  of,  585. 

,  term  defined,  12. 

,  volcanic  rocks  of,  560. 

Oolitic  group  in  France,  294.  303. 

United  States,  331. 

Opltioderma  Egertoni,  lias,  321. 
Ophite  and  ophiolite,  477. 
Opossum,  part  of  jaw  of,  220. 
Orbigny,  M.  d',  cited,  254. 

,  on  fossils  of  nummulitic  limestone,  234. 

. ,  on  subdivisions  of  cretaceous  series,  238. 

,  on  Vienna  Basin  foraminifera,  180. 

Organic  remains,  criterion  of  age  of  formation,  98. 

,  test  of  age  of  volcanic  rocks,  525. 

Ormerod,  Mr.,  on  trias  of  Cheshire,  345. 

Orthis  elegantula,  435  ;  0.  grandis,  0.  tricenaria,  0. 

vespertilio,  444. 
Orthoceras  laterals,  412  ;   0.  Ludense,   0.  ventri- 

cosum,  438. 

Orthoclase,  or  common  felspar,  467. 
Osborne,  or  St.  Helen's  series,  I.  of  Wight,  193.  211. 
Osnabruck,  in  Westphalia,  tertiary  strata  of,  179. 
Ostrea  acuminata,  315  ;  0.  carinata,  0.  columba, 

0 -vesicular is ,11% ;  0.  distorta,W5  ;  O.  expansa,  0. 

deltoidea,  302  ;  0.  gregaria,  304  ;  0.  Marshii,  317. 


INDEX. 


651 


Otodus  obliquus,  tooth  of,  2!  6.  1 
Overlying,  term  applied  to  volcanic  rocks,  8. 
Owen,   Dr.   Dale,  on  oldest  fossiliferous  rocks  of 
Wisconsin,  457. 

,  Prof.,  cited,  162.  174.  263.  311.  313,  314.  340. 

,  on  amphitherium,  311. 

,  on  birds  in  New  Zealand,  166. 

,  on  bone-caves  in  England,  161 , 

,  on  footprints,  349. 

,  on  fossils  in  Australia,  163. 

— ,  on  fossil  monkey,  219. 

,  on  fossil  quadrupeds,  164. 

,  on  ichthyosaurus,  324. 

,  on  reptile  in  coal,  401. 

,  on  serpent  of  Brarklesham,  215. 

,  on  snake  of  Sheppey,  218. 

,  on  thecodont  saunans,  306. 

,  on  zeuglodou,  234. 

Oxford  clay,  305. 
Oyster  beds,  221. 

PACIFIC,  coral-reefs  of,  241. 

Palcechinus  gt'gas,  469. 

Pakeoniscus,  Permian,  outline  of,  356. 

Palceoniscus  comptus,  scale  of,  P.  elegant,  scale  of,  P. 

glaphyrus,  scale  of,  357. 
Palaeontology,  term  explained,  104. 
Pal&ophis  typhceus,  vertebras  of,  215. 
Palceosaurus  platyodon,  tooth  of,  358. 
Palaeotherium  magnum,  outline  of,  211. 
Palagonia,  dikes  at,  533. 
Palagonite  tuff,  474. 
Palermo,  caves  near,  74. 
Palraa,  Isle  of,  map  of,  499. 

,  structure  of,  498  —  512. 

Paludina  (Auvergne),  202 ;  P.  lenta,  29.  194. 

marginata,  P.  minuta,  133. 

(Mayence),  191  ;  P.  orbicularis,  210. 

Pampas,  extinct  quadrupeds  of,  164. 

Paradoxides  Bohemicus,  Cambrian,  454. 

Parasmilia  centralist  chalk,  407. 

Parallel  roads,  86. 

Pareto,  M.,  on  Carrara  marble,  619. 

Paris  basin,  93. 

Parka  decipiens  of  Forfarshire,  421. 

Parkinson,  Mr.,  on  crag,  111. 

Parrot,  Dr.  F.,  on  salt-lakes  of  Asia,  346. 

Patella  rugosa,  great  oolite,  309. 

Pear-Encrinile,  Bradford-clay,  307. 

Pearlstone,  volcanic  rock,  478. 

Pebbles  in  chalk,  242. 

Pecopteris  lonchitica,  coal,  364. 

Pecten  Beaveri,  247  ;  P.  islandicus,  131 ;  P.jacobceus, 

159. 

Pecten  papt/raceus,  389;  P.  quinquecostatus,  248. 
Pegmatite,  variety  of  granite,  567. 
Pentacrinus  Briareus,  lias,  321. 
Pentamerus  Knightii,  437  ;  P.  Icevis,  442. 
Pentland  hills,  Mr.  Maclaren  on,  132. 
Peperino,  volcanic  tuff,  478. 
Pepys,  Mr.,  cited,  41. 
Permian  flora,  distinct  from  that  of  coal,  358. 

formation  in  Thuringia,  359. 

group  described,  353. 

Perna  Mulleti,  lower  greensand,  259. 
Petrifaction  of  fossil  wood,  39. 

,  process  of,  43. 

Philippi,  Dr.,  on  fossil  shells  near  Naples,  118. 

,  on  Hesse  Cassel  beds,  187. 

. ,  on  marine  shells  in  caves  of  Sicily,  161. 

,  on  tertiary  shells  of  Sicily,  157. 

Phillips,  Prof.,  cited,  309.  319. 

,  on  cleavage,  610. 

,  on  terminology,  103. 

,Mr.  W.,  on  kaolin  of  China,  11. 

Phacopt  caudatus,  Silurian,  440. 
Phascolotherium  Bucklandi,  jaw  of,  313. 
Phasianella  Heddinglonensis,  coral-rag,  39. 


Phlebopteris  contigua,  oolite,  315. 
Pholadomyafidicula,  oolite,  316. 
Phonolite,  or  clinkstone,  476. 
Phorus  extensus,  London  clay,  219. 
Phosphate  of  lime,  252. 
Phragmcceras  ventricosum,  Ludlow,  438. 
Phryganea,  indusite  of,  202. 

,  (recent),  larva  of,  202. 

Phyllade  or  clay-slate,  597. 
Physa  Bristovii,  Purbeck,  296. 

columnaris,  P.  hypnorum  (recent),  29. 

Pictou,  Nova  Scotia,  calamites  near,  319. 
Pilla,  M.,  on  age  of  Carrara  marble,  619. 
Pisidium  amnicum,  133. 
Pisolitic  limestone  of  France,  236. 
Pitchstone,  or  retinite,  478. 
Placodus  gigas,  teeth  of,  337. 

Plagiostoma  giganteum,  319 ;  P.  Hoperi,  P.  spine- 
sum,  248. 

Planitz,  tripoli  of,  26. 

Planorbis  discus,  210  ;  P.  euomphalus,  29.  212. 
Plas  Newydd,  rock  altered  by  dike  near,  484. 
Plastic  clays,  220. 
Playfair,  cited,  45.  92.  i 

,  on  faults,  62. 

,  on  Huttonian  theory  of  stratification,  60. 

Plectrodus  mirabilts,  436. 
Plesiusaurus  dolichodeirus,  324. 
Pleurodictyum  problematicum,  429. 
Pleurotoma  attenuata,  217  ;  P.  rotata,31. 
Pleurotomaria  carinata,  P.  Jlamntigera,  410. 
Pleurotomaria  granulata,  P.  ornata,  316. 
Plieninger,  Professor,  on  triassic  mammifer,  342. 
Pliocene,  newer,  period,  126. 

,  newer,  strata,  153. 

strata  in  Sicily,  156. 

,  older,  in  United  States,  181. 

strata,  168. 

period,  volcanic  rocks  of,  533.  535. 

,  term  defined,  117. 

Plomb  du  Cantal,  described,  557. 
Plumbago  in  Massachusetts,  604. 
Plutonic  rocks,  7.  579. 

of  carboniferous  period,  586. 

of  oolite  and  lias,  585. 

,  recent  and  pliocene,  580. 

of  Silurian  period,  587. 

,  age  of,  how  tested,  579. 

Plutonic  and  sedimentary  rocks,  diagram  of,  582. 
Pluvial  action,  effects  of,  280. 
Podocarya,  fruit  of,  oolite,  314. 
Poggendorf,  cited,  601. 
Poikilitic  formation,  353. 

,  term  explained,  334. 

Polyccelia  profunda,  Permian,  407. 

Pomel,  M.,  on  mammalia  of  Auvergne,  204. 425. 

Ponza  Islands  in  Mediterranean,  490.  612. 

Porphyritic  granite,  568. 

Porphyry,  471,472. 

Portland,  Isle  of,  fossil  forest  in,  298. 

Portland  stone,  301. 

Portlock,  Col.,  on  Tyrone  Silurian  rocks,  447. 

Posidonia  minuta,  triassic,  336. 

Posidonomya?,  Richmond,  U.S.,  332. 

Becheri,  carboniferous,  414. 

Post- pliocene  formations,  117. 

,  period,  volcanic  rocks,  527. 

Potsdam  sandstone  at  Keeseville,  455. 

sandstone,  tracks  on,  456. 

—  sandstone  in  Canada,  450. 
Pottsville,  coal-seams  near,  394. 

,  footprints  of  reptile  near,  404. 

Pozzolana,  36. 

Pratt,  Mr.,  on  ammonites,  305. 

,  on  extinct  quadrupeds  of  Isle  of  Wight,  210. 

Precipitation  of  mineral  matter,  41. 
Predazzo,  altered  rocks  at,  586. 
Prestwich,  Mr.,  cited,  69. 


652 


INDEX. 


Prestwich,  Mr.,  on  Weald  denudation,  282. 

,  on  English  eocene  strata,  209.  213.  217.  220. 

— ,  on  coal-measures  of  Colebrook  Dale,  62. 388. 

Prevost,  M.  C.,  on  Paris  basin,  224,  225,  226. 

Productus  calvus,  P.  horridus,  355. 

Productus  antiquatus,  P.  semtrettculatns,  409. 

Progressive  development,  theory  of,  457. 

Protogine,  or  talcose  granite,  569. 

Psammodus  porosus,  tooth  of,  413. 

Psaronites  in  Germany  and  France,  360. 

Pseudocrinites  bifascfatus,  440. 

Pterichthys,  old  red,  423. 

Pterodactylus  crassirostris,  303. 

Pterophyllum  comptum,  315. 

Pterygotus  Angitcus,  419  ;  P.  problematicus,  420. 

Plychodus  decurrens,  tooth  of,  250. 

Puggaard,  Mr.,  on  Moen  drift,  286. 

Pumice,  473. 

Pupa  muscorum,  125  ;  P.  tridens,  30. 

Purbeck  beds,  292.  294. 

Purpuroidea  nodulata,  oolite,  309.  * 

Puy  de  Tartaret,  553. 

Puy  de  Poriou,  556. 

Puzzuoli,  elevation  and  depression  of  land  at,  529. 

,  post-pliocene  strata  at,  118. 

Pygopterus  mandibularis,  scale  of,  357. 
Pyrenees,  cretaceous  rocks  of,  585. 

•,  curvatures  of  strata  in,  58. 

,  granite  of,  600. 

,  nummulitic  formation  of,  231. 

Pyrocene,  or  augite,  469. 

Pyrula  reticulata,  coralline  crag,  173. 

QUADRUMANA  foSSll,  220. 

Quarrington  Hill,  basaltic  dike  near,  524. 

Quartz,  566. 

Quartzite,  or  quartz-rock,  596. 

RADiOLiTEsfoliaceus,  R.  radiosus,  254. 

Morloni,  chalk,  249. 

Radnorshire,  stratified  trap  of,  564. 
Rain-prints,  fossil  in  coal-shale,  387. 
Ramsay,  Prof.  A.C.,  on  denudation,  68. 

,  on  granite  in  Arran,  590. 

— ,  on  section  near  Bristol,  102. 

— — ,  on  Welsh  glaciers,  138. 

— ,  on  foliation  of  crystalline  schists,  616. 

,  on  Caradoc  sandstone,  442. 

Rastrites  peregrinus,  446. 
Recent  strata  defined,  118. 

,  near  Naples,  118. 

Redfield,  Mr.,  on  glacial  fauna  in  America,  140. 

,  on  fossil  fish,  351. 

Red  sandstone,  origin  of,  344. 

Red  Sea  and  Mediterranean,  distinct  species  in,  ICO. 

— ,  saltness  of,  347. 

Reptile  in  old  red  sandstone  of  Morayshire,  416. 

Reptiles,  carboniferous,  400,  401. 

of  lias,  323. 

,  fossil  eggs  of,  126. 

. ,  fossil,  of  Nova  Scotia  coal,  405. 

Reptilian  bone,  great  oolite,  311. 

footprints  in  coal-strata,  403. 

Retepora  flustracea,  355. 

Retinite,  or  pitchstone,  478. 

Rhine  valley,  loess  of,  122. 

Rhinoceros  leptorhinus,  tooth  of,  167. 

Rhynchonella  spinosa,  316  ;  R.  Wilsoni,  437. 

Rigi.near  Lucerne,  conglomerate  of,  180. 

Rimula  clathrata,  great  oolite,  309. 

Ripple-mark,  formation  of,  19. 

Rissoa  Chastelii,  eocene,  194. 

River-channels,  ancient,  399. 

River,  excavation  through  lava  by,  541. 

terraces,  85. 

Rock,  term  defined,  2. 

Rocks,  four  classes  of,  contemporaneous,  9. 

,  classification  of,  90. 


Rocks,  composed  of  fossil  zoophytes  and  shells,  24. 

,  trappean,  92. 

Roderburg,  extinct  volcano  of,  548. 

Rogers,  Prof.  Hv  D.,  on  coal-field,  United  States,  393. 

.cited,  396.417.431. 

,  on  reptilian  footprints  in  coal,  394. 

,  on  Devonian  rocks,  U.  S.,  431. 

,  Prof.    W.    B.,  on   oolitic   coal-field,    United 

States,  331.  393. 

,  on  Devonian  rocks,  U.  S.,  431. 

Rcme,  formations  at,  176.  535. 
Homer,  F.,  on  chalk  in  Texas,  256. 
Rosalinn,  chalk,  26. 
Rose,  Prof.  G.,  cited,  473.  563. 

,  on  hornblende,  468. 

Ross-shire,  denudation  in,  67. 
Rostellariamacroptera,  eocene,  219. 
Rothliegendes,  lower,  or  Permian,  359. 
Rubble,  term  explained,  81. 
Rupelmonde,  Upper  Eocene  beds,  189. 
Russia,  erratic  blocks  in,  l'/9. 

,  fossil  meteoric  iron  in,  152. 

,  Permian  rocks  in,  358. 

SAARBRUCK  coal-field,  reptiles  found  in,  401. 

St.  Abb's  Head,  curved  strata  near,  49. 

St.  Andrew's,  trap-rocks  in  cliffs  near,  561,  502. 

St.  Helena,  basalt  in,  487.  533. 

St.  Helens,  or  Osborne  series,  I.  of  Wight,  193.  211. 

St.  Lawrence,  gulf  of,  inland  beaches  and  cliff's,  78. 

St.  Mihiel,  France,  inland  cliffs  near,  77. 

St.  Paul,  Island  of,  512. 

St.  Peter's  Mount,  Maestricht,  fossils  in,  238. 

,  sandpipes  in,  83. 

Salisbury  Crag,  altered  strata  of,  485. 
Salt  rock,  origin  of,  345. 

,  precipitation  of,  345. 

,  at  North  wich,  345. 

.lakes  of  Asia,  346. 

Salter,  Mr.,  on  fossils  of  Caradoc  sandstone,  442. 

,  on  Caradoc  beds.  442. 

,  on  Silurian  fish,  436. 

— —  on  Silurian  rocks  of  Canada,  450. 
San  Lorenzo,  recent  strata  at,  121. 
Sandpipes  near  Maestricht,  83. 

,  near  Norwich,  82. 

,  or  sandgalls.  term  explained,  82. 

Sandstone,  with  cracks  in  Wealden,  264. 
Sandwich  Islands,  coral-reef  in,  242. 

,  volcanos  of,  493.  512.  532.  551. 

Sangatte,  near  Calais,  drift  of,  289. 
Sao  hirsuta,  metamorphoses  of,  454. 
Saucats,  near  Bordeaux,  faluns  of,  179. 
Saurians  of  lias,  324. 

,  thecodont,  358. 

Sdurichthys  apicalis,  tooth  of,  338. 
Saussure,  M.,  on  moraines,  148. 

,  on  vertical  conglomerates,  47. 

Savi,  M.,  on  Carrara  marble,  619. 
Saricava  rugosa,  pleistocene,  131. 
Saxony,  granite  in,  589. 
Scacchi,  M.,  on  post-pliocene  strata,  119. 
Scaphiles  tequalis,  246  ;  S.  gigas,  259. 
Scarborough,  oolitic  plants  of,  315. 
Schist,  hornblende  and  mica,  595,  596. 

,  argillaceous,  596. 

,  chlorite,  596. 

Schizodus  Schlotheimi,  354;  S.  truncatus,  hinge,  354. 

Schorl-rock  and  schorly  granite,  569. 

Scoresby  on  icebergs,  127. 

Scoriae,  473. 

Scotland,  carboniferous  traps  of,  561. 

,  northern  drift  in,  131. 

,  old  red  sandstone  of,  418. 

Scrope,  Mr.,  cited,  306.  547.  551.  554,  555.  558,  559. 

,  on  globular  structure  of  traps,  490. 

,  on  Ponza  Islands,  612. 


INDEX. 


653 


Scrope,  Mr.,  on  trachyte,  basalt,  and  tuff,  474.  526. 

,  on  central  France,  198. 

Seacliffs,  inland,  71. 
Section  of  Wealden,  274. 

,  of  white  chalk  from  England  to  France,  240. 

,  of  volcanic  rocks,  Auvergne,  552. 

Sedgwick,  Prof.,  cited,  362.  383. 

,  on  brecciated  limestone,  354. 

,  on  Caradoc  beds,  442. 

,  on  concretionary  magnesian  limestone,  37. 

,  on  Coniston  grit,  443. 

— — ,  on  Devonian  group,  423. 

• ,  on  garnets  in  altered  rock,  484. 

,  on  granite,  587.  589. 

,  on  Permian  sandstones,  357. 

,  on  joints  ;md  cleavage,  G07.  609.  615. 

,  on  mineral  composition  of  granite,  573. 

,  on  old  red  of  Devon  and  Cornwall,  423. 

,  on  structure  of  rocks,  607. 

— — ,  on  trap-rocks  of  Cumberland,  564. 

Segregation  in  mineral-veins,  627.' 

Semi-opal,  infusoria  in,  26. 

Seraphs  convolulum,  Barton  clay,  214. 

Serpentine,  478. 

Serpula  attached  to  Gryphcca,  22  ;  to  Spalangus,  23. 

carbonaria,  coal,  387. 

Xcrpulee  and  Bryozoa,  on  Encrinite,  308. 
S?rpnlae,  on  volcanic  rocks,  in  Sicily,  158. 
Sewalik  Hills,  freshwater  deposits,  183. 

.  miocene  strata  in,  183. 

Shale,  carbonaceous,  314. 

,  defined,  11. 

Shales  of  coal  near  Dudley,  600. 

Sharks,  teeth  of,  216. 

Sharpe,  Mr.  DM  on  mollusca  in  Silurian  strata,  449. 

,  on  slaty  cleavage,  615. 

,  on  upper  greensand,  251. 

Shells,  fossil,  passim. 

,  fossil,  useful  in  classification,  115. 

,  recent,  28,  29,  30.  141.  145. 

Sheppey,  Isle  of,  fossil  flora  of,  217. 
Sherringham,  mass  of  chalk  in  drift,  135. 
Shetland,  granite  of,  444.  571 .  573. 

,  hornblende-schist  of,  603. 

Shrewsbury,  coal-deposit  near,  387. 

Sicily,  Finme  Salso  in,  224. 

— — ,  inland  cliffs  in,  74. 

— ,  newer  pliocene  strata  of,  156. 

,  terraces  of  denudation  in,  75. 

Sidlaw  Hills,  trap  of  old  red  sandstone,  563. 
Siebengebirge,  igneous  rocks  of,  545. 
Sienna,  formations  at,  175. 
Sigillaria,  369.  371. 
Sigillaria  leevigata,  coal.  370. 
Siliceous  limestone  defined,  12. 

,  rocks  defined,  11. 

Sillhnan,  Prof.,  cited,  580. 
Silurian,  name  explained,  433. 

period,  plutonic  rocks  of,  587. 

rocks,  table  of,  434. 

, strata  of  deep  sea  origin,  451. 

strata  of  United  States,  448. 

. strata,  thickness  of,  446. 

. strata,  foot-tra<  ks  in,  456. 

volcanic  rocks,  563. 

Simpson.  Mr.,  on  ice-islands,  136. 

Siphonia  pyriformis,  upper  greensand.  2'  0. 

Siphon'itreta  unRuiculata .  Silurian,  448. 

Sivatherium,  extinct  ruminant,  183. 

Skapter  Jokul.  eruption  of,  526. 

Skye,  rocks  of,  485  586. 

— — ,  basaltic  columns  in,  487. 

,  dikes  in  Isle  of,  482. 

,  sandstone  in,  36. 

Slates  of  Devon,  cleavage  of,  610. 
Slaty  cleavage,  G09. 
Slick-nsides,  term  defined,  629. 


Smith,  Mr.,  of  Jordan  Hill,  on  pleistocene,  141. 

Snags,  fossil,  378. 

Snakes'  eggs,  fossil  at  Tonna  near  Gotha,  12C. 

Soissonnais  sands,  229. 

Solenhofen,  lithographic  stone  of,  303. 

Solfatara,  decomposition  of  rocks  in  the,  602. 

Somma,  530. 

,  lava  at,  482. 

S  >pwith,  Mr.  T.,  models  by,  57. 

Sorby,  Mr.,  on  mechanical  theory  of  cleavage,  610. 

Sortino,  cave  in  valley  of,  161. 

South  Devon  and  Cornwall,  old  red  of,  423. 

South  Downs,  view  of,  275. 

Sowerby,  Mr.  G.,  cited,  170. 

Spaccoforno,  inland  cliffs  at,  76. 

Spain,  volcanos  in,  6.  535. 

Spalacotherium,  Purbeck  mammifer,  296.  461. 

Spatangus  (recent),  23  ;  S.  radialus,  239. 

,  with  Serpula  attached,  23. 

Spezia,  gulf  of,  calcareous  rocks  in,  619. 
Sphcerexochus  m>rus,  Wenlock,  440. 
Sph&rulites  agariciformis,  chalk,  254. 
Sphenopteris  crenata,  364  ;  S.  gracilis,  265. 
Sp/rifer  disjimctus,  S.  Verneuilii,  425  ;  S.  glaber, 

S.  trisonalis,  410. 
,  mucronatus,  428  ;   S.  undulatus,  355  ;  S.  Wal- 

cottii,  320. 

Spirulina  stenostoma,  eocene,  228. 
Spirorbis  carbonarius,  coal,  387. 
Spitzbergen,  glaciers  of,  143. 
Spondylus  spinosus,  chalk,  248. 
Sponges  in  chalk,  250. 
Spongilla  of  Lamarck,  in  tripoli,  25. 

,  spicula  of,  tripoli,  25. 

Springs,  mineral.    See  Mineral  springs,  634. 

Staffa,  basaltic  columns  in,  487. 

Stauria  astrte&formis,  Silurian,  407. 

Steno  on  classification  of  rocks,  91. 

Sternbergia,  structure  of,  371. 

Stigmaria  in  fossil  forest,  Nova  Scotia,  380. 

Stigmaria  and  Sigillaria,  370. 

ficoides,  coal,  371. 

Stirling  Castle,  rock  of,  altered  by  dike,  485. 
Stockholm,  post-pliocene  beds  near,  119. 
Stokes,  Mr.,  on  petrifaction,  43. 
Stonesfield.  fossil  mammalia,  311.  313. 

slate,  310. 

Storton  Hill,  footprints  at, 339. 
Strata,  term  defined,  2. 

,  arrangement  of,  determined  by  fossils,  21,  22. 

— — ,  consolidation  of,  34. 

,  curved  and  vertical,  47.  58. 

,  elevation  of,  above  the  sea,  44. 

— ,  fossiliferous,  tabular  view  of,  105. 

,  horizontality  of,  15.  45. 

,  metam orphic  origin  of,  603. 

,  mineral  composition  of,  10. 

,  outcrop  of,  56. 

,  tertiary  classification  of,  110. 

Stratification,  forms  of,  13.  16.  47. 

,  unconformable,  59. 

Strickland,  Mr.,  on  new  red  sandstone,  333. 
Strike,  term  explained,  53. 
Stringocephaltis  Purtini,  Devonian,  427. 
Strom boli,  lava  of,  581. 

Strophomenn  depressa,  440  ;  S.  grandis,  444. 
Studer,  M.,  on  Swiss  Alps,  621. 

,  on  boulders  of  Jura,  150. 

Stutchbury,  M--.,  cited,  325.  358. 

Sub- Apennine  strata,  111.  174. 

Subsidence  in  drift  period,  142. 

Succinea  amphibia,  29  ;  S.  elongata,  125. 

Suffolk  crag,  169. 

Sullivan,  Capt.,  chart  of  Falkland  Islands,  88. 

Superga,  near  Turin,  tertiaries  of  Hill  of,  180. 

Superior,  Lake,  marl  in,  36. 

Superposition  of  aqueous  deposits,  97. 


654 


INDEX. 


Superposition  of  volcanic  rocks,  test  of  age,  327. 

Supracretaceous,  term  explained,  103.   . 

Sus  scrofa,  tooth  of,  167. 

Sussex  marble,  262. 

Swansea,  coal-measures  near,  362. 

,  stems  of  Sfgillaria  at,  376. 

Sweden,  alum-schists  of,  455. 
Swiss  Jura,  structure  of,  55. 
Sydney  coal-field,  Cape  Breton,  383. 
Syenite,  569. 
Syenitic  granite,  569. 
Synclinal  line,  term  denned,  48. 

TABLE  MOUNTAIN,  strata  horizontal  in,  45. 

,  granite-veins  in,  573. 

Table  of  fossiliferous  strata,  105. 

Tails  of  homocercal  and  heterocercal  fish,  3">6. 

Talcose  gneiss,  597. 

granite,  569. 

Tapirus  Americanus  (recent),  tooth  of,  167. 

Tartaret,  Puy  de,  cone  of,  553. 

Teeth  of  mammals,  fossil  and  recent,  166,  167,  168. 

220.  234.  312.  343. 

Telerpeton  Elginense,  old  red,  416. 
Tellina  obliqua,  pleistocene,  156. 
Temnechinus  excavatus,  coralline  crag,  173. 
Teneriffe,  Peak  of,  513.  515. 
Tentaculites  annulatus,  Silurian,  443. 
Terebellum  convolutwm,  T.fusrforme,  214. 
Terebralula  (Atrypa)  affinis,  438. 
, biplicala,   T.  carnea,   T.   Defrancii,  T.  octo- 

plicata,  T.  plicatilis,  T.  pumilus,  247. 
digona,  309;    T.fimbria,  316;  T.  hastata,  410; 

T.  lyrn,  252. 
navicula,  435 ;  T.  porrecta,  427  ;    T.  sella,  260  ; 

T.  Wilsoni,  437. 

Teredina  personata,  fossil  wood  bored  by,  24. 
Teredo  navalis  boring  wood,  24. 
Terra  del  Fuego,  146. 

,  Fucus  giganteus  in,  243. 

Tertiary,  term  explained,  110. 

deposits,  179.  190,191. 

, strata,  tabular  view  of,  105. 

Testudo  atlas,  of  Sewalik  Hills,  183. 

Texas,  chalk  in,  256. 

Thames  valley,  freshwater  deposits  in,  153. 

Tha.mnai.traa,  coral-rag,  304. 

Thanet  sands  described,  222. 

Thecodont  saurians,  344.  358. 

Thecodontosaurus,  tooth  of,  358. 

Thecosmilia  annularis,  304. 

Thelodus,  shagreen-scales  of,  436. 

Thirria,  M.,  on  oolitic  group  in  France,  330. 

Thuja  occidentalis,  in  stomach  of  mastodon,  145. 

Thurmann.M.  cited,  55.  281.  309. 

Tilestones,  434. 

Tilgate  Forest,  remains  in,  263. 

Till,  term  explained,  129. 

_— ,  origin  of,  129. 

Tin,  veins  of,  in  Cornwall,  628.  635. 

Tiverton,  trap-porphyry  near,  561. 

Tongrian  system  of  M.  Dumont,  189. 

Touraine,  faluns  of,  176. 

Trachyte,  470. 

.,  of  Hungary,  571. 

Trachytic  rocks,  older  than  basalt,  526. 
Transition,  term  explained,  92.  433. 
Trap,  term  explained,  464. 

. dike  in  Fifeshire,  563. 

. ?  globular  structure  of,  490. 

.,  intrusion  of,  between  strata,  486. 

, ,  various  ages  of,  561.  563. 

, ,  passage  of  granite  into,  570. 

. in  Radnorshire,  564. 

rocks,  relation  to  lava,  490. 

.  rocks,  lithological  character  of,  526. 

Trappean  rocks,  91. 


Traps  in  Lower  Eifel,  478.  548. 

Trap-tuff,  474. 

Travertin,  how  deposited,  31. 

Tree-ferns  in  Permian  formation,  360. 

Tree-ferns  (recent),  365. 

Trias,  or  new  red  sandstone,  334,  335.  337. 

,  in  Cheshire  and  Lancashire,  338.  315. 

,  subdivisions  of,  335. 

Trigonellites  latus,  oolite,  303. 
Trigonia  caudata,  260;  T.  gibbosa,  302. 
Trigonocarpum  oliveefurme,  T.  ovatum,  372. 
Trigonotreta  undulaia,  Permian,  355. 
Trilobites  in  Devonian  strata,  428. 

,  metamorphoses  of,  448.  454. 

,  of  lower  Silurian,  445. 

Tnloculma  inftata,  eocene,  228.  * 

Trimmer,  Mr.,  on  denudation  of  Wealden,  28G. 

,  on  sand-galls,  82. 

,  on  shells  in  drift  near  Menai  Straits,  137- 

Trmucleus  Caractaci,  T.  concentricus,  T.  ornatus, 

445. 

Trionyx,  fragment  of  carapace  of,  209. 
Tripoli  composed  of  infusoria,  24. 
Trochus  Anglicus,  lias,  39. 
Trophon  clnthralum,  pleistocene,  131. 
Tuff,  volcanic,  and  trap,  6.  474. 
Tuffs  on  Wrekin  and  Caer  Caradoc,  563. 
Tuomey,  Mr.,  cited,  235. 
Tupaia  Tana  (recent),  jaw  of,  312. 
Turner,  Dr.,  cited,  41,  42. 
Turrililes  costatus,  chalk,  247. 
Turritella  multisulcata,  Bracklesham,  217. 
Tuscany,  volcanic  rocks  of,  535. 
Tynedale  fault,  64. 
Tynemouth  Cliff,  limestone  at,  354. 
Typhis  pungens,  Barton,  214. 

UDDEVALLA,  post-pliocene  strata  at,  120. 

,  shells  of,  compared  with  those  near  Naples,  1 13. 

Underlying,  term  applied  to  granite,  8. 
Ungulite  grit  of  Ilussia,  447. 
Unto  littoralis  (recent),  28. 

,  Valdensis,  Wealden,  264. 

United  States,  coal-field  of,  391. 

,  cretaceous  formation  in,  255. 

,  Devonian  rocks  of,  430. 

,  Devonian  strata  in,  430. 

,  eocene  strata  in,  232. 

,  older  pliocene  and  miocene  formations  in,  181 . 

,  oolite  and  lias  of,  331 . 

,  Silurian  strata  of,  448. 

Upper  greensand,  251. 

Upsala,  strata  containing  Baltic  shells  near,  130. 

Ural  Mountains,  gold  of,  637. 

Ursus  spelceus,  tooth  of,  168. 

I 
VAL  DI  NOTO,  composition  of,  533. 

,  igneous  rocks  of,  491. 

,  inland  cliffs  in,  76. 

Valleys,  origin  of,  70. 

,  transverse  of  Weald,  277. 

Valorsine  granite,  574. 

Valvata,  pleistocene,  29. 

Veins,  mineral.     See  Mineral  veins,  626. 

Veinstones  in  parallel  layers,  631. 

Velay,  volcanos  of,  557. 

Venericardia  planicosta,  eocene,  215. 

Venetz,  M.,  on  Alpine  glaciers,  147. 

Ventriculites  radiatus,  chalk,  249. 

Verneuil,  M.  de,  on  Devonian  of  the  U.  S.,  430. 

,  on  horizontal  strata  in  Russia,  129. 

,  on  lower  Silurian,  U.  S.,  449. 

—r,  on  PentameiKS  Knightii,  437. 

,  on  Permian  flora,  357. 

Vertebrata,  fossil,  progress  of  discovery  of,  460. 

,  not  found  in  lower  Silurian,  458. 
Vesuvius,  eruption  of,  531. 


IXDEX. 


655 


Vicenza,  basaltic  columns  near,  489. 

Vidal,  Capt.,  survey  by,  499. 

Vienna  basin,  faluns  of,  180. 

Virginia.  U.  S.,  fossil  shells  in,  182. 

Virlet,  M.,  on  corrosion  of  rocks  by  gases,  602. 

— — ,  on  geology  of  Morea,  SCO. 

,  on  inland  cliffs,  73. 

Volcanic  dikes,  6.  430. 

mountains,  form  of,  5.  493. 

rocks,  age  of,  523. 

— — ,  analysis  of  minerals  in,  479- 

,  Cambrian,  564. 

,  composition  and  nomenclature  of,  466. 

,  described,  5.  464. 

of  Hungary,  540. 

of  post-pliocene  period,  527. 

of  Wales,  great  thickness  of,  448. 

,  Silurian,  563. 

,  test  of  age  of,  523. 

tuff,  6.  474. 

Volcanos  around  Olot  in  Catalonia,  538. 

,  extinct,  6.  535.  548.  550. 

in  Spain,  age  of,  541. 

,  newer,  of  Eifel,  545. 

of  Auvergne,  550. 

of  Canaries,  498. 

of  Java,  496. 

of  Sandwich  Isles,  493. 

Voltzia  heterophylla,  337. 
Valuta  ambigua,  V.  athleta,  214. 
.         Lamberti,  crag,  173. 

latrella,  217  ;  V.  nodosa,  219. 

Von  Buoh,  Baron,  cited,  474-  586,  587. 

,  on  boulders  of  Jura,  150. 

,  on  brown-coal,  192. 

,  on  Canary  Islands,  498. 

,  on  Cystideae,  443. 

,  on  land  rising,  45. 

\VACK£,  or  argillaceous  trap,  478. 

Walchia  piniformis,  Permian,  359. 

Wales,  ancient  glaciers  of,  137. 

Waller,  quoted,  93. 

Warren,  Dr.  J.  C.,  on  skeleton  of  Mastodon  gi- 

ganteus,  145. 

Waterhouse,  Mr.,  cited,  204.  313. 
Watt,  Mr.  G.,  experiments  on  fused  rocks,  532.601. 
Waves,  action  of,  on  limestone,  78. 


Weald  clay,  261. 

Weald  valley,  denuded  at  what  period,  282. 

Wealden,  term  explained,  260. 

,  the  fracture  and  upheaval  of,  281. 

,  extent  of  formation,  265. 

,  plants  and  animals  of,  2G3.  266. 

Webster,  Mr.  T.,  cited,  110.  294.  298. 
Wellington  Valley,  caves  in,  163. 
Wener  Lake,  horizontal  Silurian  strata  of,  45. 
Wenlock  formation,  432. 

,  shale,  441. 

Werner  on  classification  of  rocks,  91. 

,  on  mineral-veins,  626. 

,  on  volcanic  rocks,  467. 

Westerwald,  igneous  rocks  of,  543.  545. 

Westphalia,  tertiaries  of,  179. 

Westwood,  Mr.,  on  beetles  in  lias,  329.' 

Whin-Sil,  intrusion  of  trap  between  beds  at  the.  486. 

Whinstone,  or  trap,  478. 

White  chalk,  12.  240. 

White  Mountains,  granite-vein  in,  580. 

White  sand  of  Alum  Bay,  12. 

Whitestone,  or  furite,  570. 

Wigham,  Mr.,  on  fossils,  near  Norwich,  156. 

Wolverhampton,  fossil  forest  near,  377. 

Wood,  fossil  and  recent,  perforated  by  Mollusca,  24. 

,  from  Coalbrook  Dale,  structure  of,  372. 

,  from  the  coal,  microscopic  structure  of,  40. 

,  from  the  lias,  329. 

Wood,  Mr.  Searles,  on  Antwerp  crag  shells,  174. 

,  on  fossils  of  crag,  170. 

,  on  fossils  of  Isle  of  Wight,  212. 

,  on  number  of  shells  in  crag,  156. 

,  on  cetacea  of  crag,  174. 

,  cited,  178. 

Woodward,  Mr.,  on  mammoth  bones,  Norfolk,  154. 
Woolwich  beds  described,  221. 
Wrekin,  trap  of,  70. 
Wyman,  Dr.,  cited,  234. 

XIPHODON  gracile,  outline  of,  226. 
YORKSHIRE  Oolite,  plants  of,  314. 

ZAMIA  spiralis  (recent),  298. 
Zechstein,  352,  353. 

Zeuglodon  celoides,  tooth  and  vertebra  of,  324. 
Zoophytes,  fossil,  22,  158.  183.  302.  304.  407,  408,  426. 
439. 


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